dos33fsprogs/graphics/hgr/vgi-myst/vgi_triangles.s
2021-07-29 16:47:17 -04:00

97 lines
1.1 KiB
ArmAsm

; VGI Triangles
SKIP = TEMP0
;========================
; VGI vertical triangle
;========================
VGI_TCOLOR = P0
VGI_VX = P1
VGI_VY = P2
VGI_TXL = P3
VGI_TXR = P4
VGI_TYB = P5
vgi_vertical_triangle:
lda VGI_TCOLOR
lsr
lsr
lsr
lsr
sta SKIP
lda VGI_TCOLOR
and #$f
tax
lda COLORTBL,X
sta HGR_COLOR
vtri_loop:
ldy #0
ldx VGI_VX
lda VGI_VY
jsr HPLOT0 ; plot at (Y,X), (A)
ldx #0
ldy VGI_TYB
lda VGI_TXL
jsr HGLIN ; line to (X,A),(Y)
lda VGI_TXL
clc
adc SKIP
sta VGI_TXL
; inc VGI_TXL
; lda VGI_TXL
cmp VGI_TXR
bcc vtri_loop
done_vtri:
jmp vgi_loop ; bra
;========================
; VGI horizontal triangle
;========================
; VGI_TCOLOR = P0
; VGI_VX = P1
; VGI_VY = P2
VGI_THYT = P3
VGI_THYB = P4
VGI_THXR = P5
vgi_horizontal_triangle:
ldx VGI_TCOLOR
lda COLORTBL,X
sta HGR_COLOR
htri_loop:
ldy #0
ldx VGI_VX
lda VGI_VY
jsr HPLOT0 ; plot at (Y,X), (A)
ldx #0
ldy VGI_THYT
lda VGI_THXR
jsr HGLIN ; line to (X,A),(Y)
inc VGI_THYT
lda VGI_THYT
cmp VGI_THYB
bcc htri_loop
done_htri:
jmp vgi_loop