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dos33fsprogs/graphics/hgr/budge3d/ship_cube.s
Vince Weaver d29d6649e5 budge3d: re-arrange some more
2023-01-06 23:33:41 -05:00

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;============================================================================
; Disassembly of a module generated by Bill Budge's 3-D Graphics System and
; Game Tool.
;
; The tool itself is copyright 1980 California Pacific Computer Co. Modules
; may be marketed and sold so long as they provide a credit notice.
;
; The HRCG (code and font) is credited to Christopher Espinosa.
;===========================================================================
; Disassembly by Andy McFadden, using 6502bench SourceGen v1.6.
; Last updated 2020/03/11
;
; The manual refers to "points" and "lines" rather than "vertices" and
; "edges". For consistency the same nomenclature is used here.
;
; Two shapes are defined: the space shuttle model from the manual, and a
; simple cube 11 units on a side. The module is configured for XOR drawing
; This makes extensive use of self-modifying code. Labels that begin with an
; underscore indicate self-modification targets.
; Note from Vince Weaver
; + I've taken the disassembly and am converting it to assembly language
; I guess it might make more sense to get an assembly language kernel
; from the program, but I'm going to modify the BASIC anyway
;===========================================================================
;
; You can define up to 16 shapes. Their parameters are stored in the various
; arrays:
;
; CODE_arr+N: 0 (do nothing), 1 (transform & draw), 2 (erase previous,
; transform, draw new), 3 (erase).
; X_arr+N: X coordinate of center (0-255).
; Y_arr+N: Y coordinate of center (0-191).
; SCALE_arr+N: scale factor, 0-15. 15 is full size, 0 is 1/16th.
; XROT_arr+N: rotation about X axis, 0-27. 0 is no rotation, 27 is just shy
; of 360 degrees.
; YROT_arr+N: rotation about Y axis.
; ZROT_arr+N: rotation about Z axis.
; SX_arr+N: (output) X coordinate of last point drawn.
; SY_arr+N: (output) Y coordinate of last point drawn.
;
; The code entry points are:
; RESET: initializes graphics module, clears the screen, switches display
; to primary hi-res page.
; CLR: clears both hi-res screens and switches to primary hi-res page.
; HIRES: turns on primary hi-res page.
; CRUNCH: primary animation function.
;
; The "CRUNCH" function:
; - erases objects whose CODE value is 2 or 3
; - computes new transformations for objects whose CODE value is 1 or 2
; - draws objects whose CODE value is 1 or 2
; - flips the display to the other page
;============================================================================
.include "zp.inc"
.include "hardware.inc"
entry:
jsr reset
jsr make_tables
; CODE[0]=1 -> transform and draw
; CODE[1]=1 -> transform and draw
lda #1
sta CODE_arr
sta CODE_arr+1
; X[0]=127 Y[0]=96:X[1]=20:Y[1]=30 -> co-ord of center
; SCALE[0]=15:XROT[0]=2:YROT[0]=5:ZROT[0]=0
; SCALE[1]=15:XROT[1]=2:YROT[1]=5:ZROT[1]=0
jsr CRUNCH
jsr CRUNCH
; CODE[0]=2:CODE[1]=2 -> erase and draw new
lda #2
sta CODE_arr
sta CODE_arr+1
loop:
; ZROT[0]+=1: IF ZEROT[0]==28 THEN ZROT[0]=0
; YROT[1]=ZROT[0]
inc ZROT_arr
lda ZROT_arr
cmp #28
bne zrot_ok
lda #0
sta ZROT_arr
zrot_ok:
sta YROT_arr+1
jsr CRUNCH
jmp loop
;===========================================================
; Note that all tables are page-aligned for performance. *
;===========================================================
.include "shapes.s"
.align $100
.include "math_constants.s"
.include "scale_constants.s"
make_tables:
; Make hires row lookup table using HPOSN
; From the Applesoft ROM
ldx #0
hgr_table_loop:
ldy #0
txa
jsr HPOSN ; (Y,X),(A) (values stores in HGRX,XH,Y)
ldx HGR_X
lda GBASL
sta YTableLo,X
lda GBASH
sta YTableHi,X
inx
cpx #192
bne hgr_table_loop
;=====================
; Make Div7 table
lda #0
tax
tay
div7_table_loop:
sta Div7Tab,X
iny
cpy #7
bne not_7
ldy #0
clc
adc #1
not_7:
inx
bne div7_table_loop
;
; Hi-res bit table. Converts the X coordinate (0-255) into a bit position
; within a byte. (Essentially 2 to the power of the remainder of the coordinate
; divided by 7.)
;
lda #1
ldx #0
ldy #0
bittab_table_loop:
sta HiResBitTab,X
asl
iny
cpy #7
bne again_not_7
ldy #0
lda #1
again_not_7:
inx
bne bittab_table_loop
rts
;====================================
; DrawLineList
;====================================
DrawLineList:
;
; Draw a list of lines using exclusive-or, which inverts the pixels. Drawing
; the same thing twice erases it.
;
; On entry:
; $45 - index of first line
; $46 - index of last line
; XCoord_0E/YCoord_0F or XCoord_10/YCoord_11 have transformed points in screen
; coordinates
;
; When the module is configured for OR-mode drawing, this code is replaced with
; a dedicated erase function. The erase code is nearly identical to the draw
; code, but saves a little time by simply zeroing out whole bytes instead of
; doing a read-modify-write.
;
; Draw code calls here. Since we're configured for XOR mode,
; this just jumps to the exclusive-or version.
DrawLineListEOR:
ldx FIRST_LINE ; 3 start with the first line in this object
DrawLoop:
lda LineStartPoint,X; 4+ get X0,Y0
tay ; 2
_0E_or_10_1:
lda XCoord0_0E,Y ; 4+ the instructions here are modified to load from
sta XSTART ; 3 the appropriate set of X/Y coordinate tables
_0F_or_11_1:
lda YCoord0_0F,Y ; 4+
sta YSTART ; 3
lda LineEndPoint,X ; 4+ get X1,Y1
tay ; 2
_0E_or_10_2:
lda XCoord0_0E,Y ; 4+
sta XEND ; 3
_0F_or_11_2:
lda YCoord0_0F,Y ; 4+
sta YEND ; 3
stx LINE_INDEX ; 3 save this off
; Prep the line draw code. We need to compute deltaX/deltaY, and set a register
; increment / decrement / no-op instruction depending on which way the line is
; going.
lda XSTART ; 3 compute delta X
sec ; 2
sbc XEND ; 3
bcs L1A2F ; 2+ left to right
eor #$ff ; 2 right to left; invert value
adc #$01 ; 2
ldy #OpINX ; 2
bne GotDeltaX ; 3
L1A2F:
beq IsVertical ; 2+ branch if deltaX=0
ldy #OpDEX ; 2
bne GotDeltaX ; 3
IsVertical:
ldy #OpNOP ; 2 fully vertical, use no-op
GotDeltaX:
sta DELTA_X ; 3
sty _InxDexNop1 ; 4
sty _InxDexNop2 ; 4
lda YSTART ; 3 compute delta Y
sec ; 2
sbc YEND ; 3
bcs L1A4E ; 2+ end < start, we're good
eor #$ff ; 2 invert value
adc #$01 ; 2
ldy #OpINY ; 2
bne GotDeltaY ; 3
L1A4E:
beq IsHorizontal ; 2+ branch if deltaY=0
ldy #OpDEY ; 2
bne GotDeltaY ; 3
IsHorizontal:
ldy #OpNOP ; 2 fully horizontal, use no-op
GotDeltaY:
sta DELTA_Y ; 3
sty _InyDeyNop1 ; 4
sty _InyDeyNop2 ; 4
ldx XSTART ; 3
ldy YSTART ; 3
lda #$00 ; 2
sta LINE_ADJ ; 3
lda DELTA_X ; 3
cmp DELTA_Y ; 3
bcs HorizDomLine ; 2+
; Line draw: vertically dominant (move vertically every step)
;
; On entry: X=xpos, Y=ypos
VertDomLine:
cpy YEND ; 3
beq LineDone ; 2+
_InyDeyNop1:
nop ; 2 self-mod INY/DEY/NOP
lda YTableLo,Y ; 4+ new line, update Y position
sta HPTR ; 3
lda YTableHi,Y ; 4+
ora HPAGE ; 3
sta HPTR+1 ; 3
lda LINE_ADJ ; 3 Bresenham update
clc ; 2
adc DELTA_X ; 3
cmp DELTA_Y ; 3
bcs NewColumn ; 2+
sta LINE_ADJ ; 3
bcc SameColumn ; 3
NewColumn:
sbc DELTA_Y ; 3
sta LINE_ADJ ; 3
_InxDexNop1:
nop ;2 self-mod INX/DEX/NOP
SameColumn:
sty YSAVE ; 3
ldy Div7Tab,X ; 4+ XOR-draw the point
lda (HPTR),Y ; 5+
eor HiResBitTab,X ; 4+
sta (HPTR),Y ; 6
ldy YSAVE ; 3
jmp VertDomLine ; 3
LineDone:
ldx LINE_INDEX ; 3
inx ; 2
cpx LAST_LINE ; 3 reached end?
beq DrawDone ; 2+
jmp DrawLoop ; 3
DrawDone:
rts ; 6
; Line draw: horizontally dominant (move horizontally every step)
;
; On entry: X=xpos, Y=ypos
HorizDomLine:
lda YTableLo,Y ; 4+ set up hi-res pointer
sta HPTR ; 3
lda YTableHi,Y ; 4+
ora HPAGE ; 3
sta HPTR+1 ; 3
HorzLoop:
cpx XEND ; 3 X at end?
beq LineDone ; 2+ yes, finish
_InxDexNop2:
nop ; 2
lda LINE_ADJ ; 3 Bresenham update
clc ; 2
adc DELTA_Y ; 3
cmp DELTA_X ; 3
bcs NewRow ; 2+
sta LINE_ADJ ; 3
bcc SameRow ; 3
NewRow:
sbc DELTA_X ; 3
sta LINE_ADJ ; 3
_InyDeyNop2:
nop ; 2
lda YTableLo,Y ; 4+ update Y position
sta HPTR ; 3
lda YTableHi,Y ; 4+
ora HPAGE ; 3
sta HPTR+1 ; 3
SameRow:
sty YSAVE ; 3
ldy Div7Tab,X ; 4+ XOR-draw the point
lda (HPTR),Y ; 5+
eor HiResBitTab,X ; 4+
sta (HPTR),Y ; 6
ldy YSAVE ; 3
jmp HorzLoop ; 3
; Current hi-res page.
;
; $00 = draw page 1, show page 2
; $FF = draw page 2, show page 1
CurPage: .byte $ff
;
; Switch to the other hi-res page.
;
SwapPage:
lda CurPage ; 4
eor #$ff ; 2 flip to other page
sta CurPage ; 4
beq DrawOnPage1 ; 3+
sta TXTPAGE1 ; 4 draw on page 2, show page 1
lda #$40 ; 2
ldx #>XCoord1_10 ; 2
ldy #>YCoord1_11 ; 2
bne L1C0F ; 3
DrawOnPage1:
sta TXTPAGE2 ; 4 draw on page 1, show page 2
lda #$20 ; 2
ldx #>XCoord0_0E ; 2
ldy #>YCoord0_0F ; 2
; Save the hi-res page, and modify the instructions that read from or write data
; to the transformed point arrays.
L1C0F:
sta HPAGE ; 3
stx _0E_or_10_1+2 ; 4
stx _0E_or_10_2+2 ; 4
stx _0E_or_10_3+2 ; 4
sty _0F_or_11_1+2 ; 4
sty _0F_or_11_2+2 ; 4
sty _0F_or_11_3+2 ; 4
rts ; 6
; Coordinate transformation function. Transforms all points in a single object.
;
; On entry:
; 1c = SCALE (00-0f)
; 1d = XC (00-ff)
; 1e = YC (00-bf)
; 1f = ZROT (00-1b)
; 3c = YROT (00-1b)
; 3d = XROT (00-1b)
; 45 = index of first point to transform
; 46 = index of last point to transform
;
; Rotation values greater than $1B, and scale factors greater than $0F, disable
; the calculation. This has the same effect as a rotation value of 0 or a scale
; of 15, but is more efficient, because this uses self-modifying code to skip
; the computation entirely.
;
CompTransform:
ldx FIRST_POINT ; 3 get first point index; this stays in X for a while
; Configure Z rotation.
ldy ZROT ; 3
cpy #$1c ; 2 valid rotation value?
bcc ConfigZrot ; 2+ yes, configure
lda #<DoYrot ; 2 no, modify code to skip Z-rot
sta _BeforeZrot+1 ; 4
bne NoZrot ; 3
ConfigZrot:
lda #<DoZrot ; 2
sta _BeforeZrot+1 ; 4
lda RotIndexLo_sin,Y ; 4+
sta _zrotLS1+1 ; 4
sta _zrotLS2+1 ; 4
lda RotIndexHi_sin,Y ; 4+
sta _zrotHS1+1 ; 4
sta _zrotHS2+1 ; 4
lda RotIndexLo_cos,Y ; 4+
sta _zrotLC1+1 ; 4
sta _zrotLC2+1 ; 4
lda RotIndexHi_cos,Y ; 4+
sta _zrotHC1+1 ; 4
sta _zrotHC2+1 ; 4
; Configure Y rotation.
NoZrot:
ldy YROT ; 3
cpy #$1c ; 2 valid rotation value?
bcc ConfigYrot ; 2+ yes, configure
lda #<DoXrot ; 2 no, modify code to skip Y-rot
sta _BeforeYrot+1 ; 4
bne NoYrot ; 3
ConfigYrot:
lda #<DoYrot ; 2
sta _BeforeYrot+1 ; 4
lda RotIndexLo_sin,Y ; 4+
sta _yrotLS1+1 ; 4
sta _yrotLS2+1 ; 4
lda RotIndexHi_sin,Y ; 4+
sta _yrotHS1+1 ; 4
sta _yrotHS2+1 ; 4
lda RotIndexLo_cos,Y ; 4+
sta _yrotLC1+1 ; 4
sta _yrotLC2+1 ; 4
lda RotIndexHi_cos,Y ; 4+
sta _yrotHC1+1 ; 4
sta _yrotHC2+1 ; 4
; Configure X rotation.
NoYrot:
ldy XROT ; 3
cpy #$1c ; 2 valid rotation value?
bcc ConfigXrot ; 2+ yes, configure
lda #<DoScale ; 2 no, modify code to skip X-rot
sta _BeforeXrot+1 ; 4
bne ConfigScale ; 3
ConfigXrot:
lda #<DoXrot ; 2
sta _BeforeXrot+1 ; 4
lda RotIndexLo_sin,Y ; 4+
sta _xrotLS1+1 ; 4
sta _xrotLS2+1 ; 4
lda RotIndexHi_sin,Y ; 4+
sta _xrotHS1+1 ; 4
sta _xrotHS2+1 ; 4
lda RotIndexLo_cos,Y ; 4+
sta _xrotLC1+1 ; 4
sta _xrotLC2+1 ; 4
lda RotIndexHi_cos,Y ; 4+
sta _xrotHC1+1 ; 4
sta _xrotHC2+1 ; 4
; Configure scaling.
ConfigScale:
ldy SCALE ; 3
cpy #$10 ; 2 valid SCALE value?
bcc SetScale ; 2+ yes, configure it
lda #<DoTranslate ; 2 no, skip it
sta _BeforeScale+1 ; 4
lda #>DoTranslate ; 2
sta _BeforeScale+2 ; 4
bne TransformLoop ; 4
SetScale:
lda #<DoScale ; 2
sta _BeforeScale+1 ; 4
lda #>DoScale ; 2
sta _BeforeScale+2 ; 4
lda ScaleIndexLo,Y ; 4+ $00, $10, $20, ... $F0
sta _scaleLX+1 ; 4
sta _scaleLY+1 ; 4
lda ScaleIndexHi,Y ; 4+ $00, $01, $02, ... $0F
sta _scaleHX+1 ; 4
sta _scaleHY+1 ; 4
;
; Now that we've got the code modified, perform the computation for all points
; in the object.
;
TransformLoop:
lda ShapeXCoords,X ; 4+
sta XC ; 3
lda ShapeYCoords,X ; 4+
sta YC ; 3
lda ShapeZCoords,X ; 4+
sta ZC ; 3
stx OUT_INDEX ; 3 save for later
_BeforeZrot:
jmp DoZrot ; 3
DoZrot:
lda XC ; 3 rotating about Z, so we need to update X/Y coords
and #$0f ; 2 split X/Y into nibbles
sta ROT_TMP ; 3
lda XC ; 3
and #$f0 ; 2
sta ROT_TMP+1 ; 3
lda YC ; 3
and #$0f ; 2
sta ROT_TMP+2 ; 3
lda YC ; 3
and #$f0 ; 2
sta ROT_TMP+3 ; 3
ldy ROT_TMP ; 3 transform X coord
ldx ROT_TMP+1 ; 3 XC = X * cos(theta) - Y * sin(theta)
_zrotLC1:
lda RotTabLo,Y ; 4+
clc ; 2
_zrotHC1:
adc RotTabHi,X ; 4+
ldy ROT_TMP+2 ; 3
ldx ROT_TMP+3 ; 3
sec ; 2
_zrotLS1:
sbc RotTabLo,Y ; 4+
sec ; 2
_zrotHS1:
sbc RotTabHi,X ; 4+
sta XC ; 3 save updated coord
_zrotLC2:
lda RotTabLo,Y ; 4+ transform Y coord
clc ; 2 YC = Y * cos(theta) + X * sin(theta)
_zrotHC2:
adc RotTabHi,X ; 4+
ldy ROT_TMP ; 3
ldx ROT_TMP+1 ; 3
clc ; 2
_zrotLS2:
adc RotTabLo,Y ; 4+
clc ; 2
_zrotHS2:
adc RotTabHi,X ; 4+
sta YC ; 3 save updated coord
_BeforeYrot:
jmp DoYrot ; 3
DoYrot:
lda XC ; 3 rotating about Y, so update X/Z
and #$0f ; 2
sta ROT_TMP ; 3
lda XC ; 3
and #$f0 ; 2
sta ROT_TMP+1 ; 3
lda ZC ; 3
and #$0f ; 2
sta ROT_TMP+2 ; 3
lda ZC ; 3
and #$f0 ; 2
sta ROT_TMP+3 ; 3
ldy ROT_TMP ; 3
ldx ROT_TMP+1 ; 3
_yrotLC1:
lda RotTabLo,Y ; 4+
clc ; 2
_yrotHC1:
adc RotTabHi,X ; 4+
ldy ROT_TMP+2 ; 3
ldx ROT_TMP+3 ; 3
sec ; 2
_yrotLS1:
sbc RotTabLo,Y ; 4+
sec ; 2
_yrotHS1:
sbc RotTabHi,X ; 4+
sta XC ; 3
_yrotLC2:
lda RotTabLo,Y ; 4+
clc ; 2
_yrotHC2:
adc RotTabHi,X ; 4+
ldy ROT_TMP ; 3
ldx ROT_TMP+1 ; 3
clc ; 2
_yrotLS2:
adc RotTabLo,Y ; 4+
clc ; 2
_yrotHS2:
adc RotTabHi,X ; 4+
sta ZC ; 3
_BeforeXrot:
jmp DoXrot ; 3
DoXrot:
lda ZC ; 3 rotating about X, so update Z/Y
and #$0f ; 2
sta ROT_TMP ; 3
lda ZC ; 3
and #$f0 ; 2
sta ROT_TMP+1 ; 3
lda YC ; 3
and #$0f ; 2
sta ROT_TMP+2 ; 3
lda YC ; 3
and #$f0 ; 2
sta ROT_TMP+3 ; 3
ldy ROT_TMP ; 3
ldx ROT_TMP+1 ; 3
_xrotLC1:
lda RotTabLo,Y ; 4+
clc ; 2
_xrotHC1:
adc RotTabHi,X ; 4+
ldy ROT_TMP+2 ; 3
ldx ROT_TMP+3 ; 3
sec ; 2
_xrotLS1:
sbc RotTabLo,Y ; 4+
sec ; 2
_xrotHS1:
sbc RotTabHi,X ; 4+
sta ZC ; 3
_xrotLC2:
lda RotTabLo,Y ; 4+
clc ; 2
_xrotHC2:
adc RotTabHi,X ; 4+
ldy ROT_TMP ; 3
ldx ROT_TMP+1 ; 3
clc ; 2
_xrotLS2:
adc RotTabLo,Y ; 4+
clc ; 2
_xrotHS2:
adc RotTabHi,X ; 4+
sta YC ; 3
_BeforeScale:
jmp DoScale ; 3
; Apply scaling. Traditionally this is applied before rotation.
DoScale:
lda XC ; 3 scale the X coordinate
and #$f0 ; 2
tax ; 2
lda XC ; 3
and #$0f ; 2
tay ; 2
_scaleLX:
lda ScaleTabLo,Y ; 4+
clc ; 2
_scaleHX:
adc ScaleTabHi,X ; 4+
sta XC ; 3
lda YC ; 3 scale the Y coordinate
and #$f0 ; 2
tax ; 2
lda YC ; 3
and #$0f ; 2
tay ; 2
_scaleLY:
lda ScaleTabLo,Y ; 4+
clc ; 2
_scaleHY:
adc ScaleTabHi,X ; 4+
sta YC ; 3
;
; Apply translation.
;
; This is the final step, so the result is written to the transformed-point
; arrays.
;
DoTranslate:
ldx OUT_INDEX ; 3
lda XC ; 3
clc ; 2
adc XPOSN ; 3 object center in screen coordinates
_0E_or_10_3:
sta XCoord0_0E,X ; 5
lda YPOSN ; 3
sec ; 2
sbc YC ; 3
_0F_or_11_3:
sta YCoord0_0F,X ; 5
inx ; 2
cpx LAST_POINT ; 3 done?
beq TransformDone ; 2+ yes, bail
jmp TransformLoop ; 3
TransformDone:
rts ; 6
SavedShapeIndex:
.byte $ad ;holds shape index while we work
;*******************************************************************************
; CRUNCH/CRNCH% entry point *
; *
; For each object, do what CODE%(n) tells us to: *
; *
; 0 - do nothing *
; 1 - transform and draw *
; 2 - erase, transform, draw *
; 3 - erase *
;*******************************************************************************
CRUNCH:
;==============================
; First pass: erase old shapes
;==============================
ldx #NumObjects ; 2 number of defined objects
ShapeLoop:
dex ; 2
bmi Transform ; 2+ done
_codeAR1:
lda CODE_arr,X ; 4+
cmp #$02 ; 2 2 or 3?
bcc ShapeLoop ; 2+ no, move on
stx SavedShapeIndex ; 4
lda FirstLineIndex,X; 4+
sta FIRST_LINE ; 3
lda LastLineIndex,X ; 4+
sta LAST_LINE ; 3
cmp FIRST_LINE ; 3 is number of lines <= 0?
bcc NoLines1 ; 2+
beq NoLines1 ; 2+ yes, skip draw
jsr DrawLineListEOR ; 6 erase with EOR version, regardless of config
NoLines1:
ldx SavedShapeIndex ; 4
jmp ShapeLoop ; 3 ...always
;===============================
; Second pass: transform shapes
;===============================
Transform:
ldx #NumObjects ; 2
TransLoop:
dex ; 2
bmi DrawNew ; 2+
_codeAR2:
lda CODE_arr,X ; 4+
beq TransLoop ; 2+ is it zero or three?
cmp #$03 ; 2
beq TransLoop ; 2+ yes, we only draw on 1 or 2
; Extract the scale, X/Y, and rotation values out of the arrays and copy them to
; zero-page locations.
_scaleAR:
lda SCALE_arr,X ; 4+
sta SCALE ; 3
_xAR:
lda X_arr,X ; 4+
sta XPOSN ; 3
_yAR:
lda Y_arr,X ; 4+
sta YPOSN ; 3
_zrotAR:
lda ZROT_arr,X ; 4+
sta ZROT ; 3
_yrotAR:
lda YROT_arr,X ; 4+
sta YROT ; 3
_xrotAR:
lda XROT_arr,X ; 4+
sta XROT ; 3
stx SavedShapeIndex ; 4 save this off
lda FirstPointIndex,X; 4+
sta FIRST_LINE ; 3 (actually first_point)
lda LastPointIndex,X; 4+
sta LAST_LINE ; 3
cmp FIRST_LINE ; 3 is number of points <= 0?
bcc NoPoints ; 2+
beq NoPoints ; 2+ yes, skip transform
jsr CompTransform ; 6 transform all points
NoPoints:
ldx SavedShapeIndex ; 4
lda XC ; 3
clc ; 2
adc XPOSN ; 3
_sxAR:
sta SX_arr,X ; 5
lda YPOSN ; 3
sec ; 2
sbc YC ; 3
_syAR:
sta SY_arr,X ; 5
jmp TransLoop ; 3
;=============================
; Third pass: draw shapes
;=============================
DrawNew:
ldx #NumObjects ; 2
L1ECE:
dex ; 2
bmi L1EF9 ; 2+
_codeAR3:
lda CODE_arr,X ; 4+ is it 0 or 3?
beq L1ECE ; 2+
cmp #$03 ; 2
beq L1ECE ; 2+ yup, no draw
stx SavedShapeIndex ; 4 save index
lda FirstLineIndex,X; 4+ draw all the lines in the shape
sta FIRST_LINE ; 3
lda LastLineIndex,X ; 4+
sta LAST_LINE ; 3
cmp FIRST_LINE ; 3 is number of lines <= 0?
bcc NoLines2 ; 2+
beq NoLines2 ; 2+ yes, skip draw
jsr DrawLineList ; 6 draw all lines
NoLines2:
ldx SavedShapeIndex ; 4
bpl L1ECE ; 3 ...always
L1EF9:
jmp SwapPage ; 3
;===============================================
;===============================================
; RESET entry point
;
; + Zeroes out the CODE array
; + erases both hi-res screens
; + enables display of the primary hi-res page
;===============================================
;===============================================
reset:
; lda #$0
; ldy #$F
;zero_code_loop:
; sta CODE_arr,y ; 5 zero out CODE
; dey ; 2
; bpl zero_code_loop ; 3+
jsr CLEAR ; 6
jsr SwapPage ; 6
jsr SwapPage ; 6
rts ; 6
;*******************************************************************************
; CLEAR/CLR% entry point *
; *
; Clears both hi-res pages. *
;*******************************************************************************
; Clear variables
CLEAR:
lda #$20 ; 2 hi-res page 1
sta PTR1+1 ; 3
lda #$40 ; 2 hi-res page 2
sta PTR2+1 ; 3
ldy #$00 ; 2
sty PTR1 ; 3
sty PTR2 ; 3
L1F1D:
tya ; 2
L1F1E:
sta (PTR1),Y ; 6 erase both pages
sta (PTR2),Y ; 6
iny ; 2
bne L1F1E ; 2+
inc PTR1+1 ; 5
inc PTR2+1 ; 5
lda PTR1+1 ; 3 (could hold counter in X-reg)
and #$3f ; 2
bne L1F1D ; 2+
;==============================
; HIRES entry point
;
; Displays primary hi-res page.
;===============================
hi_res:
sta HIRES ; 4
sta MIXCLR ; 4
sta TXTCLR ; 4
rts ; 6
; size these as appropriate
; we are assuming only 2 shapes here, can be up to 16
CODE_arr:
.byte $00,$00
X_arr:
.byte 127,20
Y_arr:
.byte 96,30
XROT_arr:
.byte 2,2
YROT_arr:
.byte 5,5
ZROT_arr:
.byte 0,0
SCALE_arr:
.byte 15,15
SX_arr:
.byte $00,$00
SY_arr:
.byte $00,$00
; layout:
;
; These four buffers hold transformed points in screen coordinates. The points
; are in the same order as they are in the mesh definition.
;
; One pair of tables holds the X/Y screen coordinates from the previous frame,
; the other pair of tables holds the coordinates being transformed for the
; current frame. We need two sets because we're display set 0 while generating
; set 1, and after we flip we need to use set 0 again to erase the display.
;
; ----------
;
; Computed X coordinate, set 0.
XCoord0_0E = $6000
; Computed Y coordinate, set 0.
YCoord0_0F = $6100
; Computed X coordinate, set 1.
XCoord1_10 = $6200
; Computed Y coordinate, set 1.
YCoord1_11 = $6300
; hgr lookup
YTableLo = $6400
YTableHi = $6500
Div7Tab = $6600
HiResBitTab = $6700
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