Apple-2-SW/prog8
1
0
Fork 0
mirror of https://github.com/irmen/prog8.git synced 2025-01-13 10:29:52 +00:00
Code Issues Projects Releases Wiki Activity

fix cx16 bresenham line inaccuracy

Browse Source
This commit is contained in:
Irmen de Jong 2021-03-09 21:54:31 +01:00
parent 6c60ea9cac
commit 6995ee2d17
3 changed files with 27 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
compiler/res/prog8lib/cx16/gfx2.p8
View File

@ -433,7 +433,6 @@ _done
sub line(uword @zp x1, uword @zp y1, uword @zp x2, uword @zp y2, ubyte color) {
; Bresenham algorithm.
; This code special-cases various quadrant loops to allow simple ++ and -- operations.
; TODO there are some slight errors at the first/last pixels in certain slopes...
if y1>y2 {
; make sure dy is always positive to have only 4 instead of 8 special cases
swap(x1, x2)
@ -455,26 +454,26 @@ _done
; TODO rewrite the rest in optimized assembly (or reuse GRAPH_draw_line if we can get the FB replacement vector layer working)
word @zp d = 0
ubyte positive_ix = true
cx16.r13 = true ; 'positive_ix'
if dx < 0 {
dx = -dx
positive_ix = false
cx16.r13 = false
}
dx *= 2
dy *= 2
word @zp dx2 = dx*2
word @zp dy2 = dy*2
cx16.r14 = x1 ; internal plot X
if dx >= dy {
if positive_ix {
if cx16.r13 {
repeat {
plot(cx16.r14, y1, color)
if cx16.r14==x2
return
cx16.r14++
d += dy
d += dy2
if d > dx {
y1++
d -= dx
d -= dx2
}
}
} else {
@ -483,25 +482,25 @@ _done
if cx16.r14==x2
return
cx16.r14--
d += dy
d += dy2
if d > dx {
y1++
d -= dx
d -= dx2
}
}
}
}
else {
if positive_ix {
if cx16.r13 {
repeat {
plot(cx16.r14, y1, color)
if y1 == y2
return
y1++
d += dx
d += dx2
if d > dy {
cx16.r14++
d -= dy
d -= dy2
}
}
} else {
@ -510,10 +509,10 @@ _done
if y1 == y2
return
y1++
d += dx
d += dx2
if d > dy {
cx16.r14--
d -= dy
d -= dy2
}
}
}

2
compiler/test/UnitTests.kt
View File

@ -191,7 +191,7 @@ class TestC64Zeropage {
val zp1 = C64Zeropage(CompilationOptions(OutputType.RAW, LauncherType.NONE, ZeropageType.BASICSAFE, emptyList(), true, false, C64Target))
assertEquals(18, zp1.available())
val zp2 = C64Zeropage(CompilationOptions(OutputType.RAW, LauncherType.NONE, ZeropageType.FLOATSAFE, emptyList(), false, false, C64Target))
assertEquals(89, zp2.available())
assertEquals(85, zp2.available())
val zp3 = C64Zeropage(CompilationOptions(OutputType.RAW, LauncherType.NONE, ZeropageType.KERNALSAFE, emptyList(), false, false, C64Target))
assertEquals(125, zp3.available())
val zp4 = C64Zeropage(CompilationOptions(OutputType.RAW, LauncherType.NONE, ZeropageType.FULL, emptyList(), false, false, C64Target))

25
examples/test.p8
View File

@ -1,32 +1,31 @@
%target c64
%import floats
%import graphics
%import gfx2
%import test_stack
%zeropage floatsafe
main {
sub start() {
graphics.enable_bitmap_mode()
gfx2.screen_mode(1)
;graphics.enable_bitmap_mode()
uword xx
ubyte yy
graphics.line(160,100,160,80)
graphics.line(160,80,180,81)
graphics.line(180,81,177,103)
gfx2.line(160,100,160,80 ,1)
gfx2.line(160,80,180,81 ,1)
gfx2.line(180,81,177,103 ,1)
for yy in 0 to 199-60 step 16 {
for xx in 0 to 319-50 step 16 {
graphics.line(30+xx, 10+yy, 50+xx, 30+yy)
graphics.line(49+xx, 30+yy, 10+xx, 30+yy)
graphics.line(11+xx, 29+yy, 29+xx, 11+yy)
gfx2.line(30+xx, 10+yy, 50+xx, 30+yy ,1)
gfx2.line(49+xx, 30+yy, 10+xx, 30+yy ,1)
gfx2.line(11+xx, 29+yy, 29+xx, 11+yy ,1)
; triangle 2, counter-clockwise
graphics.line(30+xx, 40+yy, 10+xx, 60+yy)
graphics.line(11+xx, 60+yy, 50+xx, 60+yy)
graphics.line(49+xx, 59+yy, 31+xx,41+yy)
gfx2.line(30+xx, 40+yy, 10+xx, 60+yy ,1)
gfx2.line(11+xx, 60+yy, 50+xx, 60+yy ,1)
gfx2.line(49+xx, 59+yy, 31+xx,41+yy ,1)
}
}