Shader - Circle and Rectangle functions

gistfile1.glsl

// returns 1.0 if inside circle
float disk(vec2 r, vec2 center, float radius) {
	return 1.0 - smoothstep( radius-0.005, radius+0.005, length(r-center));
}
// returns 1.0 if inside the disk
float rectangle(vec2 r, vec2 bottomLeft, vec2 topRight) {
	float ret;
	float d = 0.005;
	ret = smoothstep(bottomLeft.x-d, bottomLeft.x+d, r.x);
	ret *= smoothstep(bottomLeft.y-d, bottomLeft.y+d, r.y);
	ret *= 1.0 - smoothstep(topRight.y-d, topRight.y+d, r.y);
	ret *= 1.0 - smoothstep(topRight.x-d, topRight.x+d, r.x);
	return ret;
}