R"###(  
#version 330 core

out vec4 FragColor;
in vec2 texCoords;

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

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

void main()
{
    vec3 ray = vec3(texCoords.x, texCoords.y,2.0f);
    ray = (ray - 0.5f) * 2;
    vec3 pos = ray;
    float min = sphereMin(ray);

    while( (min < 100.0f) && (min > 0.1f) ) {
        ray = normalize(ray);
        ray = ray * min;
        pos = pos + ray;
        min = sphereMin(pos);
    }
    
    
    if(min <= 0.2f){
        FragColor = vec4(texCoords.x, texCoords.y, 0.2f, 1.0f);
    } else {
        FragColor = vec4(0.0f,0.0f,0.0f,1.0f);
    }

} 
)###";