export material: new option to keep placeholders

Export: fix for texCoord/texture transform

Export: replace zero normals with UP

The primary_socket argument to gather_texture_info now tells it
what socket to get the texCoord/...

Zero normals are illegal in glTF.

I was not able to determine exactly why Blender generates zer...

This also exercises Apply Modifiers for the first time in test
suite I think.

Import/Perf: set fcurve interpolation using foreach_set

⚡️ Drastically improve performance when creating bufferViews by using…

Export: materials: support emission strength

Export: support use_nodes=False materials

Ignore Muted Material Nodes

This appears to no longer be necessary with the new normal exporting
code.

This let's you set up a test with the options you want to use
when exporting it, so tests can no...

Bump test version to 2.91

This is a linear multiplier to the emissiveFactor.

Fixes #571.

Docs: Mention requirements for sampling driver-controlled shape keys.

Export/Refactor: unify texture info functions

Export: detect when a file will be overwritten (#718)

Import: convert glTF meters to the units of the Blender scene

Refactor: delete fmt_char_dict/component_nb_dict

Export: store vertex colors as normalized ushorts

Import/Perf: ensure normalized accessors decode to float32s

Export: materials: export factors from MULTIPLY nodes

Update gltf2_blender_gltf2_exporter.py to allow for extensions in the asset node

Import: use action_group parameter to fcurves.new

Import: select all (and only) the imported objects

Permit missing texture.source

Export: always write texture samplers

Import/Perf: for "Use Normal Data", numpyify the code that guesses which polys are flat

Export/Perf: use numpy in extract_primitives (2-8x speedup)

Export: export material's "Alpha Hashed" blend mode as BLEND

Import: unlit: don't force opaque materials to HASHED blend mode

This previously exported as OPAQUE.

Contrary to the comment, all tests I did show this didn't do
anything.

The Normal/OcclusionTextureInfos were just copy-pasted from the
regular TextureInfo. They share ...

There was a comment about viewers not being able to handle missing
source. That should be enforc...

Adds get_factor from socket to read a factor from a socket directly
or from a MULTIPLY node in f...

Export KHR_materials_transmission.

Replace factory reset with select-all and delete.

For developers with custom system scripts folders, as described
in the DEBUGGING.md document, th...

Tests: don't check in validator reports

Mention shape key sampling requirements.

This is slightly simpler and faster.

These aren't used by extract_primitive anymore.

Import: enable KHR_mesh_quantization

Export: stopgap for zero-weight verts producing invalid files (#308)

Import: bugfix for primitives having different numbers of TEXCOORD_{n}s