[x3d-public] How to implement glTF EXT_mesh_gpu_instancing?!

[John Carlson]

Reminds me of:

https://coderextreme.net/X3DJSONLD/src/main/data/rubik.x3d

PROTOs of PROTOs of PROTOs

John

On Sun, Apr 21, 2024 at 6:36 AM Holger Seelig via x3d-public <
x3d-public at web3d.org> wrote:

> How to implement glTF EXT_mesh_gpu_instancing?!
>
> When looking through the glTF sample models, sooner or later you will
> stumble across an example and this extension.
>
>
> https://github.com/KhronosGroup/glTF/tree/main/extensions/2.0/Vendor/EXT_mesh_gpu_instancing
>
> https://github.com/KhronosGroup/glTF-Sample-Models/tree/main/2.0/SimpleInstancing
>
> The simplest idea to implement this, which I did, was to generate a lot of
> Transform nodes (one for each instance) and clone the shapes or geometry
> nodes. But this runs counter to the name of the extension (GPU). Especially
> if you create thousands of transform nodes for a shape with a geometry with
> only a few polygons. The extension is made to clone a lot of objects, e.g.
> a leaf on a tree, which then reappears in many places on the tree, only
> with different transformations, and everything should be calculated in one
> pass by the GPU.
>
> The second idea I had was to somehow incorporate the transformations
> (translation, rotation, scale) for each instance into the X3DGeometryNode
> nodes. However, this would have meant changing all of these nodes. So I
> discarded this for the time being and postponed it.
>
> Then I came up with the idea of why add it to the geometry nodes when you
> could invent a new shape node. So the idea of "InstancedShape" grew:
>
> Documentation of InstancedShape in X_ITE with example at the bottom of the
> page (2500 instances, 2,160,040 triangles):
> https://create3000.github.io/x_ite/components/x-ite/instancedshape/
>
> InstancedShape : X3DShapeNode {
>    # ... inherited fields
>    MFVec3f [in,out] translations [] #
>    MFRotation [in,out] rotations [] # list of rotations, one for each
> instance
>    MFVec3f [in,out] scales [] # list of scales, one for each instance
>    # List of translations, rotations, scales; one for each instance.
>    # If only one value is provided, it is provided to each instance
> equivalently.
> }
>
> The advantage is that the geometry nodes do not have to be changed, and
> the same functions could be used to implement these nodes that were already
> available for ParticleSystem nodes with some trivial additions.
>
> Examples to see InstancedShape node in action, all files are in glTF or
> GLB format converted to X3D:
>
> Simple Instancing (125 instances, 1,500 triangles):
>
> https://create3000.github.io/x_ite/playground/?url=https://raw.githubusercontent.com/KhronosGroup/glTF-Sample-Models/master/2.0/SimpleInstancing/glTF/SimpleInstancing.gltf
>
> Teapots Galore (958 instances, 7,725,314 triangles):
>
> https://create3000.github.io/x_ite/playground/?url=https://raw.githubusercontent.com/KhronosGroup/glTF/main/extensions/2.0/Vendor/EXT_mesh_gpu_instancing/samples/teapots_galore/teapots_galore.gltf
>
> Fur Instancing (10,000 instances, 3,200,000 triangles):
>
> https://create3000.github.io/x_ite/playground/?url=https://create3000.github.io/media/glTF/FurInstancing/FurInstancing.glb
>
> 3D Tiles (10 instances, 120 triangles):
>
> https://create3000.github.io/x_ite/playground/?url=https://raw.githubusercontent.com/CesiumGS/3d-tiles-samples/main/glTF/GpuInstancesMetadata/GpuInstancesMetadata.gltf
>
> Forest (100 instances, 21,400 triangles):
>
> https://create3000.github.io/x_ite/playground/?url=https://raw.githubusercontent.com/bertt/cesium_3dtiles_samples/master/samples/1.1/forest/forest.glb
>
> How do you do that, do you? Maybe we could consider this for a future X3D
> version.
>
> Make X3D even better!
> Best regards,
> Holger
>
> --
> Holger Seelig
> Leipzig, Germany
>
> holger.seelig at yahoo.de
> https://create3000.github.io/x_ite/
>
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