Blender Git Loki

Fix possible invalid normal use w/ tangent calc

Was using MFace normals, not MPoly

Merge branch 'master' into blender2.8

Alembic: Export mesh as mesh, even when it has no vertices.

This makes it possible to have an animated / procedurally generated mesh
that starts empty and obtains data in later frames.

Fixes the export of an empty mesh with an Ocean Modifier, as described in
issue T51351.

Alembic export: consider mesh with animation data as "animated"

This allows you to put any kind of animation data on the mesh, and its
shape will be exported on each timekey. Note that this timekey is unrelated
to the animation data (so we don't export on each keyframe, for example).

A practical example is the addition of an animated custom property to
trigger the export of animated mesh data. The mesh data can then be created
from any source, like Python scripts.

Not only is this useful in itself, it also provides a workaround for one
of the two issues described in T51351.

Alembic export: write Blender version to Alembic file

This is written in a custom metadata key, so it isn't shown by utilities
like abcecho or abcls. However, it's still something that's useful to
have available.

CMake: document that WITH_FFTW3 is also used for the ocean sim.

Fix T51586: Regression: Alembic containing animated curves / hair no longer working

Also fixed the same type of error when reading points.

Fix T51589: Principled Subsurface Scattering, wrong shadow color

Apply mix of subsurface and base color (wrt subsurface) for rays that
have transmitted the surface.

Move empty image drawing into its own pass

Cleanup: bmesh var naming

Fix leak in particle velocity global ramp

DwM: avoid indirect edit-mesh conversion

Storing edit-mesh data as indices for passing
only to get back edit-mesh data.

This also complicated checks for real edges in tessellation tris.

Simpler to pass data directly.

Fix error when duplicate GP object

When duplicate an object, the cache must be recalculated and is not copied.

Optimize particle primitive shader

Temp fix for vertex format with batch instancing

This prevents memory alignment from being screwed up when attributes are
optimized out in shader.

Implement particle velocity and acceleration visualization

Create a separated struct to hold shading groups

Merge branch 'master' into blender2.8

Fix T51534: Alembic: added support for face-varying vertex colours

Houdini writes vertex data in a different format than Blender does; Houdini
uses "face-varying scope", which means that the vertex colours are indexed
by an ever-increasing number over all vertices of all faces instead of the
vertex index.

I've also merged the read_custom_data_mcols() and read_mcols() functions,
because the latter was only called from the former, and the changes in this
commit would add yet more function parameters to pass.

Alembic: reduced code duplication in read_mcols()

A big chunk of code was copied between the if and else bodies. By using
a boolean to store whether the c3f_ptr or c4f_ptr should be used, the
in-loop condition is kept as simple as possible.