frag.glsl

#version 330

// Input vertex attributes (from vertex shader)
in vec2 fragTexCoord;
in vec4 fragColor;
in vec3 fragPosition;
in vec3 fragPositionWorld;
in vec3 fragNormal;
in vec3 rayDir;

uniform mat4 mvp;

uniform vec4 colDiffuse;

// Output fragment color
out vec4 finalColor;
#define fbm_steps 6
#define wall_height 5.0
#define outer_wall_height 10.0
#define sky_extents 1000.0
#define PI 3.14159265359

vec4 gray(float color) {
    return vec4(color, color, color, 1.0);
}

float rand(vec2 co) {
    return fract(sin(dot(co, vec2(839.27, -312.39))) * 21890.29);
}

float value_noise(vec2 co) {
    vec2 base = floor(co);
    float ul = rand(base);
    float ur = rand(base + vec2(1.0, 0.0));
    float ll = rand(base + vec2(0.0, 1.0));
    float lr = rand(base + vec2(1.0, 1.0));
    float u = mix(ul, ur, fract(co.x));
    float l = mix(ll, lr, fract(co.x));
    return mix(u, l, fract(co.y));
}

float rand_3d(vec3 co) {
    return fract(sin(dot(co, vec3(839.27, -312.39, 895.12))) * 21890.29);
}

float value_noise_3d(vec3 co) {
    vec3 base = floor(co);
    float ulb = rand_3d(base);
    float ulf = rand_3d(base + vec3(1.0, 0.0, 0.0));
    float urb = rand_3d(base + vec3(0.0, 1.0, 0.0));
    float urf = rand_3d(base + vec3(1.0, 1.0, 0.0));
    float llb = rand_3d(base + vec3(0.0, 0.0, 1.0));
    float llf = rand_3d(base + vec3(1.0, 0.0, 1.0));
    float lrb = rand_3d(base + vec3(0.0, 1.0, 1.0));
    float lrf = rand_3d(base + vec3(1.0, 1.0, 1.0));
    float ul = mix(ulb, ulf, fract(co.x));
    float ur = mix(urb, urf, fract(co.x));
    float ll = mix(llb, llf, fract(co.x));
    float lr = mix(lrb, lrf, fract(co.x));
    float u = mix(ul, ur, fract(co.y));
    float l = mix(ll, lr, fract(co.y));
    return mix(u, l, fract(co.z));
}

float fbm(vec2 st) {
    vec2 coord = st;
    float value = 0.0;
    float amp_mul = 0.5;
    float amplitude = 1.0 - amp_mul;
    float frequency = 1.0;
    vec2 offset = vec2(0.312, -0.732);
    float angle = 0.13;
    // mat2 rotation = mat2(cos(angle), sin(angle), -sin(angle), cos(angle));
    for (int i = 0; i < fbm_steps; i++) {
        value += amplitude * value_noise(coord * frequency);
        coord += offset;
        // coord = rotation * coord;
        frequency *= 2.0;
        amplitude *= amp_mul;
    }
    return value;
}

float fbm_3d(vec3 st) {
    vec3 coord = st;
    float value = 0.0;
    float amp_mul = 0.5;
    float amplitude = 1.0 - amp_mul;
    float frequency = 1.0;
    // vec3 offset = vec3(0.312, -0.732, 0.183);
    vec3 offset = vec3(-0.732, 0.312, 0.183);
    float angle = 0.13;
    // mat2 rotation = mat2(cos(angle), sin(angle), -sin(angle), cos(angle));
    for (int i = 0; i < fbm_steps; i++) {
        value += amplitude * value_noise_3d(coord * frequency);
        coord += offset;
        // coord = rotation * coord;
        // coord.xz = rotation * coord.xz;
        // coord.xy = rotation * coord.xy;
        frequency *= 2.0;
        amplitude *= amp_mul;
    }
    return value;
}

mat2 rot_matrix(float angle) {
    return mat2(cos(angle), sin(angle), -sin(angle), cos(angle));
}

vec3 darkGreen = vec3(0.1, 0.2, 0.1) / 0.5;
vec3 slightlyLighterGreen = vec3(0.2, 0.3, 0.2) / 0.5;
// vec3 darkBrown = vec3(0.2, 0.1, 0.0) / 0.6;
vec3 darkBrown = vec3(0.2, 0.1, 0.1) / 0.6;
// vec3 brown = vec3(0.35, 0.25, 0.1) / 0.6;
vec3 brown = vec3(0.35, 0.25, 0.3) / 0.6;
vec3 darkestBrown = darkBrown * (darkBrown / brown);

void main() {
    if (colDiffuse.r == 0.0 && colDiffuse.g == 1.0 && colDiffuse.b == 1.0) {
        // finalColor = gray(fragPositionWorld.y / 70.0 + 0.1);
        float height = fragPositionWorld.y / wall_height;
        finalColor = vec4(mix(darkBrown, brown, sqrt(height)), 1.0);
    } else if (fragColor.r == 0.0 && fragColor.g == 1.0 && fragColor.b == 0.0) {
        // float noiseValue = fbm(fragPositionWorld.xz * 0.2);
        // vec3 color = mix(darkestBrown, darkBrown, noiseValue);
        vec3 color = darkBrown;

        finalColor = vec4(color, 1.0);
    } else if (colDiffuse.r == 1.0 && colDiffuse.g == 1.0 && colDiffuse.b == 0.0) {
        float height = fragPositionWorld.y / outer_wall_height;
        finalColor = vec4(mix(darkBrown, brown, height), 1.0);
    } else if (colDiffuse.r == 0.0 && colDiffuse.g == 0.0 && colDiffuse.b == 1.0) {
        vec3 skyDir = fragPositionWorld / (sky_extents / 200.0);
        vec3 resultColor = vec3(0.0);
        float star_thresh = 0.7;
        // float col_range = PI / 2;
        float col_range = PI / 6;
        float col_shift = 0;
        float color_div = 4.0;
        for (int i = 0; i < 3; i++) {
            float noiseValue = fbm_3d(skyDir);
            float grays = max(0.0, noiseValue - star_thresh) * 10;
            float color = max(0.0, noiseValue - star_thresh + 0.01) * 10;
            vec3 starColor = vec3(0.0, 0.0, 1.0);
            starColor.xz = rot_matrix(col_shift-fbm_3d(skyDir.xzy / color_div) * col_range) * starColor.xz;
            // resultColor += gray(grays).rgb + color * starColor;
            resultColor = max(resultColor, gray(grays).rgb + color * starColor);
            skyDir /= sqrt(30.0);
            star_thresh -= 0.05;
            col_range *= 2;
            color_div /= 2.0;
        }
        finalColor = vec4(resultColor, 1.0);
    } else {
        finalColor = fragColor;
    }
}