That was a nice and funny hunt, albeit rather time consumming!
To summarize, so far code was using a static global gpu_buffer for pbvh vbo drawing
of 'grid' types (multires mostly?).
There were two issues here:
1) Global gpu buffer was assigned to GPU_PBVH_Buffers->index_buf, but then nearly no
check was done when freeing that buffer, to ensure we were not freeing the global one
(not totally sure this one was actually causing any issue, but was bad and unsafe anyway).
Was solved by adding a flag to GPU_PBVH_Buffers to indicate when we are using some
'common' buffer here, which freeing is handled separately.
2) Main issue: if several multires objects in sculpt mode with different grid size
were present simultaneously, the global gpu buffer had to be resized for each object draw
(i.e., freed and re-allocated), but then the pbvh nodes from other objects storing freed reference
to that global buffer had no way to know that it had been freed, which was causing the segfault & crash.
Was solved by getting rid of that global buffer, and instead allocating one 'grid_commmon_gpu_buffer' per pbvh.
Told ya baby, globals are *PURE EVIL*!
This stores loop indices into the loop array giving easier acess
to data such as vertex-colors and UV's,
removing the need to store an MFace duplicate of custom-data.
This doesn't yet move all internal code from MFace to LoopTri just yet.
Only applies to:
- opengl drawing
- sculpting (pbvh)
- vertex/weight paint
Thanks to @psy-fi for review, fixes and improvements to drawing!
multires.
Code had special guards for such edges to stop this from happening. I
don't see why this is needed though since code above assigns smoothed
positions for all vertices in the grid.
After removing the guards I saw that this in fact was the only place
where grd adjacency was used, so I completely removed it.
Don't use a dedicated node layer but use temporary int layer instead.
Works like a charm as long as we are careful resetting the layer when
needed (after pbvh clearing and always after bmesh has been filled in
undo)
Tip by Campbell, thanks!
Located on topology panel.
To use just click on button and click on mesh.
Operator will just use the dimensions of the triangles below to set the
constant detail setting.
Also changed pair of scale/detail size with nice separate float
percentage value.
* Add BLI_pbvh_build_bmesh(), similar to the other PBVH builders but
specialized for BMesh. Whereas the PBVH leaf nodes for mesh and
grids only store a start-index and count into the primitive indices
array, the BMesh version uses GHashes to store the full set of faces
and vertices in leaf nodes
* Update PBVH iterator to handle BMesh
* Make some of the pbvh.c functions non-static so they can be used by
the new pbvh_bmesh code
* The BLI_pbvh_bmesh_update_topology() function is the main reason for
adding BMesh support to the PBVH. This function is used during a
sculpt stroke to dynamically collapse edges that are particular
short and subdivide edges that are particularly long.
* This doesn't make much difference for regular mesh/multires
sculpting, but for dynamic topology sculpting the undo stack isn't
split up by PBVH nodes, so it's more convenient to store the layer
data in PBVH nodes.
* Note that the life cycle of the layer displacement data is
unchanged -- it's only valid during a stroke with the layer brush,
gets free'd when the undo step ends.
