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fix bresenham line
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Irmen de Jong
parent
fac2a2d7cb
commit
fffe36e358
@ -14,6 +14,12 @@ import kotlin.math.pow
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/*
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todo add more expression optimizations
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x + x -> x << 1 (for words... for bytes too?)
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x + x + x + x -> x << 2 (for words... for bytes too?)
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x + x + x -> ???? x*3 ??? words/bytes?
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x - x -> 0
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Investigate what optimizations binaryen has, also see https://egorbo.com/peephole-optimizations.html
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*/
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@ -1,77 +1,96 @@
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%import c64lib
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%import c64utils
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%zeropage basicsafe
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; bitmap pixel graphics module for the C64
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; only black/white monchrome for now
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main {
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; you could put this code at $4000 which is after the bitmap screen in memory ($2000-$3fff),
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; this leaves more space for user program code.
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graphics {
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const uword bitmap_address = $2000
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sub start() {
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sub enable_bitmap_mode() {
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; enable bitmap screen, erase it and set colors to black/white.
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c64.SCROLY |= %00100000
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c64.VMCSB = (c64.VMCSB & %11110000) | %00001000 ; $2000-$3fff
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memset(bitmap_address, 320*200/8, 0)
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c64scr.clear_screen($10, 0)
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lines()
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circles()
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forever {
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}
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c64scr.clear_screen($10, 0) ; pixel color $1 (white) backround $0 (black)
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}
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sub circles() {
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ubyte xx
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for xx in 3 to 7 {
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circle(xx*50-100, 10+xx*16, (xx+6)*4)
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disc(xx*50-100, 10+xx*16, (xx+6)*2)
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}
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}
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sub lines() {
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ubyte ix
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for ix in 1 to 15 {
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line(10, 10, ix*4, 50) ; TODO fix lines of lenghts > 128
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}
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}
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sub line(ubyte x1, ubyte y1, ubyte x2, ubyte y2) {
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sub line(uword x1, ubyte y1, uword x2, ubyte y2) {
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; Bresenham algorithm
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byte d = 0
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ubyte dx = abs(x2 - x1)
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ubyte dy = abs(y2 - y1)
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ubyte dx2 = 2 * dx
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ubyte dy2 = 2 * dy
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word ix = sgn(x2 as byte - x1 as byte)
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word iy = sgn(y2 as byte - y1 as byte)
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word dx
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word dy
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byte ix = 1
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byte iy = 1
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if x2>x1 {
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dx = x2-x1
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} else {
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ix = -1
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dx = x1-x2
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}
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if y2>y1 {
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dy = y2-y1
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} else {
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iy = -1
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dy = y1-y2
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}
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word dx2 = 2 * dx
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word dy2 = 2 * dy
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word d = 0
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plotx = x1
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if dx >= dy {
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forever {
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plot(y1)
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if plotx==x2
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return
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plotx += ix
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d += dy2
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if d > dx {
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y1 += iy
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d -= dx2
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if ix<0 {
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forever {
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graphics.plot(y1)
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if plotx==x2
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return
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plotx--
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d += dy2
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if d > dx {
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y1 += iy
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d -= dx2
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}
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}
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} else {
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forever {
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graphics.plot(y1)
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if plotx==x2
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return
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plotx++
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d += dy2
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if d > dx {
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y1 += iy
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d -= dx2
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}
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}
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}
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} else {
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forever {
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plot(y1)
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if y1 == y2
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return
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y1 += iy
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d += dx2
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if d > dy {
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plotx += ix
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d -= dy2
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if iy<0 {
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forever {
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plot(y1)
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if y1 == y2
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return
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y1--
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d += dx2
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if d > dy {
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plotx += ix as word
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d -= dy2
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}
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}
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} else {
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forever {
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plot(y1)
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if y1 == y2
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return
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y1++
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d += dx2
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if d > dy {
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plotx += ix as word
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d -= dy2
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}
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}
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}
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}
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@ -149,6 +168,13 @@ main {
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}
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; here is the non-asm code for the plot routine below:
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; sub plot_nonasm(uword px, ubyte py) {
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; ubyte[] ormask = [128, 64, 32, 16, 8, 4, 2, 1]
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; uword addr = bitmap_address + 320*(py>>3) + (py & 7) + (px & %0000000111111000)
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; @(addr) |= ormask[lsb(px) & 7]
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; }
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uword plotx ; 0..319
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asmsub plot(ubyte ploty @A) { ; plotx is 16 bits 0 to 319... doesn't fit in a register
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@ -219,13 +245,6 @@ _y_lookup_lo
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}}
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}
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; here is the non-asm code for the same plot routine:
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; sub plot_nonasm(uword px, ubyte py) {
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; ubyte[] ormask = [128, 64, 32, 16, 8, 4, 2, 1]
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; uword addr = bitmap_address + 320*(py>>3) + (py & 7) + (px & %0000000111111000)
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; @(addr) |= ormask[lsb(px) & 7]
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; }
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}
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35
examples/line-circle-gfx.p8
Normal file
35
examples/line-circle-gfx.p8
Normal file
@ -0,0 +1,35 @@
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%import c64lib
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%import c64graphics
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%zeropage basicsafe
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main {
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sub start() {
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graphics.enable_bitmap_mode()
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draw_lines()
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draw_circles()
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forever {
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}
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}
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sub draw_circles() {
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ubyte xx
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for xx in 3 to 7 {
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graphics.circle(xx*50-100, 10+xx*16, (xx+6)*4)
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graphics.disc(xx*50-100, 10+xx*16, (xx+6)*2)
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}
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}
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sub draw_lines() {
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ubyte i
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for i in 0 to 255 step 4 {
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; uword x1 = (320-256)/2 + sin8u(i)
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uword x1 = ((320-256)/2 as uword) + sin8u(i) ; TODO fix the need for a cast here
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uword y1 = (200-128)/2 + cos8u(i)/2
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uword x2 = ((320-64)/2 as uword) + sin8u(i)/4 ; TODO fix the need for a cast here
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uword y2 = (200-64)/2 + cos8u(i)/4
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graphics.line(x1, lsb(y1), x2, lsb(y2))
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}
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}
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}
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@ -64,7 +64,8 @@ main {
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}
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sub line(ubyte x1, ubyte y1, ubyte x2, ubyte y2) {
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; Bresenham algorithm
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; Bresenham algorithm, not very optimized to keep clear code.
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; For a better optimized version have a look in the graphics.p8 module.
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byte d = 0
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ubyte dx = abs(x2 - x1)
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ubyte dy = abs(y2 - y1)
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