The precise way the clipper needs to be maintained may differ between APIs, so it is no longer owned by any render structure but instead HWDrawInfo only contains a reference.
For OpenGL there is still only one static clipper because without multithreaded BSP traversal there is no need for more.
Not only are they better placed in the common code, but they are also both per-viewpoint and not per-scene, so this is a far more suitable place and avoids saving and restoring them in the portal code.
I did not consider that this is an init-only option. So changing the CVAR may not affect game behavior at all. Instead its value must be moved to some globally accessible variable on startup that never gets changed again.
Game code should never ever call the renderer directly. This must be done through the video interface so that it can also work with other framebuffers later.
These files are not part of the actual renderer but part of the system code.
This means, for separated modern and legacy GL renderers, there still will only be one set of this, unlike everything else.
This is better be made part of the 2D interface.
That would have been done long ago if it hadn't been for the totally incompatible way this was handled by the purely paletted software renderer.
Now with that out of the way there is no point keeping this code this deeply embedded in the renderer.
Although this is currently safe there is no guarantee that future refactorings will keep the current draw lists, so it's better if GLDecal used its own copy of the data.
- precalculate if a sector's floor and ceiling plane overlap. This avoids rechecking this for each single call of hw_FakeFlat.
- vertices must be marked dirty every time they change after map setup. That means that ChangePlaneTexZ must do this as well, because it cannot rely on interpolation taking care of it.
- Having a 'dirty' argument for SetPlaneTexZ's ZScript version makes no sense. If the value changes from the script side the vertices must always be marked to be recalculated.
This was all over the place, with half of it using the function and half doing incomplete checks on the underlying variables.
Also did some optimization on the IGNOREHEIGHTSEC flag: Putting it on the destination sector instead of the model sector makes the check even simpler and allows to precalculate the effect of 3D floors on the heightsec, which previously had to be run on every call and made the function too complex for inlining.
* only call hw_CheckViewArea if the result is not known yet.
* check the map up front if it even contains heightsecs. This allows to shortcut the above check entirely for maps without sector transfers and will allow further optimizations.
Lots of this was still laid out for DirectDraw. This removes most of Begin2D so that it can be done more cleanlz.
Note that this commit renders weapon sprites and screen blends incorrectly. Those will be fixed in an upcoming commit.
Since they mess around with the texture coordinates, these need to be backed up and restored afterward.
There was also an issue with the ValidNormal check that was suffering from imprecisions that cause walls to be skipped, so the check was removed because it was mostly pointless.
