Encode glb file?

[bertt]

Hi, is there an option to encode using bytes from glb?

So this is possible:

var bytes = File.ReadAllBytes(file);
var opt = new DracoEncodeOptions();
var drcBytes = Draco.Encode(bytes, opt);

[lexchou-aspose]

Encode method turns a DracoMesh or DracoPointCloud instance into byte array, what you get in glb with draco compression is already byte array.

[javagl]

I just stumbled over this issue, and just in case that this is not considered to be resolved:

This issue is conceptually similar to openize-com/openize-drako-java#4 , even though it refers to the "opposite direction" (and a different language - these are details...).

This library for itself is unrelated to glTF. It does not know what glTF is. It can not read or write a glTF file. Abstractly, this library offers the functionalities to

• Read a byte array with draco data, decode it, and return the decoded mesh
• Take a mesh, encode it with draco, and return the result as a byte array

The question at this point is only "What is a mesh?". In the case of this library, it is a DracoMesh. In the case of glTF, a "mesh" is actually what is referred to as a mesh.primitive: Something that summarizes the geometry data, consisting of (optional) indices, and attributes like positions or normals.

The layer for integrating this library into a "glTF library" is relatively thin:

The snippet in the other issue already shows how this could be done for the decoding: The bufferView from the draco extension contains the draco data. This is passed to this library to obtain a DracoMesh. This draco mesh contains the attributes that will essentially be stored as the mesh.primitive.attributes of the decoded glTF, as accessor objects.

Similarly, encoding a glTF file into a draco-encoded file would consist of

• Taking the mesh.primitive.attribute accessor values
• Putting them into a DracoMesh
• Encoding this DracoMesh into a byte array using this library
• Storing the resulting byte array as a new bufferView
• Storing the structural information of that DracoMesh (including the buffer view index) as a Draco extension object in the mesh primitive

(This has to be done for each mesh primitive, of course)

This is a bit easier said than done. There are some tricky details: Which attributes can be encoded, and how? How to twiddle with these "attribute identifiers"? Things like vertex skinning or sparse accessors will require some thought.

But still, some openize-drako-net-glTF-encoder library (with some dependency to some existing .NET-based glTF library) could probably be implemented with a few hundred lines of code.