如何创建多色噪声着色器

Question

我需要一个采用 3 种输入颜色并生成噪声的着色器，如下所示。在“噪声纹理”和“颜色渐变”节点的帮助下，在 Blender 中很容易实现。

我找到了 this gist，这可能会解决我的问题。但是我无法配置颜色。而且噪音看起来比 Blender 中的结果“更尖锐”。

我是否需要为此编写自己的着色器，或者是否有更简单的方法使用 ThreeJS 实现此效果？

Answer 1

基本上，您只需要两件事：

着色器中的噪声函数
渐变纹理。

我选择了 FBM 作为噪声，并使用 .onBeforeCompile() 改变了一个内置的 material（标准）：

body{
  overflow: hidden;
  margin: 0;
}

<canvas id="cnvsGradient" width="300" height="50" style="position: absolute; margin: 10px; border: 1px solid aqua"/>

<script>
  // https://github.com/yiwenl/glsl-fbm/blob/master/3d.glsl
  const fbm = `
  #define NUM_OCTAVES 5

  float mod289(float x){return x - floor(x * (1.0 / 289.0)) * 289.0;}
  vec4 mod289(vec4 x){return x - floor(x * (1.0 / 289.0)) * 289.0;}
  vec4 perm(vec4 x){return mod289(((x * 34.0) + 1.0) * x);}

  float noise(vec3 p){
      vec3 a = floor(p);
      vec3 d = p - a;
      d = d * d * (3.0 - 2.0 * d);

      vec4 b = a.xxyy + vec4(0.0, 1.0, 0.0, 1.0);
      vec4 k1 = perm(b.xyxy);
      vec4 k2 = perm(k1.xyxy + b.zzww);

      vec4 c = k2 + a.zzzz;
      vec4 k3 = perm(c);
      vec4 k4 = perm(c + 1.0);

      vec4 o1 = fract(k3 * (1.0 / 41.0));
      vec4 o2 = fract(k4 * (1.0 / 41.0));

      vec4 o3 = o2 * d.z + o1 * (1.0 - d.z);
      vec2 o4 = o3.yw * d.x + o3.xz * (1.0 - d.x);

      return o4.y * d.y + o4.x * (1.0 - d.y);
  }


  float fbm(vec3 x) {
    float v = 0.0;
    float a = 0.5;
    vec3 shift = vec3(100);
    for (int i = 0; i < NUM_OCTAVES; ++i) {
      v += a * noise(x);
      x = x * 2.0 + shift;
      a *= 0.5;
    }
    return v;
  }
  `;
</script>
<script type="module">
console.clear();

import * as THREE from "https://cdn.skypack.dev/three@0.136.0";
import {OrbitControls} from "https://cdn.skypack.dev/three@0.136.0/examples/jsm/controls/OrbitControls.js";

let scene = new THREE.Scene();
let camera = new THREE.PerspectiveCamera(60, innerWidth / innerHeight, 1, 100);
camera.position.set(0, 0, 10);
let renderer = new THREE.WebGLRenderer();
renderer.setSize(innerWidth, innerHeight);
renderer.setClearColor(0x444444);
document.body.appendChild(renderer.domElement);

let controls = new OrbitControls(camera, renderer.domElement);

let light = new THREE.DirectionalLight(0xffffff);
light.position.setScalar(10);
scene.add(light);
scene.add(new THREE.AmbientLight(0xffffff, 0.5));

let g = new THREE.CylinderBufferGeometry(2, 1, 5, 6, 64);

let pos = g.attributes.position;
let v = new THREE.Vector3();
let axis = new THREE.Vector3(0, 1, 0);
for(let i = 0; i < pos.count; i++){
  v.fromBufferAttribute(pos, i);
  let ratio = (v.y - (-2.5)) / 5;
  v.applyAxisAngle(axis, THREE.MathUtils.degToRad(60) * ratio);
  pos.setXYZ(i, v.x, v.y, v.z);
}
g.computeVertexNormals();

let uniforms = {
  tex: {
    value: setGradient()
  }
}
let m = new THREE.MeshStandardMaterial({
  metalness: 0.25,
  roughness: 0.75,
  onBeforeCompile: shader => {
    shader.uniforms.tex = uniforms.tex;
    shader.vertexShader = `
      varying vec3 vPos;
      ${shader.vertexShader}
    `.replace(
      `#include <begin_vertex>`,
      `#include <begin_vertex>
      //vPos = (modelMatrix * vec4(position, 1.0)).xyz;
      vPos = vec3(position);
      `
    );
    //console.log(shader.vertexShader);
    shader.fragmentShader = `
      uniform sampler2D tex;
      varying vec3 vPos;
      ${fbm}
      ${shader.fragmentShader}      
    `.replace(
      `vec4 diffuseColor = vec4( diffuse, opacity );`,
      `
      float d = fbm(vPos * 0.5);
      for(int i = 0; i < 4; i++){
        d = fbm(vPos * (float(i) + 1.) * d);
      }

      vec3 col = texture(tex, vec2(d, 0.5)).rgb;
      vec4 diffuseColor = vec4( col, opacity );`
    );
    //console.log(shader.fragmentShader);
  }
});
let o = new THREE.Mesh(g, m);
scene.add(o);

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

renderer.setAnimationLoop(() => {
  o.rotation.y += 0.01;
  renderer.render(scene, camera);
});

function setGradient(){
  
  let canvas = document.getElementById('cnvsGradient');
  let ctx = canvas.getContext('2d');

  let gradient = ctx.createLinearGradient(0,0, 300,0);

  gradient.addColorStop(0.15, 'yellow');
  gradient.addColorStop(.5, 'red');
  gradient.addColorStop(0.85, 'blue');

  ctx.fillStyle = gradient;
  ctx.fillRect(0, 0, canvas.width, canvas.height);
  
  return new THREE.CanvasTexture(canvas);

}

function onWindowResize() {

  camera.aspect = innerWidth / innerHeight;
  camera.updateProjectionMatrix();

  renderer.setSize( innerWidth, innerHeight );

}
</script>

如何创建多色噪声着色器

How to Create a Multi-Colored Noise Shader

shader

glsl

blender

three.js