[theschwa]

"How does “reflection” of the vase on the metal part of the table work, you might ask? The gaussians have “learned” the ages-old trick of duplicating and mirroring the geometry for reflection!"

Thank you! I'd seen people remove some of the SH coefficients while still getting reflections, and I couldn't understand how that worked. The old tricks sometimes really are the best tricks.

[contravariant]

Does make you wonder if you'd see a shadowy vase if you look at the table from below.

Although now that I think about it, there's no real reason to not just make the Gaussians invisible from behind.

[ReactiveJelly]

I think I've seen so in videos. Like someone dipping a camera underwater and the reflection is real splats.

But since the splats aren't a surface, they don't exactly have a "behind". They might render from every angle on purpose.

[BenoitP]

> But since the splats aren't a surface, they don't exactly have a "behind".

Spherical Harmonics apply to the whole sphere, splats can learn a SH color for their "behind". But by definition there is no data for these (no camera to tell what the color is). Nothing is preventing current pipelines to define that the opposite direction (splat looking at the camera) has a special color (black, zero-alpha, blend of blurred splats between camera and splat, etc); or to regularize all splats so that there is some amount of an "undefined" transparent component to be applied where camera won't define the SH.

[vanderZwan]

> Nothing is preventing current pipelines to define that the opposite direction (splat looking at the camera) has a special color (black, zero-alpha, blend of blurred splats between camera and splat, etc)

Wouldn't you need to know that there is no other camera view from the opposite direction? (sorry if dumb question, haven't actually looked at how GS are generated from input data)

[contravariant]

I can't be considered an expert either, but from what I understand they're currently using spherical harmonics (or some others set of basis functions) to model how a surface emits light from various directions.

However in most cases this will simply cut off as soon as you view a surface from the other side, so it kind of makes sense to add some special handling for that scenario. Especially since it can be hard to properly fit a discontinuity like that.

As it currently stands I imagine the reflection trick would be unable to work if you had a camera view from the other side, which is not ideal.

[vanderZwan]

Oh right, because if we're looking at (say) a ball from two sides, we're not looking at the same splat. So except for very thin 1D-approximating shapes like the spokes of a bike wheel, or pointy convex shapes, most splats will effectively be domes, right?