2d_test_nebula.tres

[gd_resource type="Shader" format=3 uid="uid://cfcpnnboa7jya"]

[resource]
code = "shader_type canvas_item;

uniform vec2 offset;
uniform float scale;

uniform float density;
uniform float falloff;
uniform vec3 color;

uniform vec3 color2;

// GLSL textureless classic 2D noise \"cnoise\",
// with an RSL-style periodic variant \"pnoise\".
// Author:  Stefan Gustavson (stefan.gustavson@liu.se)
// Version: 2011-08-22
//
// Many thanks to Ian McEwan of Ashima Arts for the
// ideas for permutation and gradient selection.
//
// Copyright (c) 2011 Stefan Gustavson. All rights reserved.
// Distributed under the MIT license. See LICENSE file.
// https://github.com/stegu/webgl-noise
//

vec4 mod289(vec4 x) {
    return x - floor(x * (1.0 / 289.0)) * 289.0;
}

vec4 permute(vec4 x) {
    return mod289(((x * 34.0) + 1.0) * x);
}

vec4 taylorInvSqrt(vec4 r) {
    return 1.79284291400159 - 0.85373472095314 * r;
}

vec2 fade(vec2 t) {
    return t * t * t * (t * (t * 6.0 - 15.0) + 10.0);
}

// Classic Perlin noise
float cnoise(vec2 P) {
    vec4 Pi = floor(vec4(P, P)) + vec4(0.0, 0.0, 1.0, 1.0);
    vec4 Pf = fract(vec4(P, P)) - vec4(0.0, 0.0, 1.0, 1.0);
    Pi = mod289(Pi); // To avoid truncation effects in permutation
    vec4 ix = Pi.xzxz;
    vec4 iy = Pi.yyww;
    vec4 fx = Pf.xzxz;
    vec4 fy = Pf.yyww;

    vec4 i = permute(permute(ix) + iy);

    vec4 gx = fract(i * (1.0 / 41.0)) * 2.0 - 1.0 ;
    vec4 gy = abs(gx) - 0.5 ;
    vec4 tx = floor(gx + 0.5);
    gx = gx - tx;

    vec2 g00 = vec2(gx.x,gy.x);
    vec2 g10 = vec2(gx.y,gy.y);
    vec2 g01 = vec2(gx.z,gy.z);
    vec2 g11 = vec2(gx.w,gy.w);
    
    vec4 norm = taylorInvSqrt(vec4(dot(g00, g00), dot(g01, g01), dot(g10, g10), dot(g11, g11)));
    g00 *= norm.x;
    g01 *= norm.y;
    g10 *= norm.z;
    g11 *= norm.w;
    
    float n00 = dot(g00, vec2(fx.x, fy.x));
    float n10 = dot(g10, vec2(fx.y, fy.y));
    float n01 = dot(g01, vec2(fx.z, fy.z));
    float n11 = dot(g11, vec2(fx.w, fy.w));
    
    vec2 fade_xy = fade(Pf.xy);
    vec2 n_x = mix(vec2(n00, n01), vec2(n10, n11), fade_xy.x);
    float n_xy = mix(n_x.x, n_x.y, fade_xy.y);
    return 2.3 * n_xy;
}

// Classic Perlin noise, periodic variant
float pnoise(vec2 P, vec2 rep) {
    vec4 Pi = floor(vec4(P, P)) + vec4(0.0, 0.0, 1.0, 1.0);
    vec4 Pf = fract(vec4(P, P)) - vec4(0.0, 0.0, 1.0, 1.0);
    Pi = mod(Pi, vec4(rep, rep)); // To create noise with explicit period
    Pi = mod289(Pi); // To avoid truncation effects in permutation
    vec4 ix = Pi.xzxz;
    vec4 iy = Pi.yyww;
    vec4 fx = Pf.xzxz;
    vec4 fy = Pf.yyww;
    
    vec4 i = permute(permute(ix) + iy);
    
    vec4 gx = fract(i * (1.0 / 41.0)) * 2.0 - 1.0 ;
    vec4 gy = abs(gx) - 0.5 ;
    vec4 tx = floor(gx + 0.5);
    gx = gx - tx;
    
    vec2 g00 = vec2(gx.x,gy.x);
    vec2 g10 = vec2(gx.y,gy.y);
    vec2 g01 = vec2(gx.z,gy.z);
    vec2 g11 = vec2(gx.w,gy.w);
    
    vec4 norm = taylorInvSqrt(vec4(dot(g00, g00), dot(g01, g01), dot(g10, g10), dot(g11, g11)));
    g00 *= norm.x;
    g01 *= norm.y;
    g10 *= norm.z;
    g11 *= norm.w;

    float n00 = dot(g00, vec2(fx.x, fy.x));
    float n10 = dot(g10, vec2(fx.y, fy.y));
    float n01 = dot(g01, vec2(fx.z, fy.z));
    float n11 = dot(g11, vec2(fx.w, fy.w));
    
    vec2 fade_xy = fade(Pf.xy);
    vec2 n_x = mix(vec2(n00, n01), vec2(n10, n11), fade_xy.x);
    float n_xy = mix(n_x.x, n_x.y, fade_xy.y);
    return 2.3 * n_xy;
}

float normalnoise(vec2 p) {
     return cnoise(p) * 0.5 + 0.5;
}

float noise(vec2 p) {
    p += offset;
    int steps = 5;
    float n_scale = pow(2.0, float(steps));
    float displace = 0.0;
    for (int i = 0; i < steps; i++) {
        displace = normalnoise(p * n_scale + displace);
        n_scale *= 0.5;
    }
    return normalnoise(p + displace);
}


void fragment() {
	//tyro
	//float n = noise(UV*scale*1.0);
	float or_n = noise(FRAGCOORD.xy*scale *1.0);
	float n = pow(or_n + density, falloff);
	
	float col_n = noise(FRAGCOORD.xy*scale*0.5);
	
	vec3 col = mix(color, color2, col_n);
	//vec3 col = color + color2;
	
	//COLOR.rgb = col;
	float mixi = n;
	//float mixi = 1.0-(pow(n, density));
	//for aesthetic reasons, black (background) must not be a minority but be noticeable
	COLOR.rgb = mix(vec3(0.0), col, mixi);
	
    //COLOR.rgb = vec3(or_n);
}"