This was done to clean up the license and to ensure that any commercial fork of the engine has to obey the far stricter requirements concerning source distribution. The old license was compatible with GPLv2 whereas combining GPLv2 and LGPLv3 force a license upgrade to GPLv3. The license of code that originates from ZDoomGL has not been changed.
This is slower than doing it in the render pass so it's only active when actually needed - it's also slower than using a client array so this code only gets used when there is no choice but to work with a 3.x core profile context.
It makes no sense having them organized differently in this struct than what the rendering code needs. This saves one redundant copy operation and a function-local static variable.
This method has the advantage that it also works for models, xy-billboarded sprites and walls that require complex splitting of the polygon. The old method using actual polygon splitting only works for strictly vertical data that could be trivially split in two.
- avoid rebinding the same texture multiple times, as there's considerable overhead in the texture manager.
- check gl_sort_textures only once per scene, not per draw list.
- use sampler objects to avoid creating up to 4 different system textures for one game texture just because of different clamping settings.
- avoids flushing all textures for change of texture filter mode.
- separate sprite and regular dimensions on the material level to have better control over which one gets used. It's now an explicit parameter of ValidateTexture. The main reason for this change is better handling of wall sprites which may not be subjected to such handling.
- create mipmaps based on use case, not texture type.
- allows removal of FCloneTexture hack for proper sharing of the same sprite for decals and other purposes.
- better precaching of skyboxes.
- added a light preprocessing pass to the renderer so that a non-persistent buffer can be used with minimal mapping/unmapping. This only gets used if necessary because it adds some overhead to the renderer.
