three.js利用gpu选取物体并计算交点位置的方法示例(3)

6. gl_Position = projectionMatrix * modelViewMatrix * position
                      = projectionMatrix * camera.matrixWorldInverse * matrixWorld * position
                      = projectionMatrix * viewMatrix * modelMatrix * position

参考资料：

1. 完整实现代码：https://gitee.com/tengge1/ShadowEditor/blob/master/ShadowEditor.Web/src/event/GPUPickEvent.js

2. OpenGL中使用着色器绘制深度值：https://stackoverflow.com/questions/6408851/draw-the-depth-value-in-opengl-using-shaders

3. 在glsl中，获取真实的片元着色器深度值：https://gamedev.stackexchange.com/questions/93055/getting-the-real-fragment-depth-in-glsl