This allows to use unions on the C++ side and safe type
casting on the GPU side.
The type casting functions are statically verified at
compile time in C++.
This PR doesn't change the size of the light struct
but removes the need of packing floats in the `object_mat`.
The matrix will be changed to a `float4x3` in another PR
and will reduce the struct by 16 bytes.
This remove the need for the light parameters macros and
reveals the padding members that could be used for future
features for each type.
After this, all accesses to light type dependent data in
the shaders should be done using:
- `LightLocalData light_local_data_get(LightData light)`
- `LightSpotData light_spot_data_get(LightData light)`
- `LightAreaData light_area_data_get(LightData light)`
- `LightSunData light_sun_data_get(LightData light)`
Note that these functions are simple passthrough for Metal
since it supports `union` (but enforce for error checking
if option is enabled).
The error check on GPU is a bit costly so it is disabled
by default.
Pull Request: https://projects.blender.org/blender/blender/pulls/119713
4d502ab51d