IIgs stencil blitting is working!
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Scott Duensing
parent
436314f3f8
commit
5c04ad6b02
2 changed files with 83 additions and 41 deletions
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@ -25,15 +25,14 @@
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case on
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gen on
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GlobalData data
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ScTable ds 400 ; 400 bytes for 200 scanline offsets
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StTable ds 50 ; 50 bytes for 25 stencil table offsets
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MaTable ds 256 ; 4 bit stencil to mask word table
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VblRate ds 2 ; Either 5 or 6 depending on PAL or NTSC.
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VblTime ds 2 ; Integer Counter
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end
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;----------------------------------------
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; Blit an 8x8 block to (almost) anywhere on a surface.
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;----------------------------------------
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@ -136,10 +135,9 @@ t equ 5 ; Temp
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xc equ 7 ; X Counter
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yc equ 9 ; Y Counter
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stenO equ 11 ; Stencil Buffer Offset
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stenB equ 13 ; Stencil Buffer Data - bits - two bytes, but we only use one
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maskW equ 15 ; Actual mask bytes for pixels
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stenB equ 13 ; Stencil bit pattern
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jsubroutine (4:surface,4:tiles,4:stencil,2:sx,2:sy,2:tx,2:ty),16
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jsubroutine (4:surface,4:tiles,4:stencil,2:sx,2:sy,2:tx,2:ty),14
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using GlobalData
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; Find offset into tile memory
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@ -182,7 +180,6 @@ maskW equ 15 ; Actual mask bytes for pixels
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adc sx ; Add x position to address offset
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sta stenO ; Offset to start of mask data
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lda #0 ; Load 0 into X and Y counters
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sta xc
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sta yc
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@ -192,36 +189,23 @@ stenTop ldy stenO ; Load byte at stencil offset
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xba ; Shift it into the high byte
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sta stenB ; Put it in to the stencil byte
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; Convert stencil byte to mask word (4 pixels)
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blitTop ldx #4 ; How many pixels to process?
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lda #$ffff ; Initially, the mask word is all one bits
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sta maskW
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nextNib lda stenB ; Load stencil byte into accumulator
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asl a ; Shift first bit out of stencil byte into C
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sta stenB ; Update stencil byte
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bcc pixOn ; If C is clear, we draw the pixel (opposite of the mask data)
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lda maskW ; Load mask word into accumulator
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asl a ; Shift mask word over a pixel (4 bits)
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blitTop lda stenB ; Load stencil bit pattern
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tax ; Copy to x
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asl a ; Shift up a nibble for next time
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asl a
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asl a
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asl a
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; or #$0000 ; Do not draw pixel - mask it off
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sta maskW ; Store updated mask word
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jmp nextPix ; Start next pixel
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pixOn lda maskW ; Load mask word into accumulator
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asl a ; Shift mask word over a pixel (4 bits)
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asl a
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asl a
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asl a
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ora #$000f ; Draw pixel
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sta maskW ; Store updated mask word
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nextPix dex ; Decrement pixel counter in X
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bne nextNib ; Not zero? Do next nibble/pixel
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sta stenB ; Save for next pass
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txa ; Load original stencil byte back back
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xba ; Flip what we want into LSB
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and #$00f0 ; Mask off top nibble
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lsr a ; Shift it down to low nibble but multiplied by 2
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lsr a
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lsr a
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; lsr a
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tay ; Put it in y
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lda MaTable,y ; Load mask word
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; Draw four pixels
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lda maskW ; Load mask word
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xba ; Flip MSB and LSB
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ldy target ; Load Y register with target pixel offset
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and [surface],y ; AND target pixels with mask word
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ldy source ; Load Y register with source pixel offset
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@ -368,15 +352,13 @@ drawTop phy ; Keep Y for later
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end
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;===============================================================================================
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;
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;----------------------------------------
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; Arc3D line-drawing code
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; By Andy McFadden
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; Adapted from code by the FTA.
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;
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; Draws from (clpx0,clpy0) to (clpx1,clpy1) (output of a clipping routine).
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;
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;----------------------------------------
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asmDrawLine start
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x0 equ 1
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@ -881,7 +863,6 @@ __o13 equ *-2
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fx_done brl Exit
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;
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; common exit point
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;
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@ -1367,13 +1348,18 @@ StackPtr ds 2 ; Space for SP
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; Builds a table of scanline offsets
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;----------------------------------------
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asmStart start
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jsubroutine (2:id,2:hertz)
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stenB equ 1 ; Stencil byte (only lower nibble is used)
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stenC equ 3 ; Stencil byte counter
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maskW equ 5 ; Mask word
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jsubroutine (2:id,2:hertz),6
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using GlobalData
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ldy #0 ; Load 0 into y register
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lda #0 ; Load 0 into accumulator
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clc ; Clear carry flag
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tScan anop
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tScan anop ; Build scanline table
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sta ScTable,y ; Store accumulator in ScTable+x
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adc #160 ; Add 160 to accumulator (320 pixels / 2 pixels per byte)
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iny ; Increment y
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@ -1384,8 +1370,7 @@ tScan anop
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ldy #0 ; Load 0 into y register
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lda #0 ; Load 0 into accumulator
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clc ; Clear carry flag
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tSten anop
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tSten anop ; Build stencil cell table
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sta StTable,y ; Store accumulator in StencilTable+x
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adc #320 ; Add 320 to accumulator (8 lines * 40 bytes)
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iny ; Increment y
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@ -1393,6 +1378,52 @@ tSten anop
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cpy #50 ; Compare y to 50 (25 stencil cell offsets)
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bcc tSten ; Repeat Stencil Table Loop until we do all 25 cells
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; Convert stencil byte to mask word (4 pixels)
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clc ; Clear carry flag
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ldy #0 ; Load 0 into y register
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lda #0 ; Stencil bits starting point
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sta stenC
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tMask ldx #4 ; How many pixels to process?
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lda #$ffff ; Initially, the mask word is all one bits
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sta maskW
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lda stenC ; Put counter in bits
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xba ; Swap MSB and LSB
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asl a ; Shift mask word over a nibble
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asl a
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asl a
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asl a
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sta stenB
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nextNib lda stenB ; Load stencil byte into accumulator
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asl a ; Shift first bit out of stencil byte into C
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sta stenB ; Update stencil byte
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bcc pixOn ; If C is clear, we draw the pixel (opposite of the mask data)
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lda maskW ; Load mask word into accumulator
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asl a ; Shift mask word over a pixel (4 bits)
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asl a
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asl a
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asl a
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; or #$0000 ; Do not draw pixel - mask it off
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sta maskW ; Store updated mask word
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jmp nextPix ; Start next pixel
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pixOn lda maskW ; Load mask word into accumulator
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asl a ; Shift mask word over a pixel (4 bits)
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asl a
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asl a
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asl a
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ora #$000f ; Draw pixel
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sta maskW ; Store updated mask word
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nextPix dex ; Decrement pixel counter in X
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bne nextNib ; Not zero? Do next nibble/pixel
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xba ; Flip MSB and LSB
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sta MaTable,y ; Store accumulator (maskW) in table
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lda stenC ; Increment stencil bit pattern counter
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inc a
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sta stenC ; Store for the next pass
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iny ; Increment y - two bytes
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iny ; Increment y
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cpy #256 ; Compare y to 512 (128 stencil patterns)
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bcc tMask ; Repeat Mask Table Loop until we do all 128 bit patterns
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lda hertz ; Store refresh rate / 10 in VblCount and VblRate
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sta >VblRate
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@ -132,3 +132,14 @@
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.j
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rtl
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mend
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MACRO
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&lab jnibswap
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asl a
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adc #$80
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rol a
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asl a
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adc #$80
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rol a
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mend
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