three.js使用真实的3d模型来创建对象矩阵

这个方法能够获得比较高的3D真实感，但缺点是性能有限制。比如每个对象100个面（三角形）的话，那么1000个对象就需要渲染10万面，随着模型精度提升，将可能导致渲染性能问题。一个解决方法是把非重点的背景对象使用Sprite（2D贴图）来实现。

three, grid, performance

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JavaScript

编译

CSS

HTML

import * as THREE from '//techbrood.com/threejs/build/three.module.js';
import {OrbitControls} from '//techbrood.com/threejs/examples/jsm/controls/OrbitControls.js';

function main() {
  const canvas = document.querySelector('#c');
  const renderer = new THREE.WebGLRenderer({canvas});

const fov = 75;
  const aspect = 2;  // the canvas default
  const near = 0.1;
  const far = 1000;
  const camera = new THREE.PerspectiveCamera(fov, aspect, near, far);
  camera.position.set(0, 2, 5);

const controls = new OrbitControls(camera, canvas);
  controls.target.set(0, 2, 0);
  controls.minPolarAngle = 0;
  controls.maxPolarAngle = Math.PI / 2;
  controls.update();

const scene = new THREE.Scene();
  scene.background = new THREE.Color('lightblue');

function addLight(position) {
    const color = 0xFFFFFF;
    const intensity = 1;
    const light = new THREE.DirectionalLight(color, intensity);
    light.position.set(...position);
    scene.add(light);
    scene.add(light.target);
  }
  addLight([-3, 1, 1]);
  addLight([ 2, 1, .5]);

const trunkRadius = .2;
  const trunkHeight = 1;
  const trunkRadialSegments = 12;
  const trunkGeometry = new THREE.CylinderBufferGeometry(
      trunkRadius, trunkRadius, trunkHeight, trunkRadialSegments);

const topRadius = trunkRadius * 4;
  const topHeight = trunkHeight * 2;
  const topSegments = 12;
  const topGeometry = new THREE.ConeBufferGeometry(
      topRadius, topHeight, topSegments);

const trunkMaterial = new THREE.MeshPhongMaterial({color: 'brown'});
  const topMaterial = new THREE.MeshPhongMaterial({color: 'green'});

function makeTree(x, z) {
    const root = new THREE.Object3D();
    const trunk = new THREE.Mesh(trunkGeometry, trunkMaterial);
    trunk.position.y = trunkHeight / 2;
    root.add(trunk);

const top = new THREE.Mesh(topGeometry, topMaterial);
    top.position.y = trunkHeight + topHeight / 2;
    root.add(top);

root.position.set(x, 0, z);
    scene.add(root);

return root;
  }

for (let z = -50; z <= 50; z += 10) {
    for (let x = -50; x <= 50; x += 10) {
      makeTree(x, z);
    }
  }

// add ground
  {
    const size = 400;
    const geometry = new THREE.PlaneBufferGeometry(size, size);
    const material = new THREE.MeshPhongMaterial({color: 'gray'});
    const mesh = new THREE.Mesh(geometry, material);
    mesh.rotation.x = Math.PI * -0.5;
    scene.add(mesh);
  }

function resizeRendererToDisplaySize(renderer) {
    const canvas = renderer.domElement;
    const width = canvas.clientWidth;
    const height = canvas.clientHeight;
    const needResize = canvas.width !== width || canvas.height !== height;
    if (needResize) {
      renderer.setSize(width, height, false);
    }
    return needResize;
  }

function render() {
    if (resizeRendererToDisplaySize(renderer)) {
      const canvas = renderer.domElement;
      camera.aspect = canvas.clientWidth / canvas.clientHeight;
      camera.updateProjectionMatrix();
    }

renderer.render(scene, camera);

requestAnimationFrame(render);
  }

requestAnimationFrame(render);
}

main();

</script>

three, grid, performance

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