Cycles: add Fisheye Lens Polynomial camera model

This allows real world cameras to be modeled by specifying the coordinates of a
4th degree polynomial that relates a pixels distance (in mm) from the optical
center on the sensor to the angle (in radians) of the world ray that is
projected onto that pixel.

This is available as part of the panoramic lens type, however it can also be
used to model lens distortions in projective cameras for example.

Differential Revision: https://developer.blender.org/D12691

Cycles: add Fisheye Lens Polynomial camera model

This allows real world cameras to be modeled by specifying the coordinates of a
4th degree polynomial that relates a pixels distance (in mm) from the optical
center on the sensor to the angle (in radians) of the world ray that is
projected onto that pixel.

This is available as part of the panoramic lens type, however it can also be
used to model lens distortions in projective cameras for example.

Differential Revision: https://developer.blender.org/D12691