Divide by Depth for Instant 3D

Divide by Depth for Instant 3D(gabrieloc.com)

41 points by gabrieloc 2 days ago | 4 comments

aappleby 1 hour ago |

FWIW, if you start with "The view frustum is a 90 degree pyramid with the tip cut off at z = 1 and the 'end' at infinity", you can then work out how to map that to a NDC using a matrix and perspective divide.

I've used that when teaching short "Graphics 101" (not in the first session though) and the math comes out more intuitive than the usual "here's how to calculate a perspective matrix, don't ask where these numbers come from" version.

psvv 27 minutes ago | |

For me learning on my own, it was even illustrative to not use a near plane and see how things behind the camera would still appear in front of it.

A lot of 3D graphics can be derived pretty easily just from knowing a few basics like divide by depth. I think knowing how to construct a transformation matrix from a coordinate system basis is another one -- that would remove the need to look up how to construct a perspective matrix, for example.

A few things like that will get you pretty far and you can kind of take the same journey of discovery as early 3D pioneers. That's one of the best ways to learn because you're much more likely to remember something you figured out compared to something you just read about.

It gets tricky with perspective-correct textures, but running into issues like that on your own (even if not solved on your own) is part of the fun of learning, I think.

gabrieloc 2 days ago |

Hi! I wrote a few notes on how 3D cameras work with interactive examples to hopefully demystify a pretty complex topic that I once struggled with. Maybe this is useful for someone here, and if not, there are fun sliders to play with!

dyarosla 1 hour ago | |

The visuals and sliders are great!

Maybe consider clipping the ball properly on the edges of the sides of the view frustum ?

Similarly the near and far could also be clipped; i know this is not true of the math necessarily but is the expected result in 3d graphics applications.