How to implement 3D cinema using three.js

This article mainly explains how to realize the functions and principle analysis of 3D cinema through three.js. Friends in need can refer to it.

In this article, we comprehensively analyze the basic knowledge of realizing 3D cinema by introducing the visual principles of 3D cinema and introducing the three.js event processing process.

1. Create a 3D space

You can imagine that we are in a room, and the room is a cube. If you have a taste for life, you may put wallpaper in the room, three.js You can easily create a cube and attach textures around it so that the camera is inside the cube and the camera can rotate 360 ​​degrees to simulate a real scene.

Convert to code:

const path = 'assets/image/'
 const format = '.jpg'
 const urls = [
 `${path}px${format}`, `${path}nx${format}`,
 `${path}py${format}`, `${path}ny${format}`,
 `${path}pz${format}`, `${path}nz${format}`
 ]
 const materials = []
 urls.forEach(url => {
 const textureLoader = new TextureLoader()
 textureLoader.setCrossOrigin(this.crossOrigin)
 const texture = textureLoader.load(url)
 materials.push(new MeshBasicMaterial({
 map: texture,
 overdraw: true,
 side: BackSide
 }))
 })
 const cube = new Mesh(new CubeGeometry(9000, 9000, 9000), new MeshFaceMaterial(materials))
 this.scene.add(cube)

CubeGeometry creates an oversized cube MeshFaceMaterial and attaches texture to the cube. Since the perspective is inside the cube, side: BackSide 2. Particle effect

A 3D model is composed of points, lines, and surfaces. You can traverse every point of the model, convert each point into a geometric model, and paste it with texture, copy the position of each point, and use these geometric models to recreate Forming a model with only points, this is the basic principle of particle effects.

this.points = new Group()
 const vertices = []
 let point
 const texture = new TextureLoader().load('assets/image/dot.png')
 geometry.vertices.forEach((o, i) => {
 // 记录每个点的位置
 vertices.push(o.clone())
 const _geometry = new Geometry()
 // 拿到当前点的位置
 const pos = vertices[i]
 _geometry.vertices.push(new Vector3())
 const color = new Color()
 color.r = Math.abs(Math.random() * 10)
 color.g = Math.abs(Math.random() * 10)
 color.b = Math.abs(Math.random() * 10)
 const material = new PointsMaterial({
 color,
 size: Math.random() * 4 + 2,
 map: texture,
 blending: AddEquation,
 depthTest: false,
 transparent: true
 })
 point = new Points(_geometry, material)
 point.position.copy(pos)
 this.points.add(point)
 })
 return this.points

new Group creates a group, which can be said to be a collection of particles. Set the particles and position through point.position.copy(pos). The coordinates are the same as the position of the corresponding point in the model 3. Click event processing

The click event of three.js requires the help of a ray caster (Raycaster). To facilitate understanding, please look at a picture first:

Raycaster emits a ray. intersectObject monitors the object hit by the ray

this.raycaster = new Raycaster()
// 把你要监听点击事件的物体用数组储存起来
this.seats.push(seat)

onTouchStart(event) {
 event.preventDefault()
 event.clientX = event.touches[0].clientX;
 event.clientY = event.touches[0].clientY;
 this.onClick(event)
 }

 onClick(event) {
 const mouse = new Vector2()
 mouse.x = ( event.clientX / this.renderer.domElement.clientWidth ) * 2 - 1
 mouse.y = - ( event.clientY / this.renderer.domElement.clientHeight ) * 2 + 1;
 this.raycaster.setFromCamera(mouse, this.camera)
 // 检测命中的座位
 const intersects = this.raycaster.intersectObjects(this.seats)
 if (intersects.length > 0) {
 intersects[0].object.material = new MeshLambertMaterial({
  color: 0xff0000
 })
 }
 }

intersects.length > 0 means that the ray hits a certain geometry. Lazy only implements click implementation on the mobile side. If you want to see how to implement it on PC, please see thee.js official website

4. Preliminary use of shaders

Shaders are divided into vertex shaders and fragment shaders. They are written in GLSL language. It is a language that communicates with the GPU. Here we only talk about how to use it.

const vertext = `
 void main()
 {
 gl_Position = projectionMatrix * modelViewMatrix * vec4(position,1.0);
 }
 `

const fragment = `
 uniform vec2 resolution;
 uniform float time;

 vec2 rand(vec2 pos)
 {
 return fract( 0.00005 * (pow(pos+2.0, pos.yx + 1.0) * 22222.0));
 }
 vec2 rand2(vec2 pos)
 {
 return rand(rand(pos));
 }

 float softnoise(vec2 pos, float scale)
 {
 vec2 smplpos = pos * scale;
 float c0 = rand2((floor(smplpos) + vec2(0.0, 0.0)) / scale).x;
 float c1 = rand2((floor(smplpos) + vec2(1.0, 0.0)) / scale).x;
 float c2 = rand2((floor(smplpos) + vec2(0.0, 1.0)) / scale).x;
 float c3 = rand2((floor(smplpos) + vec2(1.0, 1.0)) / scale).x;

 vec2 a = fract(smplpos);
 return mix(
 mix(c0, c1, smoothstep(0.0, 1.0, a.x)),
 mix(c2, c3, smoothstep(0.0, 1.0, a.x)),
 smoothstep(0.0, 1.0, a.y));
 }

 void main(void)
 {
 vec2 pos = gl_FragCoord.xy / resolution.y;
 pos.x += time * 0.1;
 float color = 0.0;
 float s = 1.0;
 for(int i = 0; i < 8; i++)
 {
 color += softnoise(pos+vec2(i)*0.02, s * 4.0) / s / 2.0;
 s *= 2.0;
 }
 gl_FragColor = vec4(color);
 }
 `
// 设置物体的质材为着色器质材
 let material = new ShaderMaterial({
 uniforms: uniforms,
 vertexShader: vertext,
 fragmentShader: fragment,
 transparent: true,
 })

5. Halo effect

Since it is a simulated cinema, I want to make a projector to simulate the light emitted by the projector.

// 光晕效果必须设置alpha = true
 const renderer = this.renderer = new WebGLRenderer({alpha: true, antialias: true})

 let textureFlare = new TextureLoader().load('assets/image/lensflare0.png')
 let textureFlare3 = new TextureLoader().load('assets/image/lensflare3.png')
 let flareColor = new Color(0xffffff)
 let lensFlare = new LensFlare(textureFlare, 150, 0.0 , AdditiveBlending, flareColor)
 lensFlare.add(textureFlare3, 60, 0.6, AdditiveBlending);
 lensFlare.add(textureFlare3, 70, 0.7, AdditiveBlending);
 lensFlare.add(textureFlare3, 120, 0.9, AdditiveBlending);
 lensFlare.add(textureFlare3, 70, 1.0, AdditiveBlending);
 lensFlare.position.set(0, 150, -85)

The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.

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