[12.0] Request to be able to enable GL_DEPTH_CLAMP

[Froyok]

Hi,

In my Love project, when rendering my meshes to use them as shadow volumes I rely on GL_DEPTH_CLAMP being enabled to avoid clipping triangles against the near plane. Without that it creates holes and break my shadows:

plane_intersection_shadow.mp4

Right now I enable this functionality by emitting manually a GL_ENABLE call, but that's not possible with the Vulkan backend for example. So it would be nice to be able to do so via Love API instead.

For more details on GL_DEPTH_CLAMP: https://paroj.github.io/gltut/Positioning/Tut05%20Depth%20Clamping.html

[Pikachuxxxx]

Hey! can I work on this?

So this is my plan:
Stage 1:

• Vulkan -> check depthClamp feature, set depthClampEnable = VK_TRUE/FALSE in VkPipelineRasterizationStateCreateInfo
• OpenGL -> glEnable/Disable(GL_DEPTH_CLAMP) (core >3.2 supports it by default ig)
• Metal -> https://developer.apple.com/documentation/metal/mtlrendercommandencoder/setdepthclipmode(_:)?language=objc can directly set on encoder when depth state changes?

Stage 2:

• Match depth ranges:
  • Vulkan/Metal [0,1] (default) and OpenGL [-1,1].
  • Could call glClipControl(GL_ZERO_TO_ONE) if we care about matching exactly with Vulkan and making it the default depth clip space of [0, 1].
• Not sure what love does it by default.

Stage 3:

• More Control: let users switch depth ranges themselves with glClipControl in GL and use VK_EXT_depth_clamp_control extension in VK.
• Metal Docs says we can do it in VS shader itself? the manual way...
• We can expose this via lua? SetDepthClampRange()? But the coverage for this extension is very less in vk so maybe not?

Still new to love so not sure how to expose this to lua, but from feature backend POV I hope this is acceptable?