EXT_implicit_ellipsoid_region Proposal

[j9liu]

This extension proposal builds on top of KHR_implicit_shapes (#2370) to enable the definition of implicit ellipsoid-based regions. This is useful in geospatial applications where regions are defined in longitude / latitude / height coordinates relative to an ellipsoid model, e.g., the WGS84 ellipsoid.

This enables the rendering of ellipsoid-conforming voxels in EXT_primitive_voxels (#2496), allowing larger regions of data to follow the ellipsoid's surface more closely and improve the real-world accuracy of the data over uniform box voxels.

[aaronfranke]

The EXT prefix is reserved for multi-vendor extensions. Which vendors besides Cesium have worked on this?

[javagl]

Multiple vendors working on a specific extension is not (or no longer) a strict requirement for the EXT_ prefix. The informal meaning of that prefix is rather something like the vendor ~"not claiming the (naming) rights".
(Most of the open extension PRs are using the EXT_ prefix, FWIW. The exceptions are mainly the KHR_ ones, which is not much more than the "Khronos vendor prefix" nowadays)

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