Assert Loader (Texture and PBR) / Assert Manager

[DerKarlos]

For my project, 3D Rendering of OSM, I need this components.
For a good part, I have code solutions, but not in an asynchronous mode.
May be I could contribute to rend3, directly or as an example.
They also should run in the Web and all native platforms.

** The Assert Loader:
Load from Web or Filesystem. A Rust macro may switch 2 different path for Web and File.
Load user defined and Texture files
Inline "data:" should be detected and handled (solved in rand3)
Graphic Type ".svg" should be converted to bitmap (crates usvg,resvg)
I do not expect go have a "data: SVG" type, but it could be done to.

** Assert Manager:
A cache will avoid multiple loads. The "data:" may use a hashe-value.
Some kind of callback management will be needed

** PBR Loader:
Just a "high level" service. Takes a path and filenames for albedo etc.
Takes options like transparent

** My main problems are async!
Before I used a "step sequencer?"" called in the render cycle
and service workers for loading, decoding processing user files.
I still have to learn about Rust async.
In WASM, a worker may run via JavaScript interface or be in WASM, this year?

If I create a material, could the PBR files loaded asynchronously? The geometry get visible, colored only and the textures later?
Or would I get a callback if my user file or a texture is loaded to create the material and mesh?
Would any of this disturb the render cycle?

**
I will try to find existing functionalities in rand3. The gltf-loader may give some good help.
Any hints are welcome.

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