R"###(  
#version 330 core

out vec4 FragColor;
in vec2 texCoords;

uniform float aspect;

vec3 center = vec3(0.0,0.0,20.0);
float radius = 5.0;

float planeHeight = -7.0;

struct Ray {
    vec3 dir;
    vec3 pos;
    float min;
    float len;
    vec3 color;
};
        
Ray applyMin(Ray ray) {
    vec3 off = ray.dir * ray.min;
    ray.pos = ray.pos + off;
    ray.len = ray.len +  ray.min;
    return ray;
}


float planeMin(vec3 pos){
    return pos.y - planeHeight;
}

float sphereMin(vec3 pos){
    return length(pos - center) - radius;
}

Ray minFn(Ray ray){
    float sp = sphereMin(ray.pos);
    float pl = planeMin(ray.pos);


    

    if (sp < pl){
        ray.color = vec3(1.0, 0.5, 0.2);
        ray.min = sp;
    } else {
        ray.color = vec3(0.2, 0.3, 0.3);
        ray.min = pl;
    }
    return applyMin(ray);
    }

float minFn(vec3 pos){
    float sp = sphereMin(pos);
    float pl = planeMin(pos);

    if (sp < pl){
        return sp;
    } else {
        return pl;
    }
}

Ray march(Ray ray){
    //ray.min = minFn(ray.pos);
    ray = minFn(ray);
    int c = 0;
    while(( c < 200) && (ray.min < 100.0f) && (ray.min > 0.1f) ) {
        ray = minFn(ray);    
        c++;
    }

    return ray;
}

vec3 calcNormal(Ray ray){

    float h = 0.001;
    float m = sphereMin(ray.pos);
    vec3 n = vec3(
        minFn(ray.pos + vec3( h,.0,.0)) - minFn(ray.pos - vec3( h,.0,.0)),
        minFn(ray.pos + vec3(.0, h,.0)) - minFn(ray.pos - vec3(.0, h,.0)),
        minFn(ray.pos + vec3(.0,.0, h)) - minFn(ray.pos - vec3(.0,.0, h))
    );

    return normalize(n);
}

void main()
{
    vec3 dir = vec3((texCoords - 0.5)*2,1.0);
    dir.x *= aspect;
    vec3 pos = dir;
    Ray ray = Ray(normalize(dir),pos,.0,.0,vec3(.0));

    ray = march(ray);

    vec3 normal = calcNormal(ray);

    vec3 lighDir = normalize(vec3(.5,-1.0,0.5));
    float light = (- min(dot(normal,lighDir),0.0))*0.85+0.3;

    Ray shRay = Ray(lighDir * (-1.0), ray.pos + 0.5*normal , .0,.0, vec3(.0));
    shRay = march(shRay);

    if( (dot(lighDir,normal) < 0.0) && (shRay.len <20)){
        light *= min(shRay.len*0.1,1.0);
    }

    if(ray.min <= 0.2){
        FragColor = vec4(ray.color * light, 1.0);
    } else {
        FragColor = vec4(.0,0.0,0.0,1.0);
    }

} 
)###";