[SOLVED] What does the second parameter on GL.GetGPUProjectionMatrix mean

[litefeel]

Hi. Every one.

I am calculating UNITY_MATRIX_P myself.

var projection = Camera.main.projectionMatrix;
projection = GL.GetGPUProjectionMatrix(projection, true);

the proj is same of UNITY_MATRIX_P in shader.

Unity - Scripting API: GL.GetGPUProjectionMatrix

public static Matrix4x4 GetGPUProjectionMatrix(Matrix4x4 proj, bool renderIntoTexture);

renderIntoTexture Will this projection be used for rendering into a RenderTexture?

The renderIntoTexture value should be set to true if you intend to render into a RenderTexture with this projection matrix. On some platforms it affects how the final matrix will look like.

I always set the second parameter to true. But when do I need to set it to false?

Update：
Yes， the second param is renderIntoTexture.
If the Allow MSAA is checked, then the camera also render to the texture.
This option is selected by default in new scenes.

[Tartiflette]

I think it’s because on some graphics API (maybe dx9 and earlier?) the y texture coordinate is inverted compared to the screen coordinate. Which means that you have to compensate that by inverting something in the projection matrix, which is what this parameter does when needed.
I reckon you will never need to not use it unless you plan on rendering straight to the screen.