Some GLSL shader functions

functions.frag

vec3 square(vec2 st,vec2 bli,vec2 tri,vec3 color) {
    // bottom-left
    vec2 bl = step(bli,st);

    // top-right
    vec2 tr = step(1.0-tri,1.0-st);
    float pct = bl.x * bl.y * tr.x * tr.y;

    vec3 c = vec3(pct * color);

    return c;
}