#version 300 es
precision highp float;

// Inputs
in vec2 texture_coordinates;
uniform float time;
uniform sampler2D uSampler1;
uniform sampler2D uSampler2;
uniform vec3 camera_pos;

// Output
out vec4 color;

const float PI = 3.1415;

// Raymarching variables
#define MAX_ITERATIONS 20
#define MIN_TOLERANCE .01

//const vec3 camera_pos = vec3(0.);
const vec3 color1 = vec3(0.494, 0.361, 0.678);
const vec3 color2 = vec3(0.827, 0.945, 0.875);

// Scene Object (sphere)

// returns the distance from the ray to this sphere in the scene
float sphere_render(vec3 ray_pos, float radius, vec3 sphere_pos) {
    return distance(ray_pos, sphere_pos) - radius;
}

float remap11(float val) {
    return ((val - .5) * 2.);
}

void main() {

    // Set up camera and sphere object
    vec3 ray_dir = normalize(vec3(remap11(texture_coordinates.x), remap11(texture_coordinates.y), 1.));
    vec3 ray_pos = camera_pos;
    const vec3 sphere_pos = vec3(0., 0., 3.);
    const float rad = 1.;

    for (int i = 0; i < MAX_ITERATIONS; i++) {
        float distance = sphere_render(ray_pos, rad, sphere_pos);

        // Check If within tolerances
        if (distance < MIN_TOLERANCE) {
            break;
        }

        ray_pos += (distance * ray_dir);
        color = vec4(mix(color1, color2, float(i) / float(MAX_ITERATIONS)), 1.);
    }

    // Image stuff for later
    /*
      if ((texture_coordinates.x + texture_coordinates.y) > 1.) {
        color = texture(uSampler1, texture_coordinates);
      }
      else {
        color = texture(uSampler2, texture_coordinates);
      }*/

    // Basic color time shift
    // color = vec4( texture_coordinates, (sin( time * PI) + 1.)/2. , 1.);
}