arcprogressbar.lua

function CreateHollowCircle(x, y, innerRadius, outerRadius, startAngle, rotation)
    rotation = math.min(rotation or (math.pi * 2), math.pi * 2)
    startAngle = startAngle or 0
    local quality = math.min(256, 4 * math.sqrt(outerRadius) + 8)
    local verts = {}
    local angA, angB
    local mul = math.pi * 2 / quality
    local count = quality * rotation / (math.pi * 2)
    for i = 0, count do
        angA = startAngle + i * mul
        angB = angA + mul
        if angB - startAngle > rotation then angB = startAngle + rotation end
        sinA, cosA = sin(angA), cos(angA)
        sinB, cosB = sin(angB), cos(angB)
        verts[i + 1] = {
            { x = x + cosA * innerRadius, y = y + sinA * innerRadius },
            { x = x + cosA * outerRadius, y = y + sinA * outerRadius },
            { x = x + cosB * outerRadius, y = y + sinB * outerRadius },
            { x = x + cosB * innerRadius, y = y + sinB * innerRadius }
        }
    end
    return verts
end