Bề mặt Goursat (Goursat's surface)

Made with sdf2stl.saej.in

full SDF code:

float sdGoursat(vec3 position, float radius) // 0 <= radius < .75
{
float p4 = dot(position * position, position * position);
float p2 = dot(position, position);
// f(x,y,z) = x^4 + y^4 + z^4 - x^2 - y^2 - z^2 + radius
float f = p4 - p2 + radius;
// ∇f(x,y,z) = {4x^3 - 2x, 4y^3 - 2y, 4z^3 - 2z}
vec3 df = 4. * position * position * position - 2. * position;
return max(min(.7 * f / length(df), .1), length(position) - 1.7);
}

float map(in vec3 position)
{
return sdGoursat(position / 45., 5. / 12.) * 45.;
}