Take care of active output material node

Fix #1219 alpha only

From blender repo

Code for these will now skip over nodes used for wrapping.

They've been unified into a single f...

This also omits the texcoord when it is 0 (the default). Tests
were updated to be able to handle...

Teach the exporter to recognize using Sep/Math/Comb nodes to fake
wrap modes that an Image node ...

As suggested in #1113. CLIP is not supported by glTF, but clamping
seems better than repeating f...

Fix T82189

Revert "Fix T82189 empty primitives"

Fix T82189 empty primitives

This is not allowed in specification, but adding a check in order to
avoid traceback at import

Take care of active output material node

Doc: Add Clearcoat, Transmission, recent unlit changes.

numpy functions have replace the functions from this file.

Better filtering of exported nodes

Import: better error messages when loading files

Import: Set extras from mesh.

Also check the magic eariler, so we report the right error message
for files with length < 12.

This probably means the file is invalid.

This is done before converting to pydata since the format may
have changed between versions.

Fi...

Massage the error message a bit too.

Also cleaned up some comments.

It can just be a local variable.

Import/Export: fixes for material_index/material slots

Import: use bpy.utils.escape_identifier to escape names for action paths

Export: don't mess with normals when doing Apply Modifiers

This is the right way to do this. Fixes a bug for names with
non-latin characters that were esca...

Meshes with no materials in any primitive are just skipped; this
means all their polys have mate...

If material_index >= number of material slots, the old code would
export this as material: None....

Import: import grayscale emissiveFactor as Emission Strength

Also bump required Blender version since this was just added.

Export: support KHR_materials_unlit

There is no need to pass this to gather_material, it can do it
itself. (This is a remnant of 2.7...

Detects if a material has a "shadeless" graph and exports
with KHR_materials_unlit if it does.

...

Since KHR_materials_unlit is used whenever a Background socket is
found, these function (which a...

Groundwork for adding unlit support