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Couple people asked about how I did sprite rotation for josefnpat's collab cart https://www.lexaloffle.com/bbs/?tid=27582
Included is a sprite rotation function, and a way of layering them on top of each other to create an illusion of a 3d sprite.
Everything is commented, hopefully it's clear.
Enjoy, hope this is helpful for someone!

Cart #28035 | 2016-09-05 | Code ▽ | Embed ▽ | License: CC4-BY-NC-SA
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(the effect isn't perfect and can be a little unclear if you don't consider it when drawing sprites, if anyone has any more accurate examples of rotation functions I'd like to see!)

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Very cool effect. Thanks!

neat! and as good as you can get imho.

tried optimizing/rewriting rotsprite, stat(1) went from 0.36 to 0.30 on your cart:

 
function rotsprite(sprite, posx, posy, angle)
	local scx = sprite%16*8
	local scy = flr(sprite/16)*8
	local cs = cos(angle)
	local sn = sin(angle)
	local cpx=-5*(cs-sn) +4
	local cpy=-5*(sn+cs) +4
	for x=-5,5 do
		local px=cpx
		local py=cpy
		for y=-5,5 do
			if (px>=0 and px<8 and py>=0 and py<8) then
				local col = sget(scx+px, scy+py)
				if (col ~= 0) pset(posx+x, posy+y, col)
			end
			px-=sn
			py+=cs
		end
		cpx+=cs
		cpy+=sn
	end
end



Oh, good to see, cheers!

just found out I had this optimized further but didn't update here:

 
function layeredsprite(sprite, posx, posy, angle, layers)
	local cs,sn = cos(angle),sin(angle)
	local osx,osy = -5*(cs-sn)+4,-5*(sn+cs)+4
	local spx,spy = 8*(sprite%16),8*flr(sprite/16)
	for layer=1, layers do
		local csx,csy = osx,osy
		for x=-5,5 do
			local sx,sy = csx,csy
			for y=-5,5 do
				if (sx>=0 and sx<8 and sy>=0 and sy<8) then
					local col = sget(spx+sx, spy+sy)
					if (col~=0) pset(posx+x, posy+y, col)
				end
				sx-=sn sy+=cs
			end
			csx+=cs csy+=sn
		end
		spx+=8 --layers on same row pls
		posy-=1
	end
end

merged rotsprite() in layeredsprite(), demo runs at 0.24

Is there a way to zoom these sprites, UB ?

not out of the box dw, also this works on single sprites (8x8).
sizes are hardcoded, but should be 'easily' adapted.
if somebody needs help about that, I can have a look, but I won't right now ;)



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