I believed the crash I experienced happened because:
1. The `extract_pos_nor_init` function is called.
2. Tasks are added to the task pool for `extract_pos_nor`.
3. The tasks begin to be executed while more tasks are added.
4. In some rare cases, all existing tasks are finished, but not all have been added yet.
5. This let the task-counter go down to zero.
6. This triggered a call to `extract_pos_nor_finish`.
7. Then more tasks are added and in the end `extract_pos_nor_finish` is called again.
A solution is to use a task pool that is suspended when created.
Unfortunately, there was an outdated comment, that was probably the root cause of the issue.
Reviewers: fclem, sergey
Differential Revision: https://developer.blender.org/D5680
Support for UV Stretching overlay during multi object editing. The
VBO now holds the ratios per fase. In the shader these ratios will
be compared against the global ratios. The global rations are created
from all selected objects.
The current implementation does not fit well with the draw module. The
plan is to move the drawing of other spaces towards the draw manager what
leads to a better fit. Currently the details on this solution is unclear
but this requirement will become an attentionpoint in the future design.
Reviewed By: fclem
Differential Revision: https://developer.blender.org/D5665
Calculating UV Stretching on large meshes showed garbage. The reason
is that the calculation is not thread save. Temporarily disable
threading for UV Stretching
This is done because they don't have the same update frequency. UV can be
persistent even on geometry update (ex: skinned object) but tangents
can change if the normals change.
Also the name buffer per vbo was too small to contain all names.
For clarity sake, the batch cache now uses exclusively per Loop attributes.
While this is a bit of a waste of VRAM (for the few case where per vert
attribs are enough) it reduces the complexity and amount of overall VBO
to update in general situations.
This patch also makes the VertexBuffers filling multithreaded. This make
the update of dense meshes a bit faster. The main bottleneck is the
IndexBuffers update which cannot be multithreaded efficiently (have to
increment a counter and/or do a final sorting pass).
We introduce the concept of "extract" functions/step.
All extract functions are executed in one thread each and if possible,
using multiple thread for looping over all elements.
Reviewed By: brecht
Differential Revision: http://developer.blender.org/D5424
