Blender Git Loki

Fix UI tooltips, layout, frame setting.

Fix NodetreeRef crashing due to null nodetree.

Merge branch 'master' into property-search-ui-v2

Added comment for not comparing in run-test and message

Merge branch 'master' into property-search-ui-v2

Merge branch 'master' into active-fcurve-keyframe

Context works in both NLA and graph editor

Merge branch 'master' into greasepencil-object

Merge branch 'master' into greasepencil-edit-curve

USD: remove library initialisation hack

Remove the hack for library initialisation; this is no longer necessary
as the required information can be passed to the USD library after its
static initialisers have run.

This means that USD's static initialisers will not be able to find the
USD plugin files. This is fine, as Blender now provides it with the
correct path before the first use of the library.

The removed hack was two-fold. It consisted of patching the USD library
to add a function, and calling that function from Blender. Now with that
function call removed from Blender's code, everything will keep working
regardless of whether the USD library is still patched or not. This'll
make bisecting things in the future a bit easier.

Manifest Task: https://developer.blender.org/T80320

USD: move library initialisation from `main()` to USD module

Initialize the USD library when used (instead of at startup), so that
this can happen inside the IO/USD module. This makes calls to the USD
library local to Blender's USD code.

Note that failure to find the USD JSON files will now only be reported
when the USD exporter is used, and not on every startup of Blender.

This is the first step in cleaning up the way Blender patches and
initialises the USD library.

Manifest Task: https://developer.blender.org/T80320

Move uv_indices in OBJMesh. Save some memory.

Since OBJMesh has dynamically allocated space in smooth groups
and uv_indices (which can be a lot), destruct objects that have
been written.

Use `const` at some places.

Use std::array, std::min, remove debug function.

Review update for D8753.

Hide Nurb from Writer. Rename OBJNurbs as per object type.

Render background when image isn't available

Merge branch 'master' into uvimage-editor-drawing

Merge branch 'master' into fcurve-modifier-panels

Remove export_params_ from OBJNurbs.

Remove export_params_ member from OBJMesh.

Not expose MPoly to writer. Write normals correctly

Write vertex normals only of smooth shaded polygons, otherwise
write face normals.

Keep normal indices in writer only since OBJMesh doesn't need to know
about export parameters. (will remove more such items from OBJMesh
later on.)

Keep MPoly related operations inside OBJMesh only & don't expose it to
Writer.

Review update: use float3, std::optional, c_str()

split nurbs function into two.

Add material name append if material groups are specified.