float distanceFunction(vec3 p) {
    return length(p) - 1.0; // This is the distance to a sphere at (0,0,0), radius 1.0
}

vec3 rgb = vec3(0.0); // start with black pixel

vec3 camPos = vec3(0, 0, -10); // starting point for the ray
vec3 rayDir = normalize(uv, 1); // direction of the ray

vec3 pos = camPos; // This is the current position

for(int j=0; j<100; j++) {
    float dist = distanceFunction(pos); // distance to surface
    if (dist < 0.001) {
        // We’re close enough, call it a hit
        rgb = vec3(1.0); // colour the pixel white
        break; // exit the loop because we hit the surface
    }

    pos += rayDir * dist; // move along the ray by the SDF distance
}