#version 110

const vec3 ZERO = vec3(0.0, 0.0, 0.0);
const vec3 GREEN = vec3(0.0, 0.7, 0.0);
const vec3 YELLOW = vec3(0.5, 0.7, 0.0);
const vec3 RED = vec3(0.7, 0.0, 0.0);
const vec3 WHITE = vec3(1.0, 1.0, 1.0);
const float EPSILON = 0.0001;
const float BANDS_WIDTH = 10.0;

struct SlopeDetection
{
    bool actived;
	float normal_z;
    mat3 volume_world_normal_matrix;
};

uniform vec4 uniform_color;
uniform SlopeDetection slope;
uniform bool sinking;

#ifdef ENABLE_ENVIRONMENT_MAP
    uniform sampler2D environment_tex;
    uniform bool use_environment_tex;
#endif // ENABLE_ENVIRONMENT_MAP

varying vec3 clipping_planes_dots;

// x = diffuse, y = specular;
varying vec2 intensity;

varying vec3 delta_box_min;
varying vec3 delta_box_max;

varying vec4 model_pos;
varying float world_pos_z;
varying float world_normal_z;
varying vec3 eye_normal;

vec3 sinking_color(vec3 color)
{
    return (mod(model_pos.x + model_pos.y + model_pos.z, BANDS_WIDTH) < (0.5 * BANDS_WIDTH)) ? mix(color, ZERO, 0.6666) : color;
}

void main()
{
    if (any(lessThan(clipping_planes_dots, ZERO)))
        discard;
    vec3 color = uniform_color.rgb;
    float alpha = uniform_color.a;
    if (slope.actived && world_normal_z < slope.normal_z - EPSILON)
    {
        color = vec3(0.7, 0.7, 1.0);
        alpha = 1.0;
    }
    // if the fragment is outside the print volume -> use darker color
	color = (any(lessThan(delta_box_min, ZERO)) || any(greaterThan(delta_box_max, ZERO))) ? mix(color, ZERO, 0.3333) : color;
    // if the object is sinking, shade it with inclined bands or white around world z = 0
    if (sinking)
        color = (abs(world_pos_z) < 0.05) ? WHITE : sinking_color(color);
#ifdef ENABLE_ENVIRONMENT_MAP
    if (use_environment_tex)
        gl_FragColor = vec4(0.45 * texture2D(environment_tex, normalize(eye_normal).xy * 0.5 + 0.5).xyz + 0.8 * color * intensity.x, alpha);
    else
#endif
        gl_FragColor = vec4(vec3(intensity.y) + color * intensity.x, alpha);
}