KHR_gaussian_splatting_compression_spz_2

[weegeekps]

This is a draft extension proposal for using Niantic Spatial's SPZ compression library for compression 3D Gaussian splatting data using the base KHR_gaussian_splatting extension with glTF. This extension targets version 2 of SPZ.

As we get closer to done with the base extension for 3D Gaussian splatting, KHR_gaussian_splatting, it has made more and more sense to break out the KHR_gaussian_splatting_compression_spz_2 extension for SPZ compression of 3DGS data. This allows them each to independently go through the ratification process and neither will hold up the other.

For previous history and conversations regarding the development of this extension, please look at the PR for KHR_gaussian_splatting before this linked comment.

[javagl]

The table formatting is broken

[javagl]

Not sure whether it's on the radar (I know that there currently is some turmoils around this topic...), but the wording and description around COLOR_0 may have to be updated.

This extension casually mentions COLOR_0, "as-if" it was a required attribute in the base extension. But in the base extension, it is described as an optional fallback. (I think that this means that there will be "fewer conversions" necessary, so in some way, it may actually simplify things, but the details should be reviewed carefully)

[weegeekps]

@javagl I have updates in progress that bring this in line with the current base spec including the changes around color spaces. I plan on pushing those changes as soon as that work is fully settled and we have consensus.