GLSL: fire

glsl-fire.markdown

GLSL: fire

fbm + voronoi fire rings

A Pen by Stranger in the Q on CodePen.

License.

index.html

<canvas id="canvas"></canvas>
<script type="glsl">
precision highp float;
uniform float time;      
uniform vec2 resolution;  
    
// taken from https://www.shadertoy.com/view/4tlSzl
    
vec3 firePalette(float i) {
    float T = 1400. + 1300.*i; 
    vec3 L = vec3(7.4, 5.6, 4.4); 
    L = pow(L,vec3(5.0)) * (exp(1.43876719683e5/(T*L))-1.0);
    return 1.0-exp(-5e8/L); 
}    

vec3 hash33(vec3 p) { 
    float n = sin(dot(p, vec3(7, 157, 113)));    
    return fract(vec3(2097152, 262144, 32768)*n); 
}

float voronoi(vec3 p) {
	vec3 b, r, g = floor(p);
	p = fract(p); 
	float d = 1.; 
	for(int j = -1; j <= 1; j++) {
	    for(int i = -1; i <= 1; i++) {
		    b = vec3(i, j, -1);
		    r = b - p + hash33(g+b);
		    d = min(d, dot(r,r));
		    b.z = 0.0;
		    r = b - p + hash33(g+b);
		    d = min(d, dot(r,r));
		    b.z = 1.;
		    r = b - p + hash33(g+b);
		    d = min(d, dot(r,r));	
	    }
	}
	return d;
}

float noiseLayers(in vec3 p) {
    vec3 t = vec3(0., 0., p.z+time); 
    float tot = 0., sum = 0., amp = 1.; 
    for (int i = 0; i < 6; i++) {
        tot += voronoi(p + t) * amp; 
        p *= 2.0; 
        t *= 1.5; 
        sum += amp; 
        amp *= 0.5; 
    }
    return tot/sum; 
}
      
void main(void) {
    vec2 uv = (gl_FragCoord.xy - resolution.xy*0.5)/ resolution.y;
    vec3 rd = normalize(vec3(uv.x, uv.y, 3.1415/8.));
    float c = noiseLayers(rd*4.); 
    vec3 col = firePalette(c);
    gl_FragColor = vec4(sqrt(col), 1.);  
}
</script>

script.js

let gl = canvas.getContext('webgl');
gl.bindBuffer(gl.ARRAY_BUFFER, gl.createBuffer());
gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([-1,3,-1,-1,3,-1]), gl.STATIC_DRAW);

let pid = gl.createProgram();
shader(`attribute vec2 v;void main(void){gl_Position=vec4(v,0.,1.);}`,gl.VERTEX_SHADER);
shader(document.querySelector(`script[type="glsl"]`).textContent,gl.FRAGMENT_SHADER);
gl.linkProgram(pid);
gl.useProgram(pid);

let v = gl.getAttribLocation(pid, "v");
gl.vertexAttribPointer(v, 2, gl.FLOAT, false, 0, 0);
gl.enableVertexAttribArray(v);

let resolution = gl.getUniformLocation(pid, 'resolution');
let time = gl.getUniformLocation(pid, 'time');
let fill = gl.getUniformLocation(pid, 'fill');
requestAnimationFrame(draw);

function draw(t) {
  gl.uniform1f(time, t/1000);
  gl.drawArrays(gl.TRIANGLES, 0, 3);
  requestAnimationFrame(draw);
}

function shader(src, type) {
  let sid = gl.createShader(type);
  gl.shaderSource(sid, src);
  gl.compileShader(sid);
  var message = gl.getShaderInfoLog(sid);
  gl.attachShader(pid, sid);
  if (message.length > 0) {
    console.log(src.split("\n").map((str, i) => 
       (""+(1+i)).padStart(4, "0")+": "+str).join("\n"));
    throw message;
  }
}
    
addEventListener('resize', function(){
    if (innerWidth === canvas.width && 
        innerHeight === canvas.height )
        return;
    canvas.width = innerWidth;
    canvas.height = innerHeight;
    gl.uniform2f(resolution, gl.drawingBufferWidth, gl.drawingBufferHeight);
    gl.viewport(0, 0, gl.drawingBufferWidth, gl.drawingBufferHeight);
})

dispatchEvent(new Event('resize'))

style.css

body {
    overflow:hidden;
    margin:0;
}

tour.json

{
  "title": "GLSL: fire ",
  "description": "GLSL: fire ",
  "steps": [
    {
      "file": "index.html",
      "line": 7,
      "description": "# Heading\n\nOne"
    },
    {
      "file": "style.css",
      "line": 3,
      "description": "Two"
    },
    {
      "file": "script.js",
      "line": 7,
      "description": "Three"
    }
  ]
}