Hacker News Reader

Comment by etskinner | Hacker News Reader

How does it capture the reflection (the iridescence of the fly's body)? It's almost as if I can see the background through the reflection.

I would have thought that since that reflection has a different color in different directions, gaussian splat generation would have a hard time coming to a solution that satisfies all of the rays. Or at the very least, that a reflective surface would turn out muddy rather than properly reflective-looking.

Is there some clever trickery that's happening here, or am I misunderstanding something about gaussian splats?

View on HN

The color is view-dependent, which also means the lighting is baked in and results in them not being usable directly for 3D animation/environments (though I’m sure there must be research happening on dynamic lighting).

Sometimes it will “go wrong”, you can see in some of the fly models that if you get too close, body parts start looking a bit transparent as some of the specular highlights are actually splats on the back of an internal surface. This is very evident with mirrors - they are just an inverted projection which you can walk right into.

Feels like there must be some way to use "variability of colour by viewing angle" for tiny clusters of volumes in the object as a way to generate material settings when converting the Gaussian splat model to a traditional 3D model.

E.g. if you have a cluster of tiny adjacent volumes that have high variability based on viewing angle, but the difference between each of those volumes is small, handle it as a smooth, reflective surface, like chrome.

You can’t easily convert a gaussian splat to a polygon based model, the representation through blurry splats is the breakthrough.

Gaussian splats can have colour components that depend on the viewing direction. As far as I know, they are implemented as spherical harmonics. The angular resolution is determined by the number of spherical harmonic components. If this is too low, all reflection changes will be slow and smooth, and any reflection will be blurred.

FTA, "A Gaussian splat is essentially a bunch of blurry ellipsoids. Each one has a view-dependent color". Does that explain it?

See the section titled "View-dependant colors with SH" here: https://towardsdatascience.com/a-comprehensive-overview-of-g...

Reply on news.ycombinator.com