// Name: Octograms
// Author: whisky_shusuky
// URL: https://www.shadertoy.com/view/tlVGDt
#version 330 core
precision highp float;

out vec4 FragColor;
in vec2 vUV;
uniform vec2 iResolution;
uniform float iTime;

float gTime = 0.0;
const float REPEAT = 5.0;

// rotación 2D
mat2 rot(float a) {
    float c = cos(a), s = sin(a);
    return mat2(c, s, -s, c);
}

float sdBox(vec3 p, vec3 b) {
    vec3 q = abs(p) - b;
    return length(max(q, vec3(0.0))) + min(max(q.x, max(q.y, q.z)), 0.0);
}

float boxGeom(vec3 pos, float scale) {
    pos *= scale;
    float base = sdBox(pos, vec3(.4, .4, .1)) / 1.5;
    pos.xy *= 5.0;
    pos.y -= 3.5;
    pos.xy *= rot(.75);
    float result = -base;
    return result;
}

float box_set(vec3 pos, float iTimeLocal) {
    vec3 pos_origin = pos;
    pos = pos_origin;
    pos.y += sin(gTime * 0.4) * 2.5;
    pos.xy *= rot(.8);
    float box1 = boxGeom(pos, 2.0 - abs(sin(gTime * 0.4)) * 1.5);

    pos = pos_origin;
    pos.y -= sin(gTime * 0.4) * 2.5;
    pos.xy *= rot(.8);
    float box2 = boxGeom(pos, 2.0 - abs(sin(gTime * 0.4)) * 1.5);

    pos = pos_origin;
    pos.x += sin(gTime * 0.4) * 2.5;
    pos.xy *= rot(.8);
    float box3 = boxGeom(pos, 2.0 - abs(sin(gTime * 0.4)) * 1.5);

    pos = pos_origin;
    pos.x -= sin(gTime * 0.4) * 2.5;
    pos.xy *= rot(.8);
    float box4 = boxGeom(pos, 2.0 - abs(sin(gTime * 0.4)) * 1.5);

    pos = pos_origin;
    pos.xy *= rot(.8);
    float box5 = boxGeom(pos, .5) * 6.0;

    pos = pos_origin;
    float box6 = boxGeom(pos, .5) * 6.0;

    float result = max(max(max(max(max(box1, box2), box3), box4), box5), box6);
    return result;
}

float mapScene(vec3 pos, float iTimeLocal) {
    return box_set(pos, iTimeLocal);
}

void mainImage(out vec4 fragColor, in vec2 fragCoord) {
    vec2 p = (fragCoord.xy * 2.0 - iResolution.xy) / min(iResolution.x, iResolution.y);
    vec3 ro = vec3(0.0, -0.2, iTime * 4.0);
    vec3 ray = normalize(vec3(p, 1.5));
    ray.xy = ray.xy * rot(sin(iTime * .03) * 5.0);
    ray.yz = ray.yz * rot(sin(iTime * .05) * .2);
    float t = 0.1;
    vec3 col = vec3(0.0);
    float ac = 0.0;

    for (int i = 0; i < 99; i++) {
        vec3 pos = ro + ray * t;
        pos = mod(pos - 2.0, 4.0) - 2.0;
        gTime = iTime - float(i) * 0.01;

        float d = mapScene(pos, iTime);

        d = max(abs(d), 0.01);
        ac += exp(-d * 23.0);

        t += d * 0.55;
    }

    col = vec3(ac * 0.02);
    col += vec3(0.0, 0.2 * abs(sin(iTime)), 0.5 + sin(iTime) * 0.2);

    fragColor = vec4(col, 1.0 - t * (0.02 + 0.02 * sin(iTime)));
}

void main() {
    vec2 fragCoordPixels = vUV * iResolution;
    vec4 outColor;
    mainImage(outColor, fragCoordPixels);
    FragColor = outColor;
}