火焰（ flame）

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示例

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/88/three.min.js"></script>
<script id="vertexShader" type="x-shader/x-vertex">
    void main() {
        gl_Position = vec4( position, 1.0 );
    }
</script>
<script id="fragmentShader" type="x-shader/x-fragment">
  uniform vec2 u_resolution;
  uniform vec2 u_mouse;
  uniform float u_time;
  uniform sampler2D u_noise;

  #define PI 3.14159265359
  #define TAU 6.283185307179586
  
  
  float tri( float x ) { 
    return abs( fract(x) - .5 );
  }

  vec3 tri3( vec3 p ){

    return vec3( 
        tri( p.z + tri( p.y * 6. ) ), 
        tri( p.z + tri( p.x * 2. ) ), 
        tri( p.y + tri( p.x * 6. ) )
    );

  }
  float triNoise3D( vec3 p, float spd , float time){

    float z  = 1.4;
    float rz =  0.;
    vec3  bp =   p;

    for( float i = 0.; i <= 3.; i++ ){

      vec3 dg = tri3( bp * 2. );
      p += ( dg + time * .1 * spd );

      bp *= 1.8;
      z  *= 1.5;
      p  *= 1.2; 

      float t = tri( p.z + tri( p.x + tri( p.y )));
      rz += t / z;
      bp += 0.14;

    }

    return rz;

  }
  

  void main() {
    
    float scale = .4;
    vec2 uv = (gl_FragCoord.xy - 0.5 * u_resolution.xy) / min(u_resolution.y, u_resolution.x);
        
    vec3 highlightColour;
    vec3 bodyColour;
    vec3 bgColour = mix(vec3(0., .0, .2), vec3(.6,.65,.1) * .5, uv.y + .2);
    bgColour += (2. - length(uv * 1.5)) * .4;
    
    vec2 pos = uv / .5;
    float bottom = 0.5*(pos.y+1.0) * sin(u_time);
    vec2 wave = vec2(0.);
    wave.x += bottom*sin(4.0*pos.y-8.0*u_time)*.5;
    
    pos += .25*wave;
    pos.x += pos.x / (1.0-(pos.y));
    
    float flameMask = clamp(1.0-length(pos), 0.0, 1.0);
    flameMask = 1.0-pow(1.0-flameMask, 4.);
    
    bodyColour = mix(vec3(0.5,0.2,0.2), vec3(0.55,0.25,0.0), uv.y + flameMask);
    highlightColour = mix(vec3(1.0,.5,0.0), vec3(1.0,2.0,0.0), uv.y * (1. - flameMask * flameMask));
    
    vec3 uv3d = scale*0.1*vec3(uv.x, uv.y, 0.0);
    uv3d += vec3(0.0, -u_time*0.04, u_time*0.02);
    float noise = triNoise3D(uv3d * 5. + flameMask * .05, 0., u_time);
    noise = noise * 1.5 - .2;
    
    vec3 colour;
    
    float value = flameMask*noise;    
    value += .5*flameMask;

    float flame_edge = flameMask * 0.3*(pos.y+1.0);
    float edge = clamp(value-flame_edge*2., 0.0 , 1.0);
    float hardMask = smoothstep(flame_edge,flame_edge+0.1, value);
    float highlight = 1.0-edge*edge;
        
    uv3d = vec3(uv.x, uv.y, 0.0) + vec3(0.0, -u_time*0.01, u_time*0.025);

    highlight = pow(highlight, 2.0);
        
    // colour += glow * 2.;
    colour = highlightColour*(hardMask*highlight);
    colour = mix(bgColour, colour, hardMask);
    colour += bodyColour*flameMask*flameMask;
    
    gl_FragColor = vec4(colour,1.0);
  }
</script>
<div id="container" touch-action="none"></div>

CSS

body {
  margin: 0;
  padding: 0;
}

#container {
  position: fixed;
  touch-action: none;
}

JS

/*
Most of the stuff in here is just bootstrapping. Essentially it's just
setting ThreeJS up so that it renders a flat surface upon which to draw 
the shader. The only thing to see here really is the uniforms sent to 
the shader. Apart from that all of the magic happens in the HTML view
under the fragment shader.
*/

let container;
let camera, scene, renderer;
let uniforms;

let loader=new THREE.TextureLoader();
let texture;
loader.setCrossOrigin("anonymous");
loader.load(
  'https://s3-us-west-2.amazonaws.com/s.cdpn.io/982762/noise.png',
  function do_something_with_texture(tex) {
    texture = tex;
    texture.wrapS = THREE.RepeatWrapping;
    texture.wrapT = THREE.RepeatWrapping;
    texture.minFilter = THREE.LinearFilter;
    init();
    animate();
  }
);

function init() {
  container = document.getElementById( 'container' );

  camera = new THREE.Camera();
  camera.position.z = 1;

  scene = new THREE.Scene();

  var geometry = new THREE.PlaneBufferGeometry( 2, 2 );

  uniforms = {
    u_time: { type: "f", value: 1.0 },
    u_resolution: { type: "v2", value: new THREE.Vector2() },
    u_noise: { type: "t", value: texture },
    u_mouse: { type: "v2", value: new THREE.Vector2() }
  };

  var material = new THREE.ShaderMaterial( {
    uniforms: uniforms,
    vertexShader: document.getElementById( 'vertexShader' ).textContent,
    fragmentShader: document.getElementById( 'fragmentShader' ).textContent
  } );
  material.extensions.derivatives = true;

  var mesh = new THREE.Mesh( geometry, material );
  scene.add( mesh );

  renderer = new THREE.WebGLRenderer();
  renderer.setPixelRatio( window.devicePixelRatio );

  container.appendChild( renderer.domElement );

  onWindowResize();
  window.addEventListener( 'resize', onWindowResize, false );

  document.addEventListener('pointermove', (e)=> {
    let ratio = window.innerHeight / window.innerWidth;
    uniforms.u_mouse.value.x = (e.pageX - window.innerWidth / 2) / window.innerWidth / ratio;
    uniforms.u_mouse.value.y = (e.pageY - window.innerHeight / 2) / window.innerHeight * -1;
    
    e.preventDefault();
  });
}

function onWindowResize( event ) {
  renderer.setSize( window.innerWidth, window.innerHeight );
  uniforms.u_resolution.value.x = renderer.domElement.width;
  uniforms.u_resolution.value.y = renderer.domElement.height;
}

function animate(delta) {
  requestAnimationFrame( animate );
  render(delta);
}






let capturer = new CCapture( { 
  verbose: true, 
  framerate: 60,
  // motionBlurFrames: 4,
  quality: 90,
  format: 'webm',
  workersPath: 'js/'
 } );
let capturing = false;

isCapturing = function(val) {
  if(val === false && window.capturing === true) {
    capturer.stop();
    capturer.save();
  } else if(val === true && window.capturing === false) {
    capturer.start();
  }
  capturing = val;
}
toggleCapture = function() {
  isCapturing(!capturing);
}

window.addEventListener('keyup', function(e) { if(e.keyCode == 68) toggleCapture(); });

let then = 0;
function render(delta) {
  
  uniforms.u_time.value = delta * 0.0005;
  renderer.render( scene, camera );
  
  if(capturing) {
    capturer.capture( renderer.domElement );
  }
}