Author @kynd - 2016 Title: Distance Field Shapes http://www.kynd.info

Distance Field Shapes.glsl

float circle(vec2 p, float radius) {
    return length(p) - radius;
}

float rect(vec2 p, vec2 size) {  
    vec2 d = abs(p) - size;
    return min(max(d.x, d.y), 0.0) + length(max(d, 0.0));
}

float roundRect(vec2 p, vec2 size, float radius) {
    vec2 d = abs(p) - size;
    return min(max(d.x, d.y), 0.0) + length(max(d, 0.0)) - radius;
}

float ring(vec2 p, float radius, float width) {
    return abs(length(p) - radius * 0.5) - width;
}

float hexagon(vec2 p, float radius) {
    vec2 q = abs(p);
    return max(abs(q.y), q.x * 0.866025 + q.y * 0.5) - radius;
}

float triangle(vec2 p, float size) {
    vec2 q = abs(p);
    return max(q.x * 0.866025 + p.y * 0.5, -p.y * 0.5) - size * 0.5;
}

float ellipse(vec2 p, vec2 r, float s) {
    return (length(p / r) - s);
}

float capsule(vec2 p, vec2 a, vec2 b, float r) {
    vec2 pa = p - a, ba = b - a;
    float h = clamp(dot(pa, ba) / dot(ba, ba), 0.0, 1.0 );
    return length(pa - ba * h) - r;
}

//http://thndl.com/square-shaped-shaders.html
float polygon(vec2 p, int vertices, float size) {
    float a = atan(p.x, p.y) + 0.2;
    float b = TWO_PI / float(vertices);
    return cos(floor(0.5 + a / b) * b - a) * length(p) - size;
}