参考:
CesiumJS 源码杂谈 - 从光到 Uniform

渲染02-内置Uniform

1 Unifrom 的接口

路径: pacaages/engin/Source/Renderer/AutomaticUniforms.js

AutomaticUniforms 实际上是 Cesium 暴露给着色使用的接口集合。

AutomaticUniforms
  ┖ AutomaticUniform(czm_projection/czm_viewport/czm_viewportOrthographic...)

// AutomaticUniform包含:
czm_projection
czm_viewport
czm_viewportOrthographic
...

AutomaticUniforms = {
  czm_projection: new AutomaticUniform({
    size: 1,
    datatype: WebGLConstants.FLOAT_MAT4,
    getValue: function (uniformState) {
      return uniformState.projection;
    },
  })
}

2 Unifrom 的更新

内置unifrom实际上是 UniformState 负责更新。

路径: pacaages/engin/Source/Renderer/UniformState.js

类的从属关系:

Scene
  ┣ FrameState(_frameState)
      ┖ context
  ┖ Context(_context)
      ┖ UniformState(_us)

UniformState 更新的函数调用关系:

// Scene.js
fn render()
  UniformState.update();
    this.updateCamera();

3 Unifrom 的使用

同 DrawCommand 的执行。

简化版调用过程:

// Scene.js
fn render()
  // 1) 更新Uniform值
  UniformState.update();
    // 更新相机相关参数
    UniformState.updateCamera(camera);

  // 2) 执行命令
  DrawCommand.execute()
    // 使用 Uniform
    Contex.draw();

UniformState 关键成员:

czm_xxx 文档

来源	UniformState	cesium.js	说明	size	three.js
camera.viewMatrix	view3D	czm_view3D	世界转眼睛视图矩阵	4*4	viewMatrix
camera.viewMatrix	viewRotation3D	czm_viewRotation3D	视图矩阵的旋转部分	3*3	none
camera.viewMatrix	inverseView3D	czm_inverseView3D	眼睛转换为世界	4*4	none
frustum.projectionMatrix	projection	czm_projection	眼睛转剪裁投影矩阵	4*4	projectionMatrix
frustum.projectionMatrix	inverseProjection	czm_inverseProjection	剪裁转眼睛	4*4	none
view3D * _model	modelView3D	czm_modelView3D	模型视图矩阵	4*4	modelViewMatrix
todo	modelViewRelativeToEye	czm_modelViewRelativeToEye	todo	4*4	none
_projection * view3D	viewProjection	czm_viewProjection	视图投影矩阵	4*4	none