I am loading a model with externally supplied matrices, those matrices are produced with a flipped Z-axis.

It’s because these models are designed with a Right-Handed coordinate system.

I have been multiplying a “mirror” matrix `Matrix.Scale(new Vector3(1,1,-1))`

to all matrices received but this is too slow during load time.

The obvious solution to me seems to be to modify the camera matrix (UNITY_MATRIX_VP in shaders).

Is this possible to do through the standard Unity Camera features or do I have to manually create my VP matrix and supply it in my shaders?