JOLT Physics integrated. Hopefully.

CHANGELOG

@@ -18,6 +18,18 @@ API Changes
   database), and lfs.mkdir and lfs.rmdir act on its data overlay, so
   frameworks that list or create their own directories work packed.
 
+- Physics.  Any scene node can carry a rigid body on Jolt Physics:
+  static, kinematic (follows its node and pushes) or dynamic (drives its
+  node), shaped as a box, sphere, capsule, cylinder, a convex hull of the
+  node's mesh or the mesh's triangles; mass, friction, bounce,
+  velocities, forces and impulses; triggers; hinge, ball and slider
+  joints with limits; a raycast; onCollision and onTrigger callbacks.
+  The world steps at a fixed 60 Hz between animation and rendering and
+  pauses with the game.  New calls:  body*, joint*, physics*, and the
+  BODY_*, SHAPE_* and JOINT_* constants; see the Physics chapter.  Needs
+  SSE4.1 on x86 (2008 and later); the engine's first C++ (one wrapper
+  file and the library), statically linked, no runtime to install.
+
 - 3D scenes.  A game can draw a 3D scene between the disc video and the
   overlay:  primitive meshes and script-built geometry, materials with
   colour, textures from sprites, the disc or a loaded video, metallic and

docs/Manual.adoc

@@ -797,6 +797,95 @@ Put `.glb` files in the game directory like any other asset; `modelLoad`
 takes the same game-relative names as `spriteLoad`, and a packed `.game`
 carries them along.
 
+[#physics]
+=== Physics
+
+Bodies, joints, triggers and raycasts live in the 3D scene and ride on
+Jolt Physics. A body attaches to a node the way a mesh does; from then on
+the node and the body are one thing:
+
+* A *static* body (`BODY_STATIC`) stays where the node was when the body
+  was made: floors, walls, the cabinet.
+* A *kinematic* body (`BODY_KINEMATIC`) follows its node wherever the script
+  or an animation moves it, and pushes dynamic bodies out of its way without
+  being pushed itself: a paddle, a moving platform, a character's hand.
+* A *dynamic* body (`BODY_DYNAMIC`) is moved by the simulation and drives
+  its node: it falls, bounces, slides and gets pushed. Do not move its node
+  yourself; give it velocities, forces or impulses instead.
+
+Every body has a collision shape sized in world units and scaled by the
+node: a box, sphere, capsule or cylinder, a convex hull of the node's mesh
+(`SHAPE_HULL`, everything under the node, so a model instance's root works),
+or the mesh's exact triangles (`SHAPE_MESH`, static and kinematic bodies
+only). Units are metres, kilograms and seconds; gravity defaults to
+`0, -9.81, 0`.
+
+.Bodies for a crate stack and a paddle
+[source,lua]
+----
+floor = nodeNew()
+nodeSetMesh(floor, meshBox(14, 0.2, 14), stone)
+nodeSetPosition(floor, 0, -1.9, 0)
+bodyNew(floor, BODY_STATIC, SHAPE_BOX, 14, 0.2, 14)
+
+for i = 1, 6 do
+    local crate = nodeNew()
+    nodeSetMesh(crate, meshBox(0.6, 0.6, 0.6), wood)
+    nodeSetPosition(crate, -1, -1.5 + (i - 1) * 0.62, 0)
+    bodyNew(crate, BODY_DYNAMIC, SHAPE_BOX, 0.6, 0.6, 0.6)
+    bodySetMass(crate, 5)
+end
+
+paddle = nodeNew()
+nodeSetMesh(paddle, meshBox(0.3, 1.2, 1.6), red)
+nodeSetPosition(paddle, -4, -1.2, 0)
+bodyNew(paddle, BODY_KINEMATIC, SHAPE_BOX, 0.3, 1.2, 1.6)
+
+function onOverlayUpdate()
+    nodeMove(paddle, 0.06, 0, 0)   -- The kinematic paddle sweeps through the stack.
+    return OVERLAY_UPDATED
+end
+----
+
+.Mass matters
+A dynamic body's mass comes from its shape's volume at the density of
+water, so a box the size of a door weighs 140 kilograms and a nudge will
+not move it. Set `bodySetMass` on anything you want to feel light, and size
+impulses to the mass: an impulse of `mass * speed` sets that speed.
+
+.Timing
+The world steps at a fixed sixty times a second from the wall clock, after
+animations have posed their nodes and before the scene renders, so a
+kinematic body driven by an animation pushes with the right velocity.
+Pausing the game pauses physics; `physicsSetEnabled(false)` pauses it on
+its own.
+
+.Events and queries
+Define `onCollision(nodeA, nodeB, x, y, z, speed)` and Singe calls it once
+for each new contact, with the point and the speed the two bodies met at.
+A body made a trigger with `bodySetTrigger` pushes nothing but reports what
+enters and leaves it through `onTrigger(trigger, other, entered)`: a finish
+line, a doorway, a danger zone. `physicsRaycast` finds the first body along
+a ray; with `sceneUnproject` for the ray, that is mouse picking.
+
+.Joints
+`jointHinge`, `jointBall` and `jointSlider` connect two bodies, or a body
+and the world when the second node is `-1`: doors, pendulums, drawers.
+Hinges and sliders take limits. A positive hinge angle is a right-hand turn
+of the first node about the axis; a positive slider distance is along it.
+
+.Models
+Bodies on model instances work like any other: `bodyNew(instanceRoot,
+BODY_DYNAMIC, SHAPE_HULL)` wraps the whole model in a convex hull. Skinned
+characters are best driven kinematically with a capsule and left to push
+things rather than be pushed.
+
+.Where it runs
+Physics runs on the CPU and needs no GPU, but the library is built for
+SSE4.1 on x86 (2008 and later) and NEON on the Pi; a machine below that
+gets an error from the first `bodyNew`. The simulation uses every core
+but one, so a desktop steps in parallel and a Pi on a single thread.
+
 [#migrating]
 === Migrating from Singe 2.10
 
@@ -865,6 +954,9 @@ available to `controls.cfg` and to `Framework.singe` alike:
 | `RENDER_PIXELATED`, `RENDER_SMOOTH` | Arguments for `spriteQuality` / `videoQuality`.
 | `DISC_STOPPED`, `DISC_PLAYING`, `DISC_PAUSED`, `DISC_EJECTED` | Return values of `discGetState`.
 | `LIGHT_DIRECTIONAL`, `LIGHT_POINT`, `LIGHT_SPOT` | Arguments for `lightNew`.
+| `BODY_STATIC`, `BODY_DYNAMIC`, `BODY_KINEMATIC` | Body types for `bodyNew`.
+| `SHAPE_BOX`, `SHAPE_SPHERE`, `SHAPE_CAPSULE`, `SHAPE_CYLINDER`, `SHAPE_HULL`, `SHAPE_MESH` | Collision shapes for `bodyNew`.
+| `JOINT_HINGE`, `JOINT_BALL`, `JOINT_SLIDER` | Joint types (the `joint*` calls name them directly).
 | `SOUND_ERROR_INVALID`, `SOUND_REMOVE_HANDLE` | `-1`, what `soundPlay` returns when no channel is free.
 | `SINGE_VERSION_MAJOR`, `SINGE_VERSION_MINOR`, `SINGE_VERSION_STRING`, `SINGE_FRAMEWORK_VERSION` | The engine version, as integers, as a string (`"v3.00"`), and as the number `singeVersion()` returns.
 | `SINGE_DEAD_ZONE` | The `DEAD_ZONE` from `controls.cfg`.
@@ -1104,6 +1196,256 @@ Stops and forgets the animation. The nodes keep their last pose.
 *Since:* 3.00.
 *See also:* <<animationplay,animationPlay>>
 
+[#body]
+=== Body
+
+A body gives a scene node a place in the physics world. One body per node;
+static bodies stay put, kinematic bodies follow their node, dynamic bodies
+drive it. Every call here takes the node handle and raises an error when
+the node has no body. See <<physics,Physics>> for the model.
+
+[#bodynew]
+==== bodyNew
+
+[source,text]
+----
+bodyNew(node, type, shape, ...)
+bodyNew(node, BODY_DYNAMIC, SHAPE_BOX, width, height, depth)
+bodyNew(node, BODY_DYNAMIC, SHAPE_SPHERE, radius)
+bodyNew(node, BODY_DYNAMIC, SHAPE_CAPSULE, radius, height)
+bodyNew(node, BODY_DYNAMIC, SHAPE_CYLINDER, radius, height)
+bodyNew(node, BODY_DYNAMIC, SHAPE_HULL)
+bodyNew(node, BODY_STATIC, SHAPE_MESH)
+----
+
+Gives the node a body, placed where the node is now, with a shape sized in world units and scaled by the node's scale. A second call on the same node replaces the first.
+
+* `type` -- `BODY_STATIC`, `BODY_DYNAMIC` or `BODY_KINEMATIC`.
+* `shape` -- a primitive with its sizes (a capsule's or cylinder's height is the total, along Y), `SHAPE_HULL` for a convex hull of the node's mesh and everything under it, or `SHAPE_MESH` for the exact triangles (static and kinematic only).
+
+*Notes:* Mass comes from the shape's volume at the density of water; set it with `bodySetMass`. Changing the node's scale later does not resize the body. A dynamic body ignores its parent moving.
+
+*Since:* 3.00.
+*See also:* <<bodysetmass,bodySetMass>>, <<bodydelete,bodyDelete>>, <<physicssetgravity,physicsSetGravity>>
+
+.Example
+[source,lua]
+----
+-- A rubber ball dropped onto the scene.
+ball = nodeNew()
+nodeSetMesh(ball, meshSphere(0.3, 32), blue)
+nodeSetPosition(ball, 0, 3, 0)
+bodyNew(ball, BODY_DYNAMIC, SHAPE_SPHERE, 0.3)
+bodySetMass(ball, 0.5)
+bodySetBounce(ball, 0.7)
+----
+
+[#bodyapplyforce]
+==== bodyApplyForce
+
+[source,text]
+----
+bodyApplyForce(node, fx, fy, fz)
+bodyApplyForce(node, fx, fy, fz, px, py, pz)
+----
+
+A force for this step, in newtons, at the centre of mass or at a world point (which also spins the body). Dynamic bodies only.
+
+*Since:* 3.00.
+*See also:* <<bodyapplyimpulse,bodyApplyImpulse>>
+
+[#bodyapplyimpulse]
+==== bodyApplyImpulse
+
+[source,text]
+----
+bodyApplyImpulse(node, ix, iy, iz)
+bodyApplyImpulse(node, ix, iy, iz, px, py, pz)
+----
+
+An instant change of momentum (mass times speed), at the centre of mass or at a world point. What a hit, a kick or a launch wants. Dynamic bodies only.
+
+*Since:* 3.00.
+*See also:* <<bodyapplyforce,bodyApplyForce>>, <<bodysetvelocity,bodySetVelocity>>
+
+.Example
+[source,lua]
+----
+-- Flick whatever the mouse is over.
+local mx, my = mouseGetPosition(0)
+local ox, oy, oz = sceneUnproject(mx, my, 0)
+local fx, fy, fz = sceneUnproject(mx, my, 10)
+local hit, hx, hy, hz = physicsRaycast(ox, oy, oz, fx - ox, fy - oy, fz - oz)
+if hit then
+    bodyApplyImpulse(hit, 0, 3, 0, hx, hy, hz)
+end
+----
+
+[#bodydelete]
+==== bodyDelete
+
+[source,text]
+----
+bodyDelete(node)
+----
+
+Removes the body; the node stays. Joints on the body go with it. Deleting the node removes its body too.
+
+*Since:* 3.00.
+*See also:* <<bodynew,bodyNew>>
+
+[#bodygetangularvelocity]
+==== bodyGetAngularVelocity
+
+[source,text]
+----
+x, y, z = bodyGetAngularVelocity(node)
+----
+
+How fast the body spins about each world axis, in radians per second.
+
+*Returns:* Three numbers.
+
+*Since:* 3.00.
+*See also:* <<bodysetangularvelocity,bodySetAngularVelocity>>
+
+[#bodygetvelocity]
+==== bodyGetVelocity
+
+[source,text]
+----
+x, y, z = bodyGetVelocity(node)
+----
+
+How fast the body moves, in units per second.
+
+*Returns:* Three numbers.
+
+*Since:* 3.00.
+*See also:* <<bodysetvelocity,bodySetVelocity>>
+
+[#bodyisresting]
+==== bodyIsResting
+
+[source,text]
+----
+resting = bodyIsResting(node)
+----
+
+Whether the simulation has put the body to sleep because it stopped moving. Static and disabled bodies rest.
+
+*Returns:* Boolean.
+
+*Since:* 3.00.
+*See also:* <<bodysetenabled,bodySetEnabled>>
+
+[#bodysetangularvelocity]
+==== bodySetAngularVelocity
+
+[source,text]
+----
+bodySetAngularVelocity(node, x, y, z)
+----
+
+Sets the spin about each world axis, in radians per second, and wakes the body.
+
+*Since:* 3.00.
+*See also:* <<bodygetangularvelocity,bodyGetAngularVelocity>>
+
+[#bodysetbounce]
+==== bodySetBounce
+
+[source,text]
+----
+bodySetBounce(node, bounce)
+----
+
+Restitution from `0` (stops dead) to `1` (bounces back with everything it arrived with). Default `0.1`.
+
+*Since:* 3.00.
+*See also:* <<bodysetfriction,bodySetFriction>>
+
+[#bodysetenabled]
+==== bodySetEnabled
+
+[source,text]
+----
+bodySetEnabled(node, enabled)
+----
+
+Takes the body out of the world (it stops colliding and moving, its node stays put) and puts it back.
+
+*Since:* 3.00.
+*See also:* <<bodyisresting,bodyIsResting>>
+
+[#bodysetfriction]
+==== bodySetFriction
+
+[source,text]
+----
+bodySetFriction(node, friction)
+----
+
+Surface friction, `0` for ice upward; default `0.5`. The two touching bodies' values combine.
+
+*Since:* 3.00.
+*See also:* <<bodysetbounce,bodySetBounce>>
+
+[#bodysetmass]
+==== bodySetMass
+
+[source,text]
+----
+bodySetMass(node, kilograms)
+----
+
+Rescales a dynamic body's mass and inertia. Do this for anything meant to feel light: the default is the shape's volume at the density of water.
+
+*Since:* 3.00.
+*See also:* <<bodynew,bodyNew>>, <<bodyapplyimpulse,bodyApplyImpulse>>
+
+[#bodysettrigger]
+==== bodySetTrigger
+
+[source,text]
+----
+bodySetTrigger(node, trigger)
+----
+
+Makes the body a trigger: it pushes nothing and collides with nothing, but `onTrigger` reports what enters and leaves it. Usually a static box or sphere.
+
+*Since:* 3.00.
+*See also:* <<ontrigger,ontrigger>>, <<bodynew,bodyNew>>
+
+.Example
+[source,lua]
+----
+-- A finish line across the track.
+line = nodeNew()
+nodeSetPosition(line, 0, 0, -20)
+bodyNew(line, BODY_STATIC, SHAPE_BOX, 6, 3, 0.5)
+bodySetTrigger(line, true)
+
+function onTrigger(trigger, other, entered)
+    if trigger == line and other == car and entered then
+        lapDone()
+    end
+end
+----
+
+[#bodysetvelocity]
+==== bodySetVelocity
+
+[source,text]
+----
+bodySetVelocity(node, x, y, z)
+----
+
+Sets the velocity in units per second and wakes the body. Kinematic bodies take theirs from their node instead.
+
+*Since:* 3.00.
+*See also:* <<bodygetvelocity,bodyGetVelocity>>, <<bodyapplyimpulse,bodyApplyImpulse>>
+
 [#camera]
 === Camera
 
@@ -1901,6 +2243,100 @@ If you unload the currently selected font, the engine does not automatically pic
 *Since:* 2.00
 *See also:* <<fontload,fontLoad>>
 
+[#joint]
+=== Joint
+
+Joints connect two bodies, or a body and the world, and hand back a handle.
+Anchors and axes are given in world space at the moment the joint is made,
+with the bodies where they are then. Deleting either body deletes the
+joint.
+
+[#jointhinge]
+==== jointHinge
+
+[source,text]
+----
+joint = jointHinge(nodeA, nodeB, ax, ay, az, dx, dy, dz)
+----
+
+A hinge through the world point `(ax, ay, az)` along the axis `(dx, dy, dz)`: a door, a wheel, a lever. `nodeB` may be `-1` for the world.
+
+*Returns:* The joint handle.
+
+*Since:* 3.00.
+*See also:* <<jointsetlimits,jointSetLimits>>, <<jointdelete,jointDelete>>
+
+.Example
+[source,lua]
+----
+-- A door hinged to the world along its left edge, opening 100 degrees one way.
+door = nodeNew()
+nodeSetMesh(door, meshBox(1.4, 2.2, 0.1), wood)
+nodeSetPosition(door, 0, 0, 0)
+bodyNew(door, BODY_DYNAMIC, SHAPE_BOX, 1.4, 2.2, 0.1)
+bodySetMass(door, 8)
+hinge = jointHinge(door, -1, -0.7, 0, 0, 0, 1, 0)
+jointSetLimits(hinge, 0, 100)
+----
+
+[#jointball]
+==== jointBall
+
+[source,text]
+----
+joint = jointBall(nodeA, nodeB, ax, ay, az)
+----
+
+A ball-and-socket at the world point: the bodies may turn any way about it but not separate. A pendulum, a chain link, a ragdoll shoulder. `nodeB` may be `-1` for the world.
+
+*Returns:* The joint handle.
+
+*Since:* 3.00.
+*See also:* <<jointhinge,jointHinge>>
+
+[#jointslider]
+==== jointSlider
+
+[source,text]
+----
+joint = jointSlider(nodeA, nodeB, ax, ay, az, dx, dy, dz)
+----
+
+Lets the bodies slide relative to each other only along the axis through the anchor, keeping their orientation: a drawer, a piston, a lift. `nodeB` may be `-1` for the world.
+
+*Returns:* The joint handle.
+
+*Since:* 3.00.
+*See also:* <<jointsetlimits,jointSetLimits>>
+
+[#jointsetlimits]
+==== jointSetLimits
+
+[source,text]
+----
+jointSetLimits(joint, low, high)
+----
+
+Bounds a hinge's angle in degrees, or a slider's travel in world units, either side of where the joint started; `low` at or below `0`, `high` at or above. A positive hinge angle is a right-hand turn of `nodeA` about the axis; a positive slider distance is along the axis.
+
+*Notes:* A ball joint has no limits.
+
+*Since:* 3.00.
+*See also:* <<jointhinge,jointHinge>>, <<jointslider,jointSlider>>
+
+[#jointdelete]
+==== jointDelete
+
+[source,text]
+----
+jointDelete(joint)
+----
+
+Removes the joint; the bodies are free of each other again.
+
+*Since:* 3.00.
+*See also:* <<jointhinge,jointHinge>>
+
 [#keyboard]
 === Keyboard
 
@@ -3264,6 +3700,55 @@ Higher resolutions give finer control over sprite placement and sharper text at
 overlaySetResolution(discGetWidth(), discGetHeight())
 ----
 
+[#physicsref]
+=== Physics
+
+World-level calls. Physics is always initialised with the engine; there is
+nothing to enable before the first `bodyNew`. See <<physics,Physics>> in
+Game Development for how bodies, nodes and the frame fit together.
+
+[#physicsraycast]
+==== physicsRaycast
+
+[source,text]
+----
+node, hx, hy, hz, nx, ny, nz = physicsRaycast(x, y, z, dx, dy, dz)
+node, hx, hy, hz, nx, ny, nz = physicsRaycast(x, y, z, dx, dy, dz, maxDistance)
+----
+
+The first body along a ray from `(x, y, z)` in the direction `(dx, dy, dz)` (any length), within `maxDistance` (default `1000`). Triggers are hit too.
+
+*Returns:* The body's node, the hit point and the surface normal there, or `nil` when nothing is hit.
+
+*Since:* 3.00.
+*See also:* <<sceneunproject,sceneUnproject>>, <<bodyapplyimpulse,bodyApplyImpulse>>
+
+[#physicssetenabled]
+==== physicsSetEnabled
+
+[source,text]
+----
+physicsSetEnabled(enabled)
+----
+
+Pauses and resumes the simulation on its own; the game's pause does the same. Bodies hold still and keep their velocities.
+
+*Since:* 3.00.
+*See also:* <<physicssetgravity,physicsSetGravity>>
+
+[#physicssetgravity]
+==== physicsSetGravity
+
+[source,text]
+----
+physicsSetGravity(x, y, z)
+----
+
+The acceleration every dynamic body feels, in units per second squared. Default `0, -9.81, 0`; `0, 0, 0` for space.
+
+*Since:* 3.00.
+*See also:* <<bodynew,bodyNew>>
+
 [#scene]
 === Scene
 
@@ -4917,6 +5402,40 @@ function onMouseMoved(x, y, xr, yr, which)
 end
 ----
 
+[#oncollision]
+==== onCollision
+
+[source,text]
+----
+function onCollision(nodeA, nodeB, x, y, z, speed)
+    -- nodeA, nodeB: the two bodies' nodes
+    -- x, y, z: where they touched, in world space
+    -- speed: how fast they met, in units per second
+end
+----
+
+Called once for each new contact between two bodies after a physics step, never for a pair already touching. A crate landing, a ball hitting the cabinet, the player's car clipping a wall. Triggers report through `onTrigger` instead.
+
+*Since:* 3.00.
+*See also:* <<ontrigger,onTrigger>>, <<bodynew,bodyNew>>
+
+[#ontrigger]
+==== onTrigger
+
+[source,text]
+----
+function onTrigger(trigger, other, entered)
+    -- trigger: the trigger body's node
+    -- other: the node that entered or left it
+    -- entered: true on the way in, false on the way out
+end
+----
+
+Called when a body enters or leaves a trigger made with `bodySetTrigger`.
+
+*Since:* 3.00.
+*See also:* <<bodysettrigger,bodySetTrigger>>, <<oncollision,onCollision>>
+
 [#onoverlayupdate]
 ==== onOverlayUpdate
 

src/physics.h

@@ -52,6 +52,30 @@ typedef enum ShapeTypeE {
 } ShapeTypeE;
 
 
+// What happened during a step, drained by the engine after it:  a new contact between two bodies
+// (with the point and how fast they met), or a trigger being entered or left.
+typedef enum PhysicsEventTypeE {
+	PHYSICS_EVENT_COLLISION = 0,
+	PHYSICS_EVENT_ENTER     = 1,
+	PHYSICS_EVENT_LEAVE     = 2
+} PhysicsEventTypeE;
+
+typedef struct PhysicsEventS {
+	PhysicsEventTypeE type;
+	int32_t           nodeA;     // The trigger, for enter and leave
+	int32_t           nodeB;
+	Vec3T             point;
+	float             speed;
+} PhysicsEventT;
+
+
+typedef enum JointTypeE {
+	JOINT_HINGE  = 0,
+	JOINT_BALL   = 1,
+	JOINT_SLIDER = 2
+} JointTypeE;
+
+
 bool  bodyApplyForce(int32_t node, Vec3T force, const Vec3T *at);
 bool  bodyApplyImpulse(int32_t node, Vec3T impulse, const Vec3T *at);
 bool  bodyDelete(int32_t node);
@@ -65,10 +89,17 @@ bool  bodySetBounce(int32_t node, float bounce);
 bool  bodySetEnabled(int32_t node, bool enabled);
 bool  bodySetFriction(int32_t node, float friction);
 bool  bodySetMass(int32_t node, float kilograms);
+bool  bodySetTrigger(int32_t node, bool trigger);
 bool  bodySetVelocity(int32_t node, Vec3T velocity);
+bool  jointDelete(int32_t joint);
+int32_t jointNew(JointTypeE type, int32_t nodeA, int32_t nodeB, Vec3T anchor, Vec3T axis);
+bool  jointSetLimits(int32_t joint, float low, float high);
+bool  jointValid(int32_t joint);
 bool  physicsAvailable(void);
+int32_t physicsGetEvents(PhysicsEventT *events, int32_t maximum);
 bool  physicsInit(void);
 void  physicsQuit(void);
+bool  physicsRaycast(Vec3T origin, Vec3T direction, float maxDistance, int32_t *node, Vec3T *point, Vec3T *normal);
 void  physicsSetEnabled(bool enabled);
 void  physicsSetGravity(Vec3T gravity);
 void  physicsUpdate(bool advance);

src/physicsJolt.cpp

@@ -33,12 +33,23 @@
 #include <Jolt/Physics/PhysicsSystem.h>
 #include <Jolt/Physics/Body/BodyCreationSettings.h>
 #include <Jolt/Physics/Body/BodyLock.h>
+#include <Jolt/Physics/Body/BodyLockMulti.h>
 #include <Jolt/Physics/Collision/BroadPhase/BroadPhaseLayer.h>
 #include <Jolt/Physics/Collision/ObjectLayer.h>
 #include <Jolt/Physics/Collision/Shape/BoxShape.h>
 #include <Jolt/Physics/Collision/Shape/CapsuleShape.h>
 #include <Jolt/Physics/Collision/Shape/CylinderShape.h>
 #include <Jolt/Physics/Collision/Shape/SphereShape.h>
+#include <Jolt/Physics/Collision/Shape/ConvexHullShape.h>
+#include <Jolt/Physics/Collision/Shape/MeshShape.h>
+#include <Jolt/Physics/Constraints/HingeConstraint.h>
+#include <Jolt/Physics/Constraints/PointConstraint.h>
+#include <Jolt/Physics/Constraints/SliderConstraint.h>
+#include <Jolt/Physics/Collision/CastResult.h>
+#include <Jolt/Physics/Collision/RayCast.h>
+#include <Jolt/Physics/Collision/ContactListener.h>
+#include <mutex>
+#include <vector>
 extern "C" {
 #include "util.h"
 #include "scene.h"
@@ -57,6 +68,10 @@ extern "C" {
 #define DEFAULT_FRICTION      0.5f
 #define DEFAULT_BOUNCE        0.1f
 #define NO_HANDLE             -1
+#define MAX_EVENTS            512           // Per frame; the rest of a busy step is dropped
+#define DEFAULT_RAY_DISTANCE  1000.0f
+#define WORLD_NODE            -1            // A joint's other side fixed to the world
+#define DEGREES_TO_RADIANS(d) ((d) * (3.14159265358979323846f / 180.0f))
 
 
 // Two object layers:  what never moves and what may.  Static bodies never collide with each other.
@@ -109,11 +124,70 @@ namespace {
 		uint32_t    generation;     // The node's, so a reused handle is not mistaken for this body
 		JPH::BodyID id;
 		BodyTypeE   type;
+		bool        trigger;        // A sensor:  reports overlaps, pushes nothing
 		bool        enabled;        // In the world (bodySetEnabled)
 		bool        used;
 	};
 
 
+	struct WorldT;
+	extern WorldT *_world;
+	bool _isTrigger(JPH::BodyID id);
+
+
+	// Collects contacts from Jolt's job threads; the engine drains it after the step.
+	class ContactListenerT final : public JPH::ContactListener {
+	public:
+		std::mutex                 lock;
+		std::vector<PhysicsEventT> events;
+
+		void OnContactAdded(const JPH::Body &a, const JPH::Body &b, const JPH::ContactManifold &manifold, JPH::ContactSettings &settings) override {
+			PhysicsEventT event;
+			JPH::Vec3     relative;
+
+			(void)settings;
+			event.nodeA = (int32_t)(uint32_t)a.GetUserData();
+			event.nodeB = (int32_t)(uint32_t)b.GetUserData();
+			event.point = vec3((float)manifold.GetWorldSpaceContactPointOn1(0).GetX(), (float)manifold.GetWorldSpaceContactPointOn1(0).GetY(), (float)manifold.GetWorldSpaceContactPointOn1(0).GetZ());
+			relative    = a.GetLinearVelocity() - b.GetLinearVelocity();
+			event.speed = fabsf(relative.Dot(manifold.mWorldSpaceNormal));
+			if (a.IsSensor() || b.IsSensor()) {
+				event.type = PHYSICS_EVENT_ENTER;
+				if (b.IsSensor()) {
+					// The trigger comes first.
+					int32_t swap = event.nodeA;
+
+					event.nodeA = event.nodeB;
+					event.nodeB = swap;
+				}
+			} else {
+				event.type = PHYSICS_EVENT_COLLISION;
+			}
+			push(event);
+		}
+
+		void OnContactRemoved(const JPH::SubShapeIDPair &pair) override;
+
+		void push(const PhysicsEventT &event) {
+			std::lock_guard<std::mutex> guard(lock);
+
+			if (events.size() < MAX_EVENTS) {
+				events.push_back(event);
+			}
+		}
+	};
+
+
+	// A constraint between two bodies (or one body and the world).
+	struct JointRecordT {
+		JPH::Ref<JPH::Constraint> constraint;
+		JointTypeE                type;
+		int32_t                   nodeA;
+		int32_t                   nodeB;
+		bool                      used;
+	};
+
+
 	struct WorldT {
 		JPH::TempAllocatorImpl    *tempAllocator;
 		JPH::JobSystemThreadPool  *jobs;
@@ -121,8 +195,11 @@ namespace {
 		ObjectVsBroadPhaseFilterT  objectVsBroadPhase;
 		ObjectPairFilterT          objectPairs;
 		JPH::PhysicsSystem        *system;
+		ContactListenerT          *contacts;
 		BodyRecordT               *bodies;
 		int32_t                    bodyCount;
+		JointRecordT              *joints;
+		int32_t                    jointCount;
 		double                     accumulator;    // Seconds owed to the fixed step
 		uint64_t                   lastTick;
 		bool                       enabled;
@@ -132,15 +209,121 @@ namespace {
 	WorldT *_world = nullptr;
 
 
+	// A contact ending only matters for triggers:  the pair is reported as left.  This runs inside
+	// Jolt's step on a job thread, where taking a body lock deadlocks, so the lock-free interface
+	// reads the user data; the trigger flag comes from our records.
+	void ContactListenerT::OnContactRemoved(const JPH::SubShapeIDPair &pair) {
+		PhysicsEventT event;
+		JPH::uint64   userA   = _world->system->GetBodyInterfaceNoLock().GetUserData(pair.GetBody1ID());
+		JPH::uint64   userB   = _world->system->GetBodyInterfaceNoLock().GetUserData(pair.GetBody2ID());
+		bool          sensorA = _isTrigger(pair.GetBody1ID());
+		bool          sensorB = _isTrigger(pair.GetBody2ID());
+
+		if (!sensorA && !sensorB) {
+			return;
+		}
+		event.type  = PHYSICS_EVENT_LEAVE;
+		event.nodeA = (int32_t)(uint32_t)(sensorA ? userA : userB);
+		event.nodeB = (int32_t)(uint32_t)(sensorA ? userB : userA);
+		event.point = vec3(0.0f, 0.0f, 0.0f);
+		event.speed = 0.0f;
+		push(event);
+	}
+
+
+	JPH::RefConst<JPH::Shape> _buildMeshShape(int32_t node, ShapeTypeE shape, Vec3T position, QuatT rotation);
+	void         _collectGeometry(int32_t node, const Mat4T *toBody, JPH::Array<JPH::Vec3> &points, JPH::IndexedTriangleList &triangles, JPH::VertexList &vertices);
 	BodyRecordT *_find(int32_t node);
 	JPH::Quat    _fromQuat(QuatT q);
 	JPH::Vec3    _fromVec3(Vec3T v);
+	bool         _isTrigger(JPH::BodyID id);
 	void         _release(BodyRecordT *record);
 	QuatT        _toQuat(JPH::Quat q);
 	Vec3T        _toVec3(JPH::Vec3 v);
 	void         _trace(const char *fmt, ...);
 
 
+	// A convex hull or a triangle mesh from the geometry under a node (its own mesh and every
+	// descendant's, a model instance included), in the body's frame:  the node's world scale is
+	// baked in, its position and rotation are the body's.
+	JPH::RefConst<JPH::Shape> _buildMeshShape(int32_t node, ShapeTypeE shape, Vec3T position, QuatT rotation) {
+		JPH::Array<JPH::Vec3>    points;
+		JPH::VertexList          vertices;
+		JPH::IndexedTriangleList triangles;
+		Mat4T                    bodyWorld = mat4Compose(position, rotation, vec3(1.0f, 1.0f, 1.0f));
+		Mat4T                    toBody;
+
+		if (!mat4Invert(bodyWorld, &toBody)) {
+			return nullptr;
+		}
+		_collectGeometry(node, &toBody, points, triangles, vertices);
+		if (shape == SHAPE_HULL) {
+			JPH::ConvexHullShapeSettings settings(points);
+			JPH::Shape::ShapeResult      result;
+
+			if (points.size() < 4) {
+				utilTrace("Physics:  node %d has too little geometry for a hull.", node);
+				return nullptr;
+			}
+			result = settings.Create();
+			if (result.HasError()) {
+				utilTrace("Physics:  hull:  %s", result.GetError().c_str());
+				return nullptr;
+			}
+			return result.Get();
+		}
+		{
+			JPH::MeshShapeSettings  settings(vertices, triangles);
+			JPH::Shape::ShapeResult result;
+
+			if (triangles.empty()) {
+				utilTrace("Physics:  node %d has no triangles for a mesh shape.", node);
+				return nullptr;
+			}
+			result = settings.Create();
+			if (result.HasError()) {
+				utilTrace("Physics:  mesh:  %s", result.GetError().c_str());
+				return nullptr;
+			}
+			return result.Get();
+		}
+	}
+
+
+	// Gathers the node's mesh and its descendants' into the body's frame.
+	void _collectGeometry(int32_t node, const Mat4T *toBody, JPH::Array<JPH::Vec3> &points, JPH::IndexedTriangleList &triangles, JPH::VertexList &vertices) {
+		const float    *positions;
+		const uint32_t *indices;
+		int32_t         vertexCount;
+		int32_t         indexCount;
+		int32_t         mesh = nodeGetMesh(node);
+		int32_t         x;
+
+		if ((mesh != NO_HANDLE) && meshGetGeometry(mesh, &positions, &vertexCount, &indices, &indexCount)) {
+			Vec3T    position;
+			QuatT    rotation;
+			Vec3T    scale;
+			Mat4T    local;
+			uint32_t base = (uint32_t)vertices.size();
+
+			nodeGetWorldTransform(node, &position, &rotation, &scale);
+			local = mat4Multiply(*toBody, mat4Compose(position, rotation, scale));
+			for (x = 0; x < vertexCount; x++) {
+				Vec3T v = mat4TransformPoint(local, vec3(positions[x * 3], positions[x * 3 + 1], positions[x * 3 + 2]));
+
+				points.push_back(JPH::Vec3(v.x, v.y, v.z));
+				vertices.push_back(JPH::Float3(v.x, v.y, v.z));
+			}
+			for (x = 0; x + 2 < indexCount; x += 3) {
+				triangles.push_back(JPH::IndexedTriangle(base + indices[x], base + indices[x + 1], base + indices[x + 2]));
+			}
+		}
+		for (x = 0; x < nodeGetChildCount(node); x++) {
+			_collectGeometry(nodeGetChild(node, x), toBody, points, triangles, vertices);
+		}
+	}
+
+
 	// The record for a node's body, or NULL.  A record whose node was deleted (or reused) is
 	// released on the way.
 	BodyRecordT *_find(int32_t node) {
@@ -175,10 +358,29 @@ namespace {
 	}
 
 
-	// Takes the body out of the world and frees its slot.
+	// Whether a Jolt body is one of our triggers (by record, so a body being destroyed is safe).
+	bool _isTrigger(JPH::BodyID id) {
+		int32_t x;
+
+		for (x = 0; x < _world->bodyCount; x++) {
+			if (_world->bodies[x].used && (_world->bodies[x].id == id)) {
+				return _world->bodies[x].trigger;
+			}
+		}
+		return false;
+	}
+
+
+	// Takes the body out of the world (its joints first) and frees its slot.
 	void _release(BodyRecordT *record) {
 		JPH::BodyInterface &bodies = _world->system->GetBodyInterface();
+		int32_t             x;
 
+		for (x = 0; x < _world->jointCount; x++) {
+			if (_world->joints[x].used && ((_world->joints[x].nodeA == record->node) || (_world->joints[x].nodeB == record->node))) {
+				jointDelete(x);
+			}
+		}
 		if (record->enabled) {
 			bodies.RemoveBody(record->id);
 		}
@@ -329,8 +531,19 @@ bool bodyNew(int32_t node, BodyTypeE type, ShapeTypeE shape, float a, float b, f
 			height    = SDL_max(b * scale.y, MIN_DIMENSION);
 			joltShape = new JPH::CylinderShape(height / 2.0f, radius);
 			break;
+		case SHAPE_HULL:
+		case SHAPE_MESH:
+			if ((shape == SHAPE_MESH) && (type == BODY_DYNAMIC)) {
+				utilTrace("Physics:  a mesh shape can only be static or kinematic; use a hull for node %d.", node);
+				return false;
+			}
+			joltShape = _buildMeshShape(node, shape, position, rotation);
+			if (joltShape == nullptr) {
+				return false;
+			}
+			break;
 		default:
-			utilTrace("Physics:  shape %d is not available yet.", (int32_t)shape);
+			utilTrace("Physics:  unknown shape %d.", (int32_t)shape);
 			return false;
 	}
 	for (x = 0; x < _world->bodyCount; x++) {
@@ -440,6 +653,26 @@ bool bodySetMass(int32_t node, float kilograms) {
 }
 
 
+// A trigger (Jolt sensor) reports what enters and leaves it and pushes nothing.
+bool bodySetTrigger(int32_t node, bool trigger) {
+	BodyRecordT *record = _find(node);
+
+	if (record == nullptr) {
+		return false;
+	}
+	{
+		JPH::BodyLockWrite lock(_world->system->GetBodyLockInterface(), record->id);
+
+		if (!lock.Succeeded()) {
+			return false;
+		}
+		lock.GetBody().SetIsSensor(trigger);
+	}
+	record->trigger = trigger;
+	return true;
+}
+
+
 bool bodySetVelocity(int32_t node, Vec3T velocity) {
 	BodyRecordT *record = _find(node);
 
@@ -451,6 +684,131 @@ bool bodySetVelocity(int32_t node, Vec3T velocity) {
 }
 
 
+// ===== Joints =====
+
+bool jointDelete(int32_t joint) {
+	if (!jointValid(joint)) {
+		return false;
+	}
+	_world->system->RemoveConstraint(_world->joints[joint].constraint);
+	_world->joints[joint].constraint = nullptr;
+	_world->joints[joint].used       = false;
+	return true;
+}
+
+
+// A hinge (anchor and axis), ball (anchor) or slider (axis) between two bodies, or between a body
+// and the world when nodeB is -1.  Anchor and axis are in world space.  nodeA is Jolt's first
+// body (creating them the other way round mirrors the motion); see jointSetLimits for the sign
+// that implies.
+int32_t jointNew(JointTypeE type, int32_t nodeA, int32_t nodeB, Vec3T anchor, Vec3T axis) {
+	BodyRecordT               *a = _find(nodeA);
+	BodyRecordT               *b = (nodeB == WORLD_NODE) ? nullptr : _find(nodeB);
+	JPH::Ref<JPH::Constraint>  constraint;
+	JPH::Vec3                  direction;
+	JPH::Vec3                  normal;
+	int32_t                    x;
+
+	if ((_world == nullptr) || (a == nullptr) || ((nodeB != WORLD_NODE) && (b == nullptr))) {
+		return NO_HANDLE;
+	}
+	direction = _fromVec3(axis).NormalizedOr(JPH::Vec3::sAxisY());
+	normal    = direction.GetNormalizedPerpendicular();
+	{
+		JPH::BodyID ids[2] = { a->id, (b != nullptr) ? b->id : JPH::BodyID() };
+		JPH::BodyLockMultiWrite lock(_world->system->GetBodyLockInterface(), ids, (b != nullptr) ? 2 : 1);
+		JPH::Body *bodyA = lock.GetBody(0);
+		JPH::Body *bodyB = (b != nullptr) ? lock.GetBody(1) : &JPH::Body::sFixedToWorld;
+
+		if ((bodyA == nullptr) || (bodyB == nullptr)) {
+			return NO_HANDLE;
+		}
+		if (type == JOINT_HINGE) {
+			JPH::HingeConstraintSettings settings;
+
+			settings.mSpace       = JPH::EConstraintSpace::WorldSpace;
+			settings.mPoint1      = JPH::RVec3(anchor.x, anchor.y, anchor.z);
+			settings.mPoint2      = settings.mPoint1;
+			settings.mHingeAxis1  = direction;
+			settings.mHingeAxis2  = direction;
+			settings.mNormalAxis1 = normal;
+			settings.mNormalAxis2 = normal;
+			constraint = settings.Create(*bodyA, *bodyB);
+		} else if (type == JOINT_BALL) {
+			JPH::PointConstraintSettings settings;
+
+			settings.mSpace  = JPH::EConstraintSpace::WorldSpace;
+			settings.mPoint1 = JPH::RVec3(anchor.x, anchor.y, anchor.z);
+			settings.mPoint2 = settings.mPoint1;
+			constraint = settings.Create(*bodyA, *bodyB);
+		} else {
+			JPH::SliderConstraintSettings settings;
+
+			settings.mSpace       = JPH::EConstraintSpace::WorldSpace;
+			settings.mPoint1      = JPH::RVec3(anchor.x, anchor.y, anchor.z);
+			settings.mPoint2      = settings.mPoint1;
+			settings.mSliderAxis1 = direction;
+			settings.mSliderAxis2 = direction;
+			settings.mNormalAxis1 = normal;
+			settings.mNormalAxis2 = normal;
+			constraint = settings.Create(*bodyA, *bodyB);
+		}
+	}
+	if (constraint == nullptr) {
+		return NO_HANDLE;
+	}
+	_world->system->AddConstraint(constraint);
+	for (x = 0; x < _world->jointCount; x++) {
+		if (!_world->joints[x].used) {
+			break;
+		}
+	}
+	if (x == _world->jointCount) {
+		JointRecordT *grown = new JointRecordT[_world->jointCount + 1];
+
+		for (int32_t y = 0; y < _world->jointCount; y++) {
+			grown[y] = _world->joints[y];
+		}
+		delete[] _world->joints;
+		_world->joints = grown;
+		_world->jointCount++;
+	}
+	_world->joints[x].constraint = constraint;
+	_world->joints[x].type       = type;
+	_world->joints[x].nodeA      = nodeA;
+	_world->joints[x].nodeB      = nodeB;
+	_world->joints[x].used       = true;
+	return x;
+}
+
+
+// Limits:  degrees either side of the starting angle for a hinge (positive is a right-hand turn of
+// nodeA about the axis), distance along the axis for a slider (positive along it); low at or below
+// 0, high at or above.  Jolt measures both as its second body relative to its first, which is the
+// opposite of nodeA's own motion, so the range is mirrored on the way in.  A ball joint has none.
+bool jointSetLimits(int32_t joint, float low, float high) {
+	if (!jointValid(joint)) {
+		return false;
+	}
+	low  = SDL_min(low, 0.0f);
+	high = SDL_max(high, 0.0f);
+	if (_world->joints[joint].type == JOINT_HINGE) {
+		((JPH::HingeConstraint *)_world->joints[joint].constraint.GetPtr())->SetLimits(DEGREES_TO_RADIANS(-high), DEGREES_TO_RADIANS(-low));
+		return true;
+	}
+	if (_world->joints[joint].type == JOINT_SLIDER) {
+		((JPH::SliderConstraint *)_world->joints[joint].constraint.GetPtr())->SetLimits(-high, -low);
+		return true;
+	}
+	return false;
+}
+
+
+bool jointValid(int32_t joint) {
+	return (_world != nullptr) && (joint >= 0) && (joint < _world->jointCount) && _world->joints[joint].used;
+}
+
+
 // ===== World =====
 
 bool physicsAvailable(void) {
@@ -458,6 +816,26 @@ bool physicsAvailable(void) {
 }
 
 
+// Hands the engine the events the last step produced (up to maximum) and clears them.
+int32_t physicsGetEvents(PhysicsEventT *events, int32_t maximum) {
+	int32_t count = 0;
+
+	if (_world == nullptr) {
+		return 0;
+	}
+	{
+		std::lock_guard<std::mutex> guard(_world->contacts->lock);
+
+		while ((count < maximum) && (count < (int32_t)_world->contacts->events.size())) {
+			events[count] = _world->contacts->events[(size_t)count];
+			count++;
+		}
+		_world->contacts->events.clear();
+	}
+	return count;
+}
+
+
 // Brings Jolt up:  allocators, the type factory, a job pool sized to the machine, and an empty
 // world.  Refuses (returning false, 3D physics unavailable) on an x86 without SSE4.1 and 4.2, the
 // level the library was compiled for, rather than faulting on the first instruction.
@@ -483,6 +861,8 @@ bool physicsInit(void) {
 	_world->jobs   = new JPH::JobSystemThreadPool(JPH::cMaxPhysicsJobs, JPH::cMaxPhysicsBarriers, threads);
 	_world->system = new JPH::PhysicsSystem();
 	_world->system->Init(MAX_BODIES, 0, MAX_BODY_PAIRS, MAX_CONTACTS, _world->broadPhaseLayers, _world->objectVsBroadPhase, _world->objectPairs);
+	_world->contacts = new ContactListenerT();
+	_world->system->SetContactListener(_world->contacts);
 	_world->enabled = true;
 	utilTrace("Physics:  Jolt %d.%d.%d ready, %d job thread%s", JPH_VERSION_MAJOR, JPH_VERSION_MINOR, JPH_VERSION_PATCH, threads, (threads == 1) ? "" : "s");
 	return true;
@@ -501,7 +881,9 @@ void physicsQuit(void) {
 		}
 	}
 	SDL_free(_world->bodies);
+	delete[] _world->joints;
 	delete _world->system;
+	delete _world->contacts;
 	delete _world->jobs;
 	delete _world->tempAllocator;
 	delete _world;
@@ -512,6 +894,41 @@ void physicsQuit(void) {
 }
 
 
+// The nearest body along a ray (triggers included), with the hit point and surface normal.
+bool physicsRaycast(Vec3T origin, Vec3T direction, float maxDistance, int32_t *node, Vec3T *point, Vec3T *normal) {
+	JPH::RayCastResult result;
+	JPH::Vec3          dir;
+	JPH::RVec3         hit;
+
+	if (_world == nullptr) {
+		return false;
+	}
+	dir = _fromVec3(direction).NormalizedOr(JPH::Vec3::sZero());
+	if (dir.IsNearZero()) {
+		return false;
+	}
+	if (maxDistance <= 0.0f) {
+		maxDistance = DEFAULT_RAY_DISTANCE;
+	}
+	{
+		JPH::RRayCast ray(JPH::RVec3(origin.x, origin.y, origin.z), dir * maxDistance);
+
+		if (!_world->system->GetNarrowPhaseQuery().CastRay(ray, result)) {
+			return false;
+		}
+		hit = ray.GetPointOnRay(result.mFraction);
+	}
+	*node  = (int32_t)(uint32_t)_world->system->GetBodyInterface().GetUserData(result.mBodyID);
+	*point = vec3((float)hit.GetX(), (float)hit.GetY(), (float)hit.GetZ());
+	{
+		JPH::BodyLockRead lock(_world->system->GetBodyLockInterface(), result.mBodyID);
+
+		*normal = lock.Succeeded() ? _toVec3(lock.GetBody().GetWorldSpaceSurfaceNormal(result.mSubShapeID2, hit)) : vec3(0.0f, 1.0f, 0.0f);
+	}
+	return true;
+}
+
+
 // Pauses the simulation (bodies hold still) without losing it.
 void physicsSetEnabled(bool enabled) {
 	if (_world != nullptr) {

src/scene.c

@@ -111,6 +111,9 @@ typedef struct MeshS {
 	uint32_t       indexCount;
 	Vec3T          boundsMin;     // Of the vertices, for fitting the shadow map
 	Vec3T          boundsMax;
+	float         *positions;     // A CPU copy of the geometry (x, y, z per vertex) for physics shapes
+	uint32_t      *indices;
+	int32_t        vertexCount;
 	bool           skinned;
 	bool           used;
 } MeshT;
@@ -300,9 +303,21 @@ static int32_t _addMesh(const SceneVertexT *vertices, int32_t vertexCount, const
 		meshDelete(x);
 		return NO_HANDLE;
 	}
-	mesh->indexCount = (uint32_t)indexCount;
+	mesh->indexCount  = (uint32_t)indexCount;
-	mesh->skinned    = skinned;
+	mesh->vertexCount = vertexCount;
-	mesh->used       = true;
+	mesh->skinned     = skinned;
+	mesh->used        = true;
+	mesh->positions   = SDL_malloc(sizeof(float) * 3 * (size_t)vertexCount);
+	mesh->indices     = SDL_malloc(sizeof(uint32_t) * (size_t)indexCount);
+	if ((mesh->positions == NULL) || (mesh->indices == NULL)) {
+		utilDie("Out of memory keeping a mesh's geometry.");
+	}
+	for (x = 0; x < vertexCount; x++) {
+		mesh->positions[x * 3]     = vertices[x].position[0];
+		mesh->positions[x * 3 + 1] = vertices[x].position[1];
+		mesh->positions[x * 3 + 2] = vertices[x].position[2];
+	}
+	memcpy(mesh->indices, indices, sizeof(uint32_t) * (size_t)indexCount);
 	mesh->boundsMin  = vec3(vertices[0].position[0], vertices[0].position[1], vertices[0].position[2]);
 	mesh->boundsMax  = mesh->boundsMin;
 	for (x = 1; x < vertexCount; x++) {
@@ -1663,6 +1678,8 @@ bool meshDelete(int32_t mesh) {
 	if (_scene.meshes[mesh].indexBuffer != NULL) {
 		SDL_ReleaseGPUBuffer(_scene.device, _scene.meshes[mesh].indexBuffer);
 	}
+	SDL_free(_scene.meshes[mesh].positions);
+	SDL_free(_scene.meshes[mesh].indices);
 	memset(&_scene.meshes[mesh], 0, sizeof(MeshT));
 	for (x = 0; x < _scene.nodeCount; x++) {
 		if (_scene.nodes[x].used && (_scene.nodes[x].mesh == mesh)) {
@@ -1673,6 +1690,19 @@ bool meshDelete(int32_t mesh) {
 }
 
 
+// The mesh's geometry as kept on the CPU:  x, y, z per vertex and triangle indices.
+bool meshGetGeometry(int32_t mesh, const float **positions, int32_t *vertexCount, const uint32_t **indices, int32_t *indexCount) {
+	if (!meshValid(mesh)) {
+		return false;
+	}
+	*positions   = _scene.meshes[mesh].positions;
+	*vertexCount = _scene.meshes[mesh].vertexCount;
+	*indices     = _scene.meshes[mesh].indices;
+	*indexCount  = (int32_t)_scene.meshes[mesh].indexCount;
+	return true;
+}
+
+
 // Raw geometry from a script:  positions (3 per vertex), normals (3, may be NULL for flat
 // shading computed here), uvs (2, may be NULL), and triangle indices.
 int32_t meshNew(const float *positions, const float *normals, const float *uvs, int32_t vertexCount, const uint32_t *indices, int32_t indexCount) {
@@ -1940,6 +1970,15 @@ uint32_t nodeGetGeneration(int32_t node) {
 }
 
 
+// The node's mesh handle, or -1.
+int32_t nodeGetMesh(int32_t node) {
+	if (!nodeValid(node)) {
+		return NO_HANDLE;
+	}
+	return _scene.nodes[node].mesh;
+}
+
+
 const char *nodeGetName(int32_t node) {
 	if (!nodeValid(node) || (_scene.nodes[node].name == NULL)) {
 		return "";

src/scene.h

@@ -97,6 +97,7 @@ int32_t      meshBox(float width, float height, float depth);
 int32_t      meshCone(float radius, float height, int32_t segments);
 int32_t      meshCylinder(float radius, float height, int32_t segments);
 bool         meshDelete(int32_t mesh);
+bool         meshGetGeometry(int32_t mesh, const float **positions, int32_t *vertexCount, const uint32_t **indices, int32_t *indexCount);
 int32_t      meshNew(const float *positions, const float *normals, const float *uvs, int32_t vertexCount, const uint32_t *indices, int32_t indexCount);
 int32_t      meshNewVertices(const SceneVertexT *vertices, int32_t vertexCount, const uint32_t *indices, int32_t indexCount, bool skinned);
 int32_t      meshPlane(float width, float depth);
@@ -109,6 +110,7 @@ int32_t      nodeFind(int32_t root, const char *name);
 int32_t      nodeGetChild(int32_t node, int32_t index);
 int32_t      nodeGetChildCount(int32_t node);
 uint32_t     nodeGetGeneration(int32_t node);
+int32_t      nodeGetMesh(int32_t node);
 const char  *nodeGetName(int32_t node);
 int32_t      nodeGetParent(int32_t node);
 Vec3T        nodeGetPosition(int32_t node);

src/singe.c

@@ -496,6 +496,7 @@ static void         _pauseAllVideos(bool pause);
 static void         _processKey(bool down, int32_t keysym, int32_t scancode);
 static void         _progTrace(const char *fmt, ...) __attribute__((format(printf, 1, 2)));
 static int32_t      _pushVec3(lua_State *L, Vec3T v);
+static void         _physicsCallbacks(void);
 static SDL_Texture *_sceneVideoSource(int32_t player);
 static void         _pushConstants(lua_State *L);
 static void         _putPixel(int32_t x, int32_t y, uint32_t pixel);
@@ -540,6 +541,7 @@ static int32_t      apiBodySetBounce(lua_State *L);
 static int32_t      apiBodySetEnabled(lua_State *L);
 static int32_t      apiBodySetFriction(lua_State *L);
 static int32_t      apiBodySetMass(lua_State *L);
+static int32_t      apiBodySetTrigger(lua_State *L);
 static int32_t      apiBodySetVelocity(lua_State *L);
 static int32_t      apiCameraSet(lua_State *L);
 static int32_t      apiCameraSetOrthographic(lua_State *L);
@@ -577,6 +579,11 @@ static int32_t      apiFontQuality(lua_State *L);
 static int32_t      apiFontSelect(lua_State *L);
 static int32_t      apiFontToSprite(lua_State *L);
 static int32_t      apiFontUnload(lua_State *L);
+static int32_t      apiJointBall(lua_State *L);
+static int32_t      apiJointDelete(lua_State *L);
+static int32_t      apiJointHinge(lua_State *L);
+static int32_t      apiJointSetLimits(lua_State *L);
+static int32_t      apiJointSlider(lua_State *L);
 static int32_t      apiKeyboardGetLastDown(lua_State *L);
 static int32_t      apiKeyboardGetLastUp(lua_State *L);
 static int32_t      apiKeyboardGetMode(lua_State *L);
@@ -650,6 +657,7 @@ static int32_t      apiOverlayLine(lua_State *L);
 static int32_t      apiOverlayPlot(lua_State *L);
 static int32_t      apiOverlayPrint(lua_State *L);
 static int32_t      apiOverlaySetResolution(lua_State *L);
+static int32_t      apiPhysicsRaycast(lua_State *L);
 static int32_t      apiPhysicsSetEnabled(lua_State *L);
 static int32_t      apiPhysicsSetGravity(lua_State *L);
 static int32_t      apiSceneEnable(lua_State *L);
@@ -1088,6 +1096,9 @@ static void _callLua(const char *func, const char *sig, ...) {
 			case 'i':  // Int
 				lua_pushinteger(_global.luaContext, va_arg(vl, int));  // Promoted type for varargs.
 				break;
+			case 'b':  // Boolean (passed as an int)
+				lua_pushboolean(_global.luaContext, va_arg(vl, int32_t));
+				break;
 
 			case 's':  // String
 				lua_pushstring(_global.luaContext, va_arg(vl, char *));
@@ -2108,6 +2119,26 @@ static int32_t _pushVec3(lua_State *L, Vec3T v) {
 }
 
 
+// Hands the step's contacts and trigger overlaps to the script:  onCollision(nodeA, nodeB, x, y, z,
+// speed) and onTrigger(trigger, other, entered), when the script defines them.
+static void _physicsCallbacks(void) {
+	PhysicsEventT events[64];
+	int32_t       count;
+	int32_t       x;
+
+	count = physicsGetEvents(events, (int32_t)SDL_arraysize(events));
+	for (x = 0; x < count; x++) {
+		PhysicsEventT *event = &events[x];
+
+		if (event->type == PHYSICS_EVENT_COLLISION) {
+			_callLua("onCollision", "iidddd", event->nodeA, event->nodeB, (double)event->point.x, (double)event->point.y, (double)event->point.z, (double)event->speed);
+		} else {
+			_callLua("onTrigger", "iib", event->nodeA, event->nodeB, (event->type == PHYSICS_EVENT_ENTER) ? 1 : 0);
+		}
+	}
+}
+
+
 // A player's current frame for the 3D scene's video materials:  the disc's texture is already
 // updated for this frame; a loaded video is advanced here (drawing it on the overlay too is harmless).
 static SDL_Texture *_sceneVideoSource(int32_t player) {
@@ -2200,6 +2231,12 @@ static void _pushConstants(lua_State *L) {
 	lua_setglobal(L, "SHAPE_HULL");
 	lua_pushinteger(L, SHAPE_MESH);
 	lua_setglobal(L, "SHAPE_MESH");
+	lua_pushinteger(L, JOINT_HINGE);
+	lua_setglobal(L, "JOINT_HINGE");
+	lua_pushinteger(L, JOINT_BALL);
+	lua_setglobal(L, "JOINT_BALL");
+	lua_pushinteger(L, JOINT_SLIDER);
+	lua_setglobal(L, "JOINT_SLIDER");
 
 	lua_pushinteger(L, -1);
 	lua_setglobal(L, "SOUND_ERROR_INVALID");
@@ -2819,7 +2856,7 @@ static int32_t apiBodyIsResting(lua_State *L) {
 }
 
 
-// bodyNew(node, type, shape, a [, b [, c]]):  BODY_* and SHAPE_*; a, b, c size the shape
+// bodyNew(node, type, shape [, a [, b [, c]]]):  BODY_* and SHAPE_*; a, b, c size the primitive shapes
 static int32_t apiBodyNew(lua_State *L) {
 	int32_t node;
 	int32_t type;
@@ -2898,6 +2935,14 @@ static int32_t apiBodySetMass(lua_State *L) {
 }
 
 
+// bodySetTrigger(node, bool):  a trigger reports what enters and leaves it (onTrigger) and pushes nothing
+static int32_t apiBodySetTrigger(lua_State *L) {
+	_argCheck(L, "bodySetTrigger", 2, 2);
+	bodySetTrigger(_argBody(L, "bodySetTrigger", 1), _argBoolean(L, "bodySetTrigger", 2));
+	return 0;
+}
+
+
 // bodySetVelocity(node, x, y, z)
 static int32_t apiBodySetVelocity(lua_State *L) {
 	_argCheck(L, "bodySetVelocity", 4, 4);
@@ -3457,6 +3502,95 @@ static int32_t apiFontUnload(lua_State *L) {
 }
 
 
+// joint = jointBall(nodeA, nodeB, ax, ay, az):  nodeB -1 fixes to the world; anchor in world space
+static int32_t apiJointBall(lua_State *L) {
+	int32_t nodeA;
+	int32_t nodeB;
+	int32_t joint;
+
+	_argCheck(L, "jointBall", 5, 5);
+	nodeA = _argBody(L, "jointBall", 1);
+	nodeB = _argInteger(L, "jointBall", 2);
+	if ((nodeB != -1) && !bodyExists(nodeB)) {
+		_luaDie(L, "jointBall", "Node %d has no body.", nodeB);
+	}
+	joint = jointNew(JOINT_BALL, nodeA, nodeB, _argVec3(L, "jointBall", 3), vec3(0.0f, 1.0f, 0.0f));
+	if (joint < 0) {
+		_luaDie(L, "jointBall", "Unable to create the joint.");
+	}
+	lua_pushinteger(L, joint);
+	return 1;
+}
+
+
+// jointDelete(joint)
+static int32_t apiJointDelete(lua_State *L) {
+	int32_t joint;
+
+	_argCheck(L, "jointDelete", 1, 1);
+	joint = _argInteger(L, "jointDelete", 1);
+	if (!jointDelete(joint)) {
+		_luaDie(L, "jointDelete", "No joint %d.", joint);
+	}
+	return 0;
+}
+
+
+// joint = jointHinge(nodeA, nodeB, ax, ay, az, dx, dy, dz):  anchor and axis in world space; nodeB -1 is the world
+static int32_t apiJointHinge(lua_State *L) {
+	int32_t nodeA;
+	int32_t nodeB;
+	int32_t joint;
+
+	_argCheck(L, "jointHinge", 8, 8);
+	nodeA = _argBody(L, "jointHinge", 1);
+	nodeB = _argInteger(L, "jointHinge", 2);
+	if ((nodeB != -1) && !bodyExists(nodeB)) {
+		_luaDie(L, "jointHinge", "Node %d has no body.", nodeB);
+	}
+	joint = jointNew(JOINT_HINGE, nodeA, nodeB, _argVec3(L, "jointHinge", 3), _argVec3(L, "jointHinge", 6));
+	if (joint < 0) {
+		_luaDie(L, "jointHinge", "Unable to create the joint.");
+	}
+	lua_pushinteger(L, joint);
+	return 1;
+}
+
+
+// jointSetLimits(joint, low, high):  degrees for a hinge, distance for a slider
+static int32_t apiJointSetLimits(lua_State *L) {
+	int32_t joint;
+
+	_argCheck(L, "jointSetLimits", 3, 3);
+	joint = _argInteger(L, "jointSetLimits", 1);
+	if (!jointSetLimits(joint, (float)_argNumber(L, "jointSetLimits", 2), (float)_argNumber(L, "jointSetLimits", 3))) {
+		_luaDie(L, "jointSetLimits", "Joint %d has no limits to set.", joint);
+	}
+	return 0;
+}
+
+
+// joint = jointSlider(nodeA, nodeB, ax, ay, az, dx, dy, dz):  slides along the axis through the anchor; nodeB -1 is the world
+static int32_t apiJointSlider(lua_State *L) {
+	int32_t nodeA;
+	int32_t nodeB;
+	int32_t joint;
+
+	_argCheck(L, "jointSlider", 8, 8);
+	nodeA = _argBody(L, "jointSlider", 1);
+	nodeB = _argInteger(L, "jointSlider", 2);
+	if ((nodeB != -1) && !bodyExists(nodeB)) {
+		_luaDie(L, "jointSlider", "Node %d has no body.", nodeB);
+	}
+	joint = jointNew(JOINT_SLIDER, nodeA, nodeB, _argVec3(L, "jointSlider", 3), _argVec3(L, "jointSlider", 6));
+	if (joint < 0) {
+		_luaDie(L, "jointSlider", "Unable to create the joint.");
+	}
+	lua_pushinteger(L, joint);
+	return 1;
+}
+
+
 // scancode = keyboardGetLastDown()  Cleared every frame.
 static int32_t apiKeyboardGetLastDown(lua_State *L) {
 	_luaTrace(L, "keyboardGetLastDown", "%d", _global.keyboardLastDown);
@@ -4628,6 +4762,32 @@ static int32_t apiOverlaySetResolution(lua_State *L) {
 }
 
 
+// node, hx, hy, hz, nx, ny, nz = physicsRaycast(x, y, z, dx, dy, dz [, maxDistance]):  nil when nothing is hit
+static int32_t apiPhysicsRaycast(lua_State *L) {
+	Vec3T   origin;
+	Vec3T   direction;
+	float   maxDistance = 0.0f;
+	int32_t node;
+	Vec3T   point;
+	Vec3T   normal;
+
+	_argCheck(L, "physicsRaycast", 6, 7);
+	origin    = _argVec3(L, "physicsRaycast", 1);
+	direction = _argVec3(L, "physicsRaycast", 4);
+	if (lua_gettop(L) >= 7) {
+		maxDistance = (float)_argNumber(L, "physicsRaycast", 7);
+	}
+	if (!physicsRaycast(origin, direction, maxDistance, &node, &point, &normal)) {
+		lua_pushnil(L);
+		return 1;
+	}
+	lua_pushinteger(L, node);
+	_pushVec3(L, point);
+	_pushVec3(L, normal);
+	return 7;
+}
+
+
 // physicsSetEnabled(bool):  pauses the simulation without losing it
 static int32_t apiPhysicsSetEnabled(lua_State *L) {
 	_argCheck(L, "physicsSetEnabled", 1, 1);
@@ -6173,6 +6333,7 @@ void singe(SDL_Window *window, SDL_Renderer *renderer, SDL_GPUDevice *device, Co
 	lua_register(_global.luaContext, "bodySetEnabled",              apiBodySetEnabled);               // 3.00
 	lua_register(_global.luaContext, "bodySetFriction",             apiBodySetFriction);              // 3.00
 	lua_register(_global.luaContext, "bodySetMass",                 apiBodySetMass);                  // 3.00
+	lua_register(_global.luaContext, "bodySetTrigger",              apiBodySetTrigger);               // 3.00
 	lua_register(_global.luaContext, "bodySetVelocity",             apiBodySetVelocity);              // 3.00
 	lua_register(_global.luaContext, "colorBackground",             apiColorBackground);              // 1.xx
 	lua_register(_global.luaContext, "colorForeground",             apiColorForeground);              // 1.xx
@@ -6216,6 +6377,11 @@ void singe(SDL_Window *window, SDL_Renderer *renderer, SDL_GPUDevice *device, Co
 	lua_register(_global.luaContext, "fontToSprite",                apiFontToSprite);                 // 1.xx
 	lua_register(_global.luaContext, "fontUnload",                  apiFontUnload);                   // 2.00
 
+	lua_register(_global.luaContext, "jointBall",                   apiJointBall);                    // 3.00
+	lua_register(_global.luaContext, "jointDelete",                 apiJointDelete);                  // 3.00
+	lua_register(_global.luaContext, "jointHinge",                  apiJointHinge);                   // 3.00
+	lua_register(_global.luaContext, "jointSetLimits",              apiJointSetLimits);               // 3.00
+	lua_register(_global.luaContext, "jointSlider",                 apiJointSlider);                  // 3.00
 	lua_register(_global.luaContext, "keyboardGetLastDown",         apiKeyboardGetLastDown);          // 2.10
 	lua_register(_global.luaContext, "keyboardGetLastUp",           apiKeyboardGetLastUp);            // 2.10
 	lua_register(_global.luaContext, "keyboardGetMode",             apiKeyboardGetMode);              // 1.xx RDG
@@ -6291,6 +6457,7 @@ void singe(SDL_Window *window, SDL_Renderer *renderer, SDL_GPUDevice *device, Co
 	lua_register(_global.luaContext, "overlayPrint",                apiOverlayPrint);                 // 1.xx
 	lua_register(_global.luaContext, "overlaySetResolution",        apiOverlaySetResolution);         // 2.00
 
+	lua_register(_global.luaContext, "physicsRaycast",              apiPhysicsRaycast);               // 3.00
 	lua_register(_global.luaContext, "physicsSetEnabled",           apiPhysicsSetEnabled);            // 3.00
 	lua_register(_global.luaContext, "physicsSetGravity",           apiPhysicsSetGravity);            // 3.00
 	lua_register(_global.luaContext, "sceneEnable",                 apiSceneEnable);                  // 3.00
@@ -6849,6 +7016,7 @@ void singe(SDL_Window *window, SDL_Renderer *renderer, SDL_GPUDevice *device, Co
 			// 3D scene
 			modelUpdate(!_global.frozen);
 			physicsUpdate(!_global.frozen);
+			_physicsCallbacks();
 			sceneUpdateVideo(_sceneVideoSource);
 			sceneTexture = sceneRender();
 			if (sceneTexture != NULL) {

testScripts/README.md

@@ -24,3 +24,5 @@ screenshot or two and quits by itself; the results are in screenshots/.
 | scene7.singe    | 7     | 18.6b | Shadows:  sun, sun and spot together, a point light inside |
 | scene8.singe    | 8     | 18    | An arcade cabinet from primitives with the disc on screen  |
 | scene9.singe    | 9     | 19.2  | Physics:  a crate stack, a ball, a kinematic paddle        |
+| scene10.singe   | 10    | 19.3  | Physics:  a trigger volume, collision callbacks, a raycast pick |
+| scene11.singe   | 11    | 19.4  | Physics:  a hull down a ramp, a mesh torus, hinge, ball and slider joints |

testScripts/games.dat

@@ -98,4 +98,26 @@ GAMES = {
 		DEVELOPER   = "Test",
 		PUBLISHER   = "Test",
 	},
+	{
+		TITLE       = "Physics2",
+		SCRIPT      = "testScripts/scene10.singe",
+		VIDEO       = "Singe/menuBackground.mkv",
+		DESCRIPTION = "A trigger volume, collision callbacks and a raycast pick.",
+		YEAR        = 2026,
+		GENRE       = "Test",
+		PLATFORM    = "Singe",
+		DEVELOPER   = "Test",
+		PUBLISHER   = "Test",
+	},
+	{
+		TITLE       = "Physics3",
+		SCRIPT      = "testScripts/scene11.singe",
+		VIDEO       = "Singe/menuBackground.mkv",
+		DESCRIPTION = "A hull rolling down a ramp, a mesh torus, a hinged door, a pendulum, a slider.",
+		YEAR        = 2026,
+		GENRE       = "Test",
+		PLATFORM    = "Singe",
+		DEVELOPER   = "Test",
+		PUBLISHER   = "Test",
+	},
 }

testScripts/scene10.singe

@@ -0,0 +1,122 @@
+-- Physics stage 3:  a trigger volume in the crates' path, collision callbacks, and a raycast
+-- through the middle of the overlay that flicks whatever it hits.
+local font   = fontLoad("Singe/FreeSansBold.ttf", 28)
+local frames = 0
+local entered, left, collisions, lastSpeed, picks = 0, 0, 0, 0, 0
+
+fontSelect(font)
+discPlay()
+sceneEnable(true)
+sceneSetBackground(18, 18, 30, 255)
+sceneSetAmbient(70, 70, 85)
+
+local floorLook = materialNew()
+materialSetColor(floorLook, 120, 110, 100)
+materialSetRoughness(floorLook, 0.9)
+local crateLook = materialNew()
+materialSetColor(crateLook, 200, 140, 60)
+local ballLook = materialNew()
+materialSetColor(ballLook, 60, 140, 230)
+local paddleLook = materialNew()
+materialSetColor(paddleLook, 230, 60, 40)
+local zoneLook = materialNew()
+materialSetColor(zoneLook, 80, 255, 120, 70)
+materialSetBlend(zoneLook, true)
+materialSetUnlit(zoneLook, true)
+local markLook = materialNew()
+materialSetColor(markLook, 255, 255, 80)
+materialSetEmissive(markLook, 120, 120, 0)
+
+local floor = nodeNew()
+nodeSetMesh(floor, meshBox(14, 0.2, 14), floorLook)
+nodeSetPosition(floor, 0, -1.9, 0)
+bodyNew(floor, BODY_STATIC, SHAPE_BOX, 14, 0.2, 14)
+
+local crates = {}
+for i = 1, 4 do
+	local crate = nodeNew()
+	nodeSetMesh(crate, meshBox(0.6, 0.6, 0.6), crateLook)
+	nodeSetPosition(crate, -1.0, -1.5 + (i - 1) * 0.62, 0)
+	bodyNew(crate, BODY_DYNAMIC, SHAPE_BOX, 0.6, 0.6, 0.6)
+	crates[i] = crate
+end
+
+local ball = nodeNew()
+nodeSetMesh(ball, meshSphere(0.35, 32), ballLook)
+nodeSetPosition(ball, 0.2, 1.5, 0.3)
+bodyNew(ball, BODY_DYNAMIC, SHAPE_SPHERE, 0.35)
+bodySetBounce(ball, 0.5)
+
+-- The trigger:  a translucent green volume to the right of the stack.
+local zone = nodeNew()
+nodeSetMesh(zone, meshBox(1.6, 1.6, 2.4), zoneLook)
+nodeSetPosition(zone, 1.8, -1.0, 0)
+bodyNew(zone, BODY_STATIC, SHAPE_BOX, 1.6, 1.6, 2.4)
+bodySetTrigger(zone, true)
+
+local paddle = nodeNew()
+nodeSetMesh(paddle, meshBox(0.3, 1.2, 1.6), paddleLook)
+nodeSetPosition(paddle, -4.0, -1.2, 0)
+bodyNew(paddle, BODY_KINEMATIC, SHAPE_BOX, 0.3, 1.2, 1.6)
+
+-- A marker placed where the pick ray hits.
+local mark = nodeNew()
+nodeSetMesh(mark, meshSphere(0.08, 12), markLook)
+nodeSetVisible(mark, false)
+
+local sun = lightNew(LIGHT_DIRECTIONAL)
+nodeSetPosition(sun, -3, 6, 4)
+nodeLookAt(sun, 0, 0, 0)
+lightSetIntensity(sun, 1.2)
+lightSetShadow(sun, true)
+
+local camera = nodeNew()
+nodeSetPosition(camera, 1.0, 1.6, 6.5)
+nodeLookAt(camera, 0.2, -0.6, 0)
+cameraSet(camera)
+
+function onCollision(a, b, x, y, z, speed)
+	collisions = collisions + 1
+	lastSpeed = speed
+end
+
+function onTrigger(trigger, other, isEntering)
+	if isEntering then
+		entered = entered + 1
+	else
+		left = left + 1
+	end
+	debugPrint(string.format("trigger %d %s node %d", trigger, isEntering and "entered by" or "left by", other))
+end
+
+function onOverlayUpdate()
+	frames = frames + 1
+	overlayClear()
+	fontPrint(20, 20, string.format("Physics %d  hits %d (%.1f)  in %d out %d  picks %d", frames, collisions, lastSpeed, entered, left, picks))
+	if frames >= 60 and frames < 150 then
+		nodeMove(paddle, 0.06, 0, 0)
+	end
+	if frames % 30 == 0 and frames <= 240 then
+		-- A ray from the camera through the overlay's centre; flick whatever it hits upward.
+		local w, h = sceneGetSize()
+		local ox, oy, oz = sceneUnproject(w / 2, h / 2, 0)
+		local fx, fy, fz = sceneUnproject(w / 2, h / 2, 10)
+		local hit, hx, hy, hz = physicsRaycast(ox, oy, oz, fx - ox, fy - oy, fz - oz)
+		if hit then
+			picks = picks + 1
+			nodeSetVisible(mark, true)
+			nodeSetPosition(mark, hx, hy, hz)
+			if hit ~= floor and hit ~= zone and hit ~= paddle then
+				bodyApplyImpulse(hit, 0, 3, 0, hx, hy, hz)
+			end
+			debugPrint(string.format("pick node %d at %.2f %.2f %.2f", hit, hx, hy, hz))
+		end
+	end
+	if frames == 50 or frames == 130 or frames == 220 then
+		singeScreenshot()
+	end
+	if frames == 250 then
+		debugPrint(string.format("RESULT collisions=%d entered=%d left=%d picks=%d", collisions, entered, left, picks))
+		singeQuit()
+	end
+end

testScripts/scene11.singe

@@ -0,0 +1,125 @@
+-- Physics stage 4:  the Duck as a convex hull rolling down a ramp, a torus as a static mesh shape
+-- the ball rolls around, a swinging door on a hinge with limits, a pendulum on a ball joint, and
+-- a crate on a slider.
+local font   = fontLoad("Singe/FreeSansBold.ttf", 28)
+local frames = 0
+
+fontSelect(font)
+discPlay()
+sceneEnable(true)
+sceneSetBackground(18, 18, 30, 255)
+sceneSetAmbient(70, 70, 85)
+
+local floorLook = materialNew()
+materialSetColor(floorLook, 120, 110, 100)
+materialSetRoughness(floorLook, 0.9)
+local rampLook = materialNew()
+materialSetColor(rampLook, 90, 100, 130)
+local doorLook = materialNew()
+materialSetColor(doorLook, 160, 90, 40)
+local ballLook = materialNew()
+materialSetColor(ballLook, 60, 140, 230)
+local ringLook = materialNew()
+materialSetColor(ringLook, 220, 200, 60)
+materialSetMetallic(ringLook, 0.8)
+materialSetRoughness(ringLook, 0.35)
+local frameLook = materialNew()
+materialSetColor(frameLook, 40, 40, 50)
+local crateLook = materialNew()
+materialSetColor(crateLook, 200, 140, 60)
+
+local floor = nodeNew()
+nodeSetMesh(floor, meshBox(16, 0.2, 16), floorLook)
+nodeSetPosition(floor, 0, -1.9, 0)
+bodyNew(floor, BODY_STATIC, SHAPE_BOX, 16, 0.2, 16)
+
+-- A ramp, and the Duck as a convex hull rolling down it.
+local ramp = nodeNew()
+nodeSetMesh(ramp, meshBox(3.0, 0.2, 2.2), rampLook)
+nodeSetPosition(ramp, -3.4, -1.0, -1.0)
+nodeSetRotation(ramp, 0, 0, -28)
+bodyNew(ramp, BODY_STATIC, SHAPE_BOX, 3.0, 0.2, 2.2)
+
+local duck = modelInstance(modelLoad("testScripts/Models/Duck.glb"))
+nodeSetPosition(duck, -4.4, 0.6, -1.0)
+nodeSetRotation(duck, 0, 90, 0)
+nodeSetScale(duck, 0.6)
+bodyNew(duck, BODY_DYNAMIC, SHAPE_HULL)
+bodySetFriction(duck, 0.4)
+
+-- A torus lying on the floor as a static triangle mesh; the ball rolls around inside it.
+local ring = nodeNew()
+nodeSetMesh(ring, meshTorus(1.2, 0.25, 40), ringLook)
+nodeSetPosition(ring, 2.6, -1.55, 0.6)
+bodyNew(ring, BODY_STATIC, SHAPE_MESH)
+
+local ball = nodeNew()
+nodeSetMesh(ball, meshSphere(0.3, 32), ballLook)
+nodeSetPosition(ball, 2.6, 1.2, 0.6)
+bodyNew(ball, BODY_DYNAMIC, SHAPE_SPHERE, 0.3)
+bodySetBounce(ball, 0.4)
+
+-- A door hinged to the world along its left edge, limited to swing 100 degrees one way.
+local post = nodeNew()
+nodeSetMesh(post, meshBox(0.15, 2.4, 0.15), frameLook)
+nodeSetPosition(post, -1.0, -0.6, 1.4)
+bodyNew(post, BODY_STATIC, SHAPE_BOX, 0.15, 2.4, 0.15)
+
+local door = nodeNew()
+nodeSetMesh(door, meshBox(1.4, 2.2, 0.1), doorLook)
+nodeSetPosition(door, -0.1, -0.62, 1.4)
+bodyNew(door, BODY_DYNAMIC, SHAPE_BOX, 1.4, 2.2, 0.1)
+bodySetMass(door, 8)
+local hinge = jointHinge(door, -1, -0.85, -0.62, 1.4, 0, 1, 0)
+jointSetLimits(hinge, 0, 100)
+
+-- A pendulum:  a ball hanging from a point in the air.
+local bob = nodeNew()
+nodeSetMesh(bob, meshSphere(0.25, 24), ballLook)
+nodeSetPosition(bob, 1.4, 1.6, -1.6)
+bodyNew(bob, BODY_DYNAMIC, SHAPE_SPHERE, 0.25)
+jointBall(bob, -1, 0.2, 2.6, -1.6)
+
+-- A crate on a slider along X, pushed sideways at the start.
+local rail = nodeNew()
+nodeSetMesh(rail, meshBox(3.0, 0.08, 0.08), frameLook)
+nodeSetPosition(rail, 0.6, 0.9, -3.0)
+local crate = nodeNew()
+nodeSetMesh(crate, meshBox(0.5, 0.5, 0.5), crateLook)
+nodeSetPosition(crate, -0.6, 0.9, -3.0)
+bodyNew(crate, BODY_DYNAMIC, SHAPE_BOX, 0.5, 0.5, 0.5)
+local slider = jointSlider(crate, -1, -0.6, 0.9, -3.0, 1, 0, 0)
+jointSetLimits(slider, 0, 2.4)
+bodySetVelocity(crate, 3, 0, 0)
+
+local sun = lightNew(LIGHT_DIRECTIONAL)
+nodeSetPosition(sun, -3, 6, 4)
+nodeLookAt(sun, 0, 0, 0)
+lightSetIntensity(sun, 1.2)
+lightSetShadow(sun, true)
+
+local camera = nodeNew()
+nodeSetPosition(camera, 0.8, 2.4, 7.5)
+nodeLookAt(camera, 0, -0.4, -0.5)
+cameraSet(camera)
+cameraSetPerspective(52, 0.1, 100)
+
+function onOverlayUpdate()
+	frames = frames + 1
+	overlayClear()
+	fontPrint(20, 20, "Physics joints and hulls, frame " .. frames)
+	if frames == 40 then
+		-- Kick the door and the pendulum.
+		bodyApplyImpulse(door, 0, 0, -60, 0.5, -0.62, 1.45)
+		bodyApplyImpulse(bob, 6, 0, 0)
+	end
+	if frames == 30 or frames == 90 or frames == 180 then
+		singeScreenshot()
+	end
+	if frames == 200 then
+		local dx, dy, dz = nodeGetWorldPosition(duck)
+		local cx = nodeGetWorldPosition(crate)
+		debugPrint(string.format("RESULT duck %.2f %.2f %.2f  crate x %.2f", dx, dy, dz, cx))
+		singeQuit()
+	end
+end