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Comment by bob1029 | Hacker News Reader

> clipping against the near plane (hopefully rare in practice)

I am not sure I understand why this would be rare. If I am intending to construct a rasterizer for a first-person shooter, clipping is essentially mandatory for all but the most trivial of camera arrangements.

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Yes, of course, I was definitely imagining you were struggling to get simpler scenes to work. But also, proportionally few of your triangles in any given scene should be near-plane clipped. It's OK to have a slow path for it, and then speed it up later. I've never felt the math for the adjusted barycentrics is too hard, but it can take a bit to wrap your head around. Good luck :)

You and the GP have different rasterization algorithms in mind I think. The GP, I presume, is talking about a classic scanline-based rasterizer rather than an edge function "am I inside or not" type rasterizer that GPUs use.

Clipping or culling? I expect it’s mostly the latter unless your camera ends up intersecting the geometry.

Both. You almost always need both.

Clipping deals with geometry that is partially inside the camera. Culling (either for backfaces or entire instances) is a preliminary performance optimization that can be performed in a variety of ways.

As an example, if you're writing a shooter then the floor might be a large square that will almost definitely be intersecting the near plane. You absolutely need clipping here.

This is precisely the first place I realized I needed proper clipping. Wasted many hours trying to hack my way out of doing it the right way.

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