mirror of https://github.com/cc65/cc65.git
477 lines
9.6 KiB
ArmAsm
477 lines
9.6 KiB
ArmAsm
;
|
|
; Ullrich von Bassewitz, 2009-10-25
|
|
;
|
|
; Clips line coordinates to the screen coordinates and calls tgi_line
|
|
;
|
|
|
|
|
|
.import umul16x16r32, udiv32by16r16
|
|
.import negax
|
|
|
|
.include "tgi-kernel.inc"
|
|
.include "zeropage.inc"
|
|
|
|
.macpack longbranch
|
|
|
|
;----------------------------------------------------------------------------
|
|
; Data
|
|
|
|
.bss
|
|
|
|
; Outcodes for both ends
|
|
tgi_clip_o1: .res 1
|
|
tgi_clip_o2: .res 1
|
|
|
|
; Line deltas
|
|
tgi_clip_d: .res 1
|
|
tgi_clip_dx: .res 2
|
|
tgi_clip_dy: .res 2
|
|
|
|
tgi_clip_sign: .res 1
|
|
|
|
|
|
;----------------------------------------------------------------------------
|
|
; Calculate outcodes for both ends of the line
|
|
;
|
|
|
|
.code
|
|
.proc outcode1
|
|
|
|
ldy #0
|
|
jsr tgi_outcode
|
|
sta tgi_clip_o1
|
|
rts
|
|
|
|
.endproc
|
|
|
|
.code
|
|
.proc outcode2
|
|
|
|
ldy #<(tgi_clip_y2 - tgi_clip_y1)
|
|
jsr tgi_outcode
|
|
sta tgi_clip_o2
|
|
rts
|
|
|
|
.endproc
|
|
|
|
|
|
;----------------------------------------------------------------------------
|
|
; Negate tgi_clip_dxy
|
|
;
|
|
|
|
.code
|
|
.proc negate
|
|
|
|
lda tgi_clip_dx,y
|
|
eor #$FF
|
|
clc
|
|
adc #1
|
|
sta tgi_clip_dx,y
|
|
lda tgi_clip_dx+1,y
|
|
eor #$FF
|
|
adc #$00
|
|
sta tgi_clip_dx+1,y
|
|
rts
|
|
|
|
.endproc
|
|
|
|
|
|
;----------------------------------------------------------------------------
|
|
; Calculate the absolute values of dx and dy and store the combined sign in
|
|
; tgi_clip_sign
|
|
;
|
|
|
|
.code
|
|
.proc calcdeltas
|
|
|
|
lda tgi_clip_x2
|
|
sec
|
|
sbc tgi_clip_x1
|
|
sta tgi_clip_dx
|
|
lda tgi_clip_x2+1
|
|
sbc tgi_clip_x1+1
|
|
sta tgi_clip_dx+1
|
|
sta tgi_clip_sign
|
|
bpl @L1
|
|
ldy #0
|
|
jsr negate
|
|
|
|
@L1: lda tgi_clip_y2
|
|
sec
|
|
sbc tgi_clip_y1
|
|
sta tgi_clip_dy
|
|
lda tgi_clip_y2+1
|
|
sbc tgi_clip_y1+1
|
|
sta tgi_clip_dy+1
|
|
|
|
eor tgi_clip_sign
|
|
sta tgi_clip_sign
|
|
|
|
bit tgi_clip_dy+1
|
|
bpl @L9
|
|
|
|
ldy #(tgi_clip_dy - tgi_clip_dx)
|
|
jmp negate
|
|
|
|
@L9: rts
|
|
|
|
.endproc
|
|
|
|
|
|
;----------------------------------------------------------------------------
|
|
; Helper routine. Generate the absolute value of y/a and calculate the sign
|
|
; of the final result
|
|
;
|
|
|
|
.code
|
|
.proc prepare_coord
|
|
|
|
tax ; Remember high byte
|
|
eor tgi_clip_sign
|
|
sta tmp1 ; Sign of result
|
|
tya
|
|
cpx #0 ; Check sign
|
|
bpl @L1
|
|
jsr negax
|
|
@L1: sta ptr1
|
|
stx ptr1+1
|
|
rts
|
|
|
|
.endproc
|
|
|
|
|
|
;----------------------------------------------------------------------------
|
|
; Helper routine. Move the value in eax to ptr1:ptr2
|
|
;
|
|
|
|
.code
|
|
.proc move_intermediate_result
|
|
|
|
sta ptr1
|
|
stx ptr1+1
|
|
ldy sreg
|
|
sty ptr2
|
|
ldy sreg+1
|
|
sty ptr2+1
|
|
rts
|
|
|
|
.endproc
|
|
|
|
|
|
;----------------------------------------------------------------------------
|
|
; Multiply value in y/a by dy, then divide by dx.
|
|
;
|
|
|
|
.code
|
|
.proc muldiv_dydx
|
|
|
|
; Generate the absolute value of y/a and calculate the sign of the final
|
|
; result
|
|
|
|
jsr prepare_coord
|
|
|
|
; All values are positive now (dx/dy have been made positive in calcdeltas)
|
|
; and the sign of the final result is on tmp1, so we can use unsigned
|
|
; operations and apply the final result later, after rounding.
|
|
|
|
lda tgi_clip_dy
|
|
ldx tgi_clip_dy+1 ; rhs
|
|
jsr umul16x16r32 ; Multiply
|
|
|
|
; Move the result of the multiplication into ptr1:ptr2
|
|
|
|
jsr move_intermediate_result
|
|
|
|
; Load divisor and divide
|
|
|
|
lda tgi_clip_dx
|
|
ldx tgi_clip_dx+1
|
|
jsr udiv32by16r16
|
|
|
|
; Check the sign of the final result and negate it if nessary
|
|
|
|
done: bit tmp1
|
|
jmi negax
|
|
rts
|
|
|
|
.endproc
|
|
|
|
|
|
|
|
;----------------------------------------------------------------------------
|
|
; Multiply value in y/a by dx, then divide by dy.
|
|
;
|
|
|
|
.code
|
|
.proc muldiv_dxdy
|
|
|
|
; Generate the absolute value of y/a and calculate the sign of the final
|
|
; result
|
|
|
|
jsr prepare_coord
|
|
|
|
; All values are positive now (dx/dy have been made positive in calcdeltas)
|
|
; and the sign of the final result is on tmp1, so we can use unsigned
|
|
; operations and apply the final result later, after rounding.
|
|
|
|
lda tgi_clip_dx
|
|
ldx tgi_clip_dx+1 ; rhs
|
|
jsr umul16x16r32 ; Multiply
|
|
|
|
; Move the result of the multiplication into ptr1:ptr2
|
|
|
|
jsr move_intermediate_result
|
|
|
|
; Load divisor and divide
|
|
|
|
lda tgi_clip_dy
|
|
ldx tgi_clip_dy+1
|
|
jsr udiv32by16r16
|
|
|
|
; Check the sign of the final result and negate it if nessary
|
|
|
|
jmp muldiv_dydx::done
|
|
|
|
.endproc
|
|
|
|
|
|
|
|
;----------------------------------------------------------------------------
|
|
; Clip a line using Cohen Sutherland
|
|
;
|
|
|
|
.code
|
|
.proc tgi_clippedline
|
|
|
|
; Set a flag that we have no deltas calculated
|
|
|
|
lda #0
|
|
sta tgi_clip_d
|
|
|
|
; Generate outcodes
|
|
|
|
jsr outcode1
|
|
jsr outcode2
|
|
|
|
; if ((tgi_clip_o1 | tgi_clip_o2) == 0) {
|
|
; tgi_line (x1, y1, x2, y2);
|
|
; }
|
|
|
|
Loop: lda tgi_clip_o1
|
|
ora tgi_clip_o2
|
|
bne L1
|
|
|
|
; Copy the coordinates into ptr1-4 and draw the line
|
|
|
|
ldx #7
|
|
L0: lda tgi_clip_x1,x
|
|
sta ptr1,x
|
|
dex
|
|
bpl L0
|
|
jmp tgi_line
|
|
|
|
; if ((tgi_clip_o1 & tgi_clip_o2) != 0) reject;
|
|
|
|
L1: lda tgi_clip_o1
|
|
and tgi_clip_o2
|
|
beq L2
|
|
rts ; Nothing to draw
|
|
|
|
; We must clip. If we haven't already done so, calculate dx/dy.
|
|
|
|
L2: lda tgi_clip_d ; Deltas alreay calculated?
|
|
bne HaveDeltas ; Jump if yes
|
|
inc tgi_clip_d
|
|
jsr calcdeltas
|
|
|
|
; Check if X1/Y1 needs clipping
|
|
|
|
HaveDeltas:
|
|
lda tgi_clip_o1
|
|
jeq L10
|
|
|
|
; Need to clip X1/Y1
|
|
|
|
lsr a ; Check for TGI_CLIP_LEFT
|
|
bcc L3
|
|
|
|
; tgi_clip_y1 += (0 - tgi_clip_x1) * tgi_clip_dy / tgi_clip_dx;
|
|
; tgi_clip_x1 = 0;
|
|
|
|
lda #$00
|
|
tax
|
|
beq L4
|
|
|
|
L3: lsr a ; Check for TGI_CLIP_RIGHT
|
|
bcc L5
|
|
|
|
; tgi_clip_y1 += (tgi_xmax - tgi_clip_x1) * tgi_clip_dy / tgi_clip_dx;
|
|
; tgi_clip_x1 = tgi_xmax;
|
|
|
|
lda _tgi_xmax
|
|
ldx _tgi_xmax+1
|
|
|
|
L4: tay
|
|
sec
|
|
sbc tgi_clip_x1
|
|
sty tgi_clip_x1
|
|
tay
|
|
txa
|
|
sbc tgi_clip_x1+1
|
|
stx tgi_clip_x1+1
|
|
|
|
jsr muldiv_dydx
|
|
|
|
clc
|
|
adc tgi_clip_y1
|
|
sta tgi_clip_y1
|
|
txa
|
|
adc tgi_clip_y1+1
|
|
sta tgi_clip_y1+1
|
|
|
|
;
|
|
|
|
lda tgi_clip_o1
|
|
lsr a
|
|
lsr a
|
|
L5: lsr a ; Check for TGI_CLIP_BOTTOM
|
|
bcc L6
|
|
|
|
; tgi_clip_x1 = (0 - tgi_clip_y1) * tgi_clip_dx / tgi_clip_dy;
|
|
; tgi_clip_y1 = 0;
|
|
|
|
lda #$00
|
|
tax
|
|
beq L7
|
|
|
|
L6: lsr a ; Check for TGI_CLIP_TOP
|
|
bcc L8
|
|
|
|
; tgi_clip_x1 += (tgi_ymax - tgi_clip_y1) * tgi_clip_dx / tgi_clip_dy;
|
|
; tgi_clip_y1 = ymax;
|
|
|
|
lda _tgi_ymax
|
|
ldx _tgi_ymax+1
|
|
|
|
L7: tay
|
|
sec
|
|
sbc tgi_clip_y1
|
|
sty tgi_clip_y1
|
|
tay
|
|
txa
|
|
sbc tgi_clip_y1+1
|
|
stx tgi_clip_y1+1
|
|
|
|
jsr muldiv_dxdy
|
|
|
|
clc
|
|
adc tgi_clip_x1
|
|
sta tgi_clip_x1
|
|
txa
|
|
adc tgi_clip_x1+1
|
|
sta tgi_clip_x1+1
|
|
|
|
; We need to recalculate outcode1 in this case
|
|
|
|
L8: jsr outcode1
|
|
|
|
; Check if X2/Y2 needs clipping
|
|
|
|
L10: lda tgi_clip_o2
|
|
jeq Loop
|
|
|
|
; Need to clip X2/Y2
|
|
|
|
lsr a ; Check for TGI_CLIP_LEFT
|
|
bcc L11
|
|
|
|
; tgi_clip_y2 += (0 - tgi_clip_x2) * tgi_clip_dy / tgi_clip_dx;
|
|
; tgi_clip_x2 = 0;
|
|
|
|
lda #$00
|
|
tax
|
|
beq L12
|
|
|
|
L11: lsr a ; Check for TGI_CLIP_RIGHT
|
|
bcc L13
|
|
|
|
; tgi_clip_y2 += (tgi_xmax - tgi_clip_x2) * tgi_clip_dy / tgi_clip_dx;
|
|
; tgi_clip_x2 = tgi_xmax;
|
|
|
|
lda _tgi_xmax
|
|
ldx _tgi_xmax+1
|
|
|
|
L12: tay
|
|
sec
|
|
sbc tgi_clip_x2
|
|
sty tgi_clip_x2
|
|
tay
|
|
txa
|
|
sbc tgi_clip_x2+1
|
|
stx tgi_clip_x2+1
|
|
|
|
jsr muldiv_dydx
|
|
|
|
clc
|
|
adc tgi_clip_y2
|
|
sta tgi_clip_y2
|
|
txa
|
|
adc tgi_clip_y2+1
|
|
sta tgi_clip_y2+1
|
|
|
|
;
|
|
|
|
lda tgi_clip_o2
|
|
lsr a
|
|
lsr a
|
|
L13: lsr a ; Check for TGI_CLIP_BOTTOM
|
|
bcc L14
|
|
|
|
; tgi_clip_x2 += (0 - tgi_clip_y2) * tgi_clip_dx / tgi_clip_dy;
|
|
; tgi_clip_y2 = 0;
|
|
|
|
lda #$00
|
|
tax
|
|
beq L15
|
|
|
|
L14: lsr a ; Check for TGI_CLIP_TOP
|
|
bcc L16
|
|
|
|
; tgi_clip_x2 += (tgi_ymax - tgi_clip_y2) * tgi_clip_dx / tgi_clip_dy;
|
|
; tgi_clip_y2 = tgi_ymax;
|
|
|
|
lda _tgi_ymax
|
|
ldx _tgi_ymax+1
|
|
|
|
L15: tay
|
|
sec
|
|
sbc tgi_clip_y2
|
|
sty tgi_clip_y2
|
|
tay
|
|
txa
|
|
sbc tgi_clip_y2+1
|
|
stx tgi_clip_y2+1
|
|
|
|
jsr muldiv_dxdy
|
|
|
|
clc
|
|
adc tgi_clip_x2
|
|
sta tgi_clip_x2
|
|
txa
|
|
adc tgi_clip_x2+1
|
|
sta tgi_clip_x2+1
|
|
|
|
; We need to recalculate outcode2 in this case
|
|
|
|
L16: jsr outcode2
|
|
|
|
; Try again
|
|
|
|
jmp Loop
|
|
|
|
.endproc
|
|
|
|
|
|
|
|
|