问题
I am beginner at GLSL. I was reading a vertex shader code and I don't understande this part of code:
out vec3 position;
...
gl_Position=gl_ModelViewProjectionMatrix*gl_Vertex;
position=vec3(gl_ModelViewMatrix*gl_Vertex);
What are the differences between gl_ModelViewProjectionMatrix and gl_ModelViewMatrix?
What are the differences between gl_Position and position?
回答1:
As you might suspect, gl_ModelViewProjectionMatrix is gl_ModelViewMatrix with the addition of the projection -- that is, the perspective camera distortion.
gl_Position is a predefined variable meaning "the projected result of this vertex shader" (all vertex shaders are required to assign a value to gl_Position), while the value "position" is an extra programmer-defined value that comes along for the ride (why is impossible to say, depends on the entire shader)
来源：https://stackoverflow.com/questions/15045562/gl-modelviewprojectionmatrix-vs-gl-modelviewmatrix