threejs/manual/resources/threejs-textures.js

import * as THREE from 'three';
import {threejsLessonUtils} from './threejs-lesson-utils.js';

{
  const loader = new THREE.TextureLoader();

  function loadTextureAndPromise(url) {
    let textureResolve;
    const promise = new Promise((resolve) => {
      textureResolve = resolve;
    });
    const texture = loader.load(url, (texture) => {
      textureResolve(texture);
    });
    return {
      texture,
      promise,
    };
  }

  const filterTextureInfo = loadTextureAndPromise('/manual/resources/images/mip-example.png');
  const filterTexture = filterTextureInfo.texture;
  const filterTexturePromise = filterTextureInfo.promise;

  function filterCube(scale, texture) {
    const size = 8;
    const geometry = new THREE.BoxGeometry(size, size, size);
    const material = new THREE.MeshBasicMaterial({
      map: texture || filterTexture,
    });
    const mesh = new THREE.Mesh(geometry, material);
    mesh.scale.set(scale, scale, scale);
    return mesh;
  }

  function lowResCube(scale, pixelSize = 16) {
    const mesh = filterCube(scale);
    const renderTarget = new THREE.WebGLRenderTarget(1, 1, {
      magFilter: THREE.NearestFilter,
      minFilter: THREE.NearestFilter,
    });

    const planeScene = new THREE.Scene();

    const plane = new THREE.PlaneGeometry(1, 1);
    const planeMaterial = new THREE.MeshBasicMaterial({
      map: renderTarget.texture,
    });
    const planeMesh = new THREE.Mesh(plane, planeMaterial);
    planeScene.add(planeMesh);

    const planeCamera = new THREE.OrthographicCamera(0, 1, 0, 1, -1, 1);
    planeCamera.position.z = 1;

    return {
      obj3D: mesh,
      update(time, renderInfo) {
        const { width, height, scene, camera, renderer, pixelRatio } = renderInfo;
        const rtWidth = Math.ceil(width / pixelRatio / pixelSize);
        const rtHeight = Math.ceil(height / pixelRatio / pixelSize);
        renderTarget.setSize(rtWidth, rtHeight);

        camera.aspect = rtWidth / rtHeight;
        camera.updateProjectionMatrix();

        renderer.setRenderTarget(renderTarget);

        renderer.render(scene, camera);
        renderer.setRenderTarget(null);
      },
      render(renderInfo) {
        const { width, height, renderer, pixelRatio } = renderInfo;
        const viewWidth = width / pixelRatio / pixelSize;
        const viewHeight = height / pixelRatio / pixelSize;
        planeCamera.left = -viewWidth / 2;
        planeCamera.right = viewWidth / 2;
        planeCamera.top = viewHeight / 2;
        planeCamera.bottom = -viewHeight / 2;
        planeCamera.updateProjectionMatrix();

        // compute the difference between our renderTarget size
        // and the view size. The renderTarget is a multiple pixels magnified pixels
        // so for example if the view is 15 pixels wide and the magnified pixel size is 10
        // the renderTarget will be 20 pixels wide. We only want to display 15 of those 20
        // pixels so

        planeMesh.scale.set(renderTarget.width, renderTarget.height, 1);

        renderer.render(planeScene, planeCamera);
      },
    };
  }

  function createMip(level, numLevels, scale) {
    const u = level / numLevels;
    const size = 2 ** (numLevels - level - 1);
    const halfSize = Math.ceil(size / 2);
    const ctx = document.createElement('canvas').getContext('2d');
    ctx.canvas.width = size * scale;
    ctx.canvas.height = size * scale;
    ctx.scale(scale, scale);
    ctx.fillStyle = `hsl(${180 + u * 360 | 0},100%,20%)`;
    ctx.fillRect(0, 0, size, size);
    ctx.fillStyle = `hsl(${u * 360 | 0},100%,50%)`;
    ctx.fillRect(0, 0, halfSize, halfSize);
    ctx.fillRect(halfSize, halfSize, halfSize, halfSize);
    return ctx.canvas;
  }

  threejsLessonUtils.init({
    threejsOptions: {antialias: false},
  });
  threejsLessonUtils.addDiagrams({
    filterCube: {
      create() {
        return filterCube(1);
      },
    },
    filterCubeSmall: {
      create(info) {
        return lowResCube(.1, info.renderInfo.pixelRatio);
      },
    },
    filterCubeSmallLowRes: {
      create() {
        return lowResCube(1);
      },
    },
    filterCubeMagNearest: {
      async create() {
        const texture = await filterTexturePromise;
        const newTexture = texture.clone();
        newTexture.magFilter = THREE.NearestFilter;
        newTexture.needsUpdate = true;
        return filterCube(1, newTexture);
      },
    },
    filterCubeMagLinear: {
      async create() {
        const texture = await filterTexturePromise;
        const newTexture = texture.clone();
        newTexture.magFilter = THREE.LinearFilter;
        newTexture.needsUpdate = true;
        return filterCube(1, newTexture);
      },
    },
    filterModes: {
      async create(props) {
        const { scene, camera, renderInfo } = props;
        scene.background = new THREE.Color('black');
        camera.far = 150;
        const texture = await filterTexturePromise;
        const root = new THREE.Object3D();
        const depth = 50;
        const plane = new THREE.PlaneGeometry(1, depth);
        const mipmap = [];
        const numMips = 7;
        for (let i = 0; i < numMips; ++i) {
          mipmap.push(createMip(i, numMips, 1));
        }

        // Is this a design flaw in three.js?
        // AFAIK there's no way to clone a texture really
        // Textures can share an image and I guess deep down
        // if the image is the same they might share a WebGLTexture
        // but no checks for mipmaps I'm guessing. It seems like
        // they shouldn't be checking for same image, the should be
        // checking for same WebGLTexture. Given there is more than
        // WebGL to support maybe they need to abtract WebGLTexture to
        // PlatformTexture or something?

        const meshInfos = [
          { x: -1, y:  1, minFilter: THREE.NearestFilter,              magFilter: THREE.NearestFilter },
          { x:  0, y:  1, minFilter: THREE.LinearFilter,               magFilter: THREE.LinearFilter },
          { x:  1, y:  1, minFilter: THREE.NearestMipmapNearestFilter, magFilter: THREE.LinearFilter },
          { x: -1, y: -1, minFilter: THREE.NearestMipmapLinearFilter,  magFilter: THREE.LinearFilter },
          { x:  0, y: -1, minFilter: THREE.LinearMipmapNearestFilter,  magFilter: THREE.LinearFilter },
          { x:  1, y: -1, minFilter: THREE.LinearMipmapLinearFilter,   magFilter: THREE.LinearFilter },
        ].map((info) => {
          const copyTexture = texture.clone();
          copyTexture.minFilter = info.minFilter;
          copyTexture.magFilter = info.magFilter;
          copyTexture.wrapT = THREE.RepeatWrapping;
          copyTexture.repeat.y = depth;
          copyTexture.needsUpdate = true;

          const mipTexture = new THREE.CanvasTexture(mipmap[0]);
          mipTexture.mipmaps = mipmap;
          mipTexture.minFilter = info.minFilter;
          mipTexture.magFilter = info.magFilter;
          mipTexture.wrapT = THREE.RepeatWrapping;
          mipTexture.repeat.y = depth;

          const material = new THREE.MeshBasicMaterial({
            map: copyTexture,
          });

          const mesh = new THREE.Mesh(plane, material);
          mesh.rotation.x = Math.PI * .5 * info.y;
          mesh.position.x = info.x * 1.5;
          mesh.position.y = info.y;
          root.add(mesh);
          return {
            material,
            copyTexture,
            mipTexture,
          };
        });
        scene.add(root);

        renderInfo.elem.addEventListener('click', () => {
          for (const meshInfo of meshInfos) {
            const { material, copyTexture, mipTexture } = meshInfo;
            material.map = material.map === copyTexture ? mipTexture : copyTexture;
          }
        });

        return {
          update(time, renderInfo) {
            const {camera} = renderInfo;
            camera.position.y = Math.sin(time * .2) * .5;
          },
          trackball: false,
        };
      },
    },
  });

  const textureDiagrams = {
    differentColoredMips(parent) {
      const numMips = 7;
      for (let i = 0; i < numMips; ++i) {
        const elem = createMip(i, numMips, 4);
        elem.className = 'border';
        elem.style.margin = '1px';
        parent.appendChild(elem);
      }
    },
  };

  function createTextureDiagram(elem) {
    const name = elem.dataset.textureDiagram;
    const info = textureDiagrams[name];
    info(elem);
  }

  [...document.querySelectorAll('[data-texture-diagram]')].forEach(createTextureDiagram);
}