Feature
Gaussian splat data sets are usually generated by reconstructing the splats from a set of photos. The result inevitably includes points/splats that may not be part of the actual object of interest. For example, when capturing a building from a drone scan, then the data set will contain splats that have been reconstructed from the surrounding environment or from the sky:
There are different options for where, when, and how different forms of "clipping" could happen. The main categories are whether it happens before or after the tiling process.
Option 1: Preprocessing
This is, strictly speaking, not an option that can be implemented sensibly in CesiumJS itself. But if a Gaussian splat tileset is not generated with a photo reconstruction, but from a PLY file, then it is possible to use online editors like https://superspl.at/editor to edit the PLY file manually, before tiling:
Option 2: Postprocessing
For existing Gaussian splat tilesets (regardless of whether they have been created with a reconstruction process, or from a PLY file), there is no appropriate tooling for clipping. This clipping would have to happen on the level of the whole tileset. Specifically: The clipping would have to take the LOD hierarchy into account, clip the splat data sets for every LOD, and write out the result. (Or... exactly not write out whatever has been completely clipped away).
(I have some local tooling for stuff like this, and a basic form of that could easily - nearly trivially - be implemented as part of the 3D Tiles Tools. But depending on the exact requirements (e.g. the actual clipping shape, and how it is defined), a more interactive solution would be desirable).
Option 3: Runtime clipping
Regardless of whether tiling happens based on photo reconstruction or based on PLY data, and regardless of where any clipping of the data already happened, it should always be possible to apply the standard clipping mechanisms of CesiumJS to existing tilesets. This includes clipping planes and clipping polygons, and preferably additional, more powerful clipping functionalities (namely, clipping volumes).
There are some structures that could either be used for implementing this functionality, or that could be seen as "workarounds" for the current state. The following is an example sandcastle that will not show the desired effect on the sandcastle that is currently depoloyed, but it will work once #13418 is merged: It uses a custom shader to cut away parts of a splat data set:
https://sandcastle.cesium.com/index.html#c=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
It defines a custom shader that simply discards all fragments when their distance to the center of the bounding sphere of the tileset is larger than a user-selected threshold:
This could be extended arbitrarily (i.e. to define clipping planes or volumes), but can be seen as a "proof of concept" for now.
AI acknowledgment
Feature
Gaussian splat data sets are usually generated by reconstructing the splats from a set of photos. The result inevitably includes points/splats that may not be part of the actual object of interest. For example, when capturing a building from a drone scan, then the data set will contain splats that have been reconstructed from the surrounding environment or from the sky:
There are different options for where, when, and how different forms of "clipping" could happen. The main categories are whether it happens before or after the tiling process.
Option 1: Preprocessing
This is, strictly speaking, not an option that can be implemented sensibly in CesiumJS itself. But if a Gaussian splat tileset is not generated with a photo reconstruction, but from a PLY file, then it is possible to use online editors like https://superspl.at/editor to edit the PLY file manually, before tiling:
Option 2: Postprocessing
For existing Gaussian splat tilesets (regardless of whether they have been created with a reconstruction process, or from a PLY file), there is no appropriate tooling for clipping. This clipping would have to happen on the level of the whole tileset. Specifically: The clipping would have to take the LOD hierarchy into account, clip the splat data sets for every LOD, and write out the result. (Or... exactly not write out whatever has been completely clipped away).
(I have some local tooling for stuff like this, and a basic form of that could easily - nearly trivially - be implemented as part of the 3D Tiles Tools. But depending on the exact requirements (e.g. the actual clipping shape, and how it is defined), a more interactive solution would be desirable).
Option 3: Runtime clipping
Regardless of whether tiling happens based on photo reconstruction or based on PLY data, and regardless of where any clipping of the data already happened, it should always be possible to apply the standard clipping mechanisms of CesiumJS to existing tilesets. This includes clipping planes and clipping polygons, and preferably additional, more powerful clipping functionalities (namely, clipping volumes).
There are some structures that could either be used for implementing this functionality, or that could be seen as "workarounds" for the current state. The following is an example sandcastle that will not show the desired effect on the sandcastle that is currently depoloyed, but it will work once #13418 is merged: It uses a custom shader to cut away parts of a splat data set:
https://sandcastle.cesium.com/index.html#c=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
It defines a custom shader that simply discards all fragments when their distance to the center of the bounding sphere of the tileset is larger than a user-selected threshold:
This could be extended arbitrarily (i.e. to define clipping planes or volumes), but can be seen as a "proof of concept" for now.
AI acknowledgment