THREE.js - 广告牌顶点着色器 [英] THREE.js - Billboard Vertex Shader

问题描述

我需要将 THREE.Mesh 的一个实例定向为始终面向相机.我知道我可以只使用 [THREE.Mesh].lookAt() 方法，但我正在尝试更多地处理我的 GLSL 切片，并希望能够在顶点着色器中执行此操作.

我已经通读了NeHe 的广告牌教程，这对我来说很有意义.好吧，除了将这些方向向量应用于每个顶点的位之外.

我觉得我已经非常接近完成这项工作了，但就目前而言，我的顶点着色器看起来更像是 90 年代的狂欢视频，而不是广告牌:

到目前为止的进展小提琴:http://jsfiddle.net/RZ4XE/2/>

下面是我的顶点着色器(片段着色器只分配了一个 vec4 颜色).它利用了 THREE.js 提供的各种默认统一/属性，下面列出，以防不熟悉 THREE.js 的人正在阅读:)

• cameraPosition (vec3),
• position(顶点位置，另一个vec3)，
• projectionMatrix(相机的projectionMatrix，mat4)，

• modelViewMatrix (camera.matrixWorldInverse * object.matrixWorld, mat4)

  void main() {vec3 look = normalize( cameraPosition - position );如果(长度(看)== 0.0){看.z = 1.0;}vec3 up = vec3( 0.0, 1.0, 0.0 );vec3 right = normalize( cross( up, look ) );up = normalize(cross(look, right));mat4 变换矩阵；变换矩阵[0][0] = right.x;变换矩阵[0][1] = right.y;变换矩阵[0][2] = right.z;变换矩阵[1][0] = up.x;变换矩阵[1][1] = up.y;变换矩阵[1][2] = up.z;变换矩阵[2][0] = look.x;变换矩阵[2][1] = look.y;变换矩阵[2][2] = look.z;gl_Position = 投影矩阵 * 模型视图矩阵 * 变换矩阵 * vec4(位置，1.0)；}

提前致谢.

解决方案

显然这有效:

gl_Position = projectionMatrix * (modelViewMatrix * vec4(0.0, 0.0, 0.0, 1.0) + vec4(position.x, position.y, 0.0, 0.0));

我实际上是想弄清楚如何制作轴对齐的广告牌.

I have the need to orientate an instance of THREE.Mesh to always face the camera. I know I could just use the [THREE.Mesh].lookAt() method, but I'm trying to work on my GLSL chops a bit more and want to be able to do this in a vertex shader.

I've read through NeHe's Billboarding tutorial, and it makes sense to me. Well, all apart from the bit where one applies these orientation vectors to each vertex.

I feel like I'm very close to getting this working, but as it stands at the moment, my vertex shader is looking more like a 90s rave video than a billboard:

Progress so far fiddle: http://jsfiddle.net/RZ4XE/2/

Below is my vertex shader (the fragment shader just assigns a vec4 color). It's making use of various default uniforms / attributes that THREE.js provides, listed below just in case someone unfamiliar with THREE.js is reading this :)

• cameraPosition (vec3),
• position (vertex position, another vec3),
• projectionMatrix (camera's projectionMatrix, mat4),

• modelViewMatrix (camera.matrixWorldInverse * object.matrixWorld, mat4)

  void main() {
  
      vec3 look = normalize( cameraPosition - position );
  
      if( length( look ) == 0.0 ) {
          look.z = 1.0;
      }
  
      vec3 up = vec3( 0.0, 1.0, 0.0 );
      vec3 right = normalize( cross( up, look ) );
      up = normalize( cross( look, right ) );
  
  
      mat4 transformMatrix;
  
      transformMatrix[0][0] = right.x;
      transformMatrix[0][1] = right.y;
      transformMatrix[0][2] = right.z;
  
      transformMatrix[1][0] = up.x;
      transformMatrix[1][1] = up.y;
      transformMatrix[1][2] = up.z;
  
      transformMatrix[2][0] = look.x;
      transformMatrix[2][1] = look.y;
      transformMatrix[2][2] = look.z;
  
      gl_Position = projectionMatrix * modelViewMatrix * transformMatrix * vec4( position, 1.0 );
  }
  

Thanks in advance.

解决方案

Apparently this works:

gl_Position = projectionMatrix * (modelViewMatrix * vec4(0.0, 0.0, 0.0, 1.0) + vec4(position.x, position.y, 0.0, 0.0));

I'm actually trying to figure out how to do axis aligned billboards.

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