triangles.lua

require "gd"

size = 400

im = gd.createPalette(size, size)
assert(im)

black = im:colorAllocate(0, 0, 0)
im:gifAnimBegin("out.gif", true, 0)

r = 40
steps = 60
angle = 2*math.pi/steps
for i = 1, steps*2 do
    --tim = gd.create(size, size)
    --tim:paletteCopy(im)
    tim = gd.createTrueColor(size, size)
    --tim:arc(40, 40, 40, 40, 36*(i-1), 36*i, white)
    angles = {{
        angle*i,
        angle*i+2*math.pi/3,
        angle*i+4*math.pi/3,
        -angle*i+2*math.pi,
        -angle*i+4*math.pi/3,
        -angle*i+2*math.pi/3},{
        angle*i+math.pi,
        angle*i+2*math.pi/3+math.pi,
        angle*i+4*math.pi/3+math.pi,
        -angle*i+2*math.pi+math.pi,
        -angle*i+4*math.pi/3+math.pi,
        -angle*i+2*math.pi/3+math.pi}}
    table.sort(angles[1])
    table.sort(angles[2])
    for cx = -8, 12 do
        c = cx%2+1
        oy = cx%2
        for cy = -5, 9, 2 do
            points = {}
            for a = 1, #angles[c] do
                table.insert(points, {
                    r*(cx+math.cos(angles[c][a]))+oy*i*2,
                    r*(cy+math.sin(angles[c][a]))+oy*i*2})
            end
            w = 255-math.sqrt(math.pow(r*cx+oy*i*2-size/2, 2)+math.pow(r*cy+oy*i*2-size/2, 2))/2
            if w > 0 then
                tim:filledPolygon(points, tim:colorAllocate(w, w, w))
            end
            --tim:polygon(points, white)
        end
    end
    ti = tim:createPaletteFromTrueColor(true, 5)
    ti:gifAnimAdd("out.gif", true, 0, 0, 5, gd.DISPOSAL_NONE)
end

gd.gifAnimEnd("out.gif")

print("Gif animation written to 'out.gif' file")