Posted By
Mad
on 2019-12-02
11:33:32
|  Re: Assembly: fast plot and line algorithms for plus/4
If you do have a lot of memory then Grahams of Oxyron approach on painting lines probably is the fastest. But however this approach involves very much code. I do have a code generator for that somewhere. But I think a normal Bresenham like Kichy shown up there is a already pretty fast at least a lot faster than basic line drawing. Line drawing is a topic where the demoscene got pretty far already. I always feared that topic in the past.. Maybe I can dig out that code generator and give that to you later on, if Kichys algorithm isn't enough for you..
Actuall graham does this per 8x8 block as far as I remember (needs some tweaking, just as an outline of that idea):
.again
sbc ZP_SLOPE
bcc .movepixelleftandcontinue1
sbc ZP_SLOPE
bcc .movepixelleftandcontinue2
sbc ZP_SLOPE
bcc .movepixelleftandcontinue3
sbc ZP_SLOPE
bcc .movepixelleftandcontinue4
sbc ZP_SLOPE
bcc .movepixelleftandcontinue5
sbc ZP_SLOPE
bcc .movepixelleftandcontinue6
sbc ZP_SLOPE
bcc .movepixelleftandcontinue7
sbc ZP_SLOPE
bcc .movepixelleftandcontinue8
do just drawAll8YPixelsOnSameXPosition here
jmp .again
.movepixelleftandcontinue1
dec pixelXPos
drawPixel
adc ZP_SLOPEORIGIN ; this is the bigger delta (x or y) (like in bresenham)
sbc ZP_SLOPE ; this is the smaller delta (x or y) (like in bresenham)
bcc .movepixelleftandcontinue2b
sbc ZP_SLOPE
bcc .movepixelleftandcontinue3b
sbc ZP_SLOPE
bcc .movepixelleftandcontinue4b
sbc ZP_SLOPE
bcc .movepixelleftandcontinue5b
sbc ZP_SLOPE
bcc .movepixelleftandcontinue6b
sbc ZP_SLOPE
bcc .movepixelleftandcontinue7b
sbc ZP_SLOPE
bcc .movepixelleftandcontinue8b
do just drawAll7LeftYPixelsOnSameXPosition here
jmp .again
This code later gets a lot longer because of all the .movepixelleftandcontinue jumps  ..
I hope Kichys codelines up there already do the performance trick..
Good luck with your project!!!
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