The support for fisheye cameras and other cameras with distortion.

[PeiLin-666]

In pyrender, users can choose 3 types of cameras model: PerspectiveCamera, OrthographicCamera and IntrinsicsCamera.
In IntrinsicsCamera, users can input the specific intrinsic parameters of camera.
But how can I input the distortion parameters? Because I want to render images from fisheye cameras. Thanks.