It's not available in OpenGL ES and officially it's not supported on OpenGL 3.0/3.1.
Fallback to old depth range code if there is no method to disable depth clipping.
It's more important to have correct clipping than to have accurate depth values.
Inaccurate depth values can be fixed by slow depth.
In TimeSplitters: Future Perfect, PerfQuery is used to detect
the visibility of lights and draw coronas. 25 points are drawn
for each light. However, the returned count was incorrectly
being divided by four leading to dim coronas.
Using 4x antialiasing was a workaround because of a bug where
antialiasing multiplied the PerfQuery results. This commit
fixes that bug too (but only for OpenGL).
Note: It's not 100% perfect, as some of the GPU capablities leak into the
pixel shader UID.
Currently our UIDs don't get exported, so there is no issue. But someone
might want to fix this in the future.
As much as possible, the asserts have been moved out of the GetUID
function. But there are some places where asserts depend on variables
that aren't stored in the shader UID.
Using glMapBufferRange to read back the contents of the SSBO is extremely
slow on NVIDIA drivers. This is more noticeable at higher internal
resolutions. Using glGetBufferSubData instead does not seem to exhibit
this slowdown.
The D3D backend was always forcing Anisotropic filtering when that is enabled regardless of how the game chose to configure the texture filtering registers; this causes the same issues as "Force Filtering" without Anisotropy, such as causing game UI elements to no longer line up adjacent correctly. Historically, OpenGL's Anisotropy support has always worked "better" than D3D's due to seeming to not have this problem; unfortunately, OpenGL's Anisotropy specification only gives GL_LINEAR based filtering modes defined behavior, with only the mipmap setting being required to be considered. Some OpenGL implementations were implicitly disabling Anisotropy when the min/mag filters were set to GL_NEAREST, but this behavior is not required by the spec so cannot be relied on.
