Supporting orthographic projection

[jakeoung]

Thanks for making this amazing repo!

I just wonder if this code can support orthographic projection, instead of perspective projection.

[oliver-batchelor]

Yes! This is exactly why I wanted another implementation to make it easy to support this kind of thing.

It's a matter of adding a replacement project_to_image for the orthographic projection (and adding a different frustum culling).

It should be simpler than perspective projection because there's no need to approximate the projection (it's just the xy components of the transformed covariance matrix).

I'll give it a try in a few days (unless you beat me to it) as it could be useful to show how to use different projections.

[iamblitzcrank]

Nice work! If so, is there a way to enable equi-rectangular projection?

[oliver-batchelor]

@iamblitzcrank Do you have any background on how to project the gaussian using equirectangular projection? In particular the covariance mapping for 3D to 2D.

For perspective projection this (approximation) is described in
Object Space EWA Surface Splatting

But for equirectangular projection, it would be quite different.

I haven't gotten very far with adding different projections, but my idea in terms of implementing it is to have an abstract CameraParams class (currently there is one but it is only perspective) with an overloaded projection function which calls a custom kernel. Happy if anyone wants to contribute here!!

[oliver-batchelor]

There seems to be a paper on this recently published
"360-GS: Layout-guided Panoramic Gaussian Splatting For Indoor
Roaming"

Equations 4-10 gives exactly the necessary transformation.

[yh-yoon]

Thanks for your response, I'll check about it.