There are two issues revealed in the bug report:
- the GPU subdivision does not support meshes with only loose geometry
- the loose geometry is not subdivided
For the first case, checks are added to ensure we still fill the
buffers with loose geometry even if no polygons are present.
For the second case, this adds
`BKE_subdiv_mesh_interpolate_position_on_edge` which encapsulates the
loose vertex interpolation mechanism previously found in
`subdiv_mesh_vertex_of_loose_edge`.
The subdivided loose geometry is stored in a new specific data structure
`DRWSubdivLooseGeom` so as to not pollute `MeshExtractLooseGeom`. These
structures store the corresponding coarse element data, which will be
used for filling GPU buffers appropriately.
Differential Revision: https://developer.blender.org/D14171
A simple case of missing the tangent VBO. The tangents are computed from
the coarse mesh, and interpolated on the GPU for the final mesh. Code for
initializing the tangents, and the vertex format for the VBO was
factored out of the coarse extraction routine, to be shared with the
subdivision routine.
Reuse the same vertex normals calculation as for the GPU code, by
weighing each vertex normals by the angle of the edges incident to the
vertex on the face.
Additionally, remove limit normals, as the CPU code does not use them
either, and would also cause different shading issues when limit surface
is used.
Fixes T95242: shade smooth artifacts with edge crease and limit surface
Fixes T94919: subdivision, different shading between CPU and GPU
The issue has two causes: on one hand origin indices were not handled
properly, on the other hand the extraction type (Mesh, BMesh, or mapped)
was not detected correctly.
For the second case reuse the MeshRenderData creation from the coarse
code path so that we make the same decisions. Loose geometry extraction
had to be updated to properly handle the BMesh cases.
For the origin indices, in some cases (for edges and faces), the arrays
used by the subdivision code already have the origin indices baked into
them, so mapping them a second time through the origin index layer is
wrong, and could cause out of bounds accesses.
For vertices especially, we would use two arrays: one for mapping
subdivision vertices to coarse vertices, and another one to map coarse
vertices to subdivision loops used for the selection index buffer. The
second one is now removed (which saves a bit of memory) as it is did not
have the proper data setup for use with the origin indices and we can
easily compute it using the first array anyway.
The crash was happening when the mesh had loose edges.
Loose edges are not part of OpenSubdiv topology and hence should not be
communicated to the refiner. Pass ta boolean flag indicating whether an
edge is loose or not in the mesh foreach routines, which seems to be
the easiest way.
The evaluated mesh is a result of evaluated modifiers, and referencing
other evaluated IDs such as materials.
It can not be stored in the EditMesh structure which is intended to be
re-used by many areas. Such sharing was causing ownership errors causing
bugs like
T93855: Cycles crash with edit mode and simultaneous viewport and final render
The proposed solution is to store the evaluated edit mesh and its cage in
the object's runtime field. The motivation goes as following:
- It allows to avoid ownership problems like the ones in the linked report.
- Object level is chosen over mesh level is because the evaluated mesh
is affected by modifiers, which are on the object level.
This patch allows to have modifier stack of an object which shares mesh with
an object which is in edit mode to be properly taken into account (before
the change the modifier stack from the active object will be used for all
objects which share the mesh).
There is a change in the way how copy-on-write is handled in the edit mode to
allow proper state update when changing active scene (or having two windows
with different scenes). Previously, the copt-on-write would have been ignored
by skipping tagging CoW component. Now it is ignored from within the CoW
operation callback. This allows to update edit pointers for objects which are
not from the current depsgraph and where the edit_mesh was never assigned in
the case when the depsgraph was evaluated prior the active depsgraph.
There is no user level changes changes expected with the CoW handling changes:
should not affect on neither performance, nor memory consumption.
Tested scenarios:
- Various modifiers configurations of objects sharing mesh and be part of the
same scene.
- Steps from the reports: T93855, T82952, T77359
This also fixes T76609, T72733 and perhaps other reports.
Differential Revision: https://developer.blender.org/D13824
The point IBO should only have data for coarse vertices (or in general,
the vertices in the original mesh). As it used for displaying the
vertices for selection in edit mode, and as it indexes into the VBOs for
the positions and edit data, it is itself only indexed by coarse/
original vertex index.
For the subdivision case, this would allocate space for the final
subdivision vertex and reallocate to make room for loose geometry,
although only the first coarse vertex count amount of data would be.
Now just allocate for the required memory. Also reuse index buffer APIs
instead of doing manual work.
This adds vertex creasing support for OpenSubDiv for modeling, rendering,
Alembic and USD I/O.
For modeling, vertex creasing follows the edge creasing implementation with an
operator accessible through the Vertex menu in Edit Mode, and some parameter in
the properties panel. The option in the Subsurf and Multires to use edge
creasing also affects vertex creasing.
The vertex crease data is stored as a CustomData layer, unlike edge creases
which for now are stored in `MEdge`, but will in the future also be moved to
a `CustomData` layer. See comments for details on the difference in behavior
for the `CD_CREASE` layer between egdes and vertices.
For Cycles this adds sockets on the Mesh node to hold data about which vertices
are creased (one socket for the indices, one for the weigths).
Viewport rendering of vertex creasing reuses the same color scheme as for edges
and creased vertices are drawn bigger than uncreased vertices.
For Alembic and USD, vertex crease support follows the edge crease
implementation, they are always read, but only exported if a `Subsurf` modifier
is present on the Mesh.
Reviewed By: brecht, fclem, sergey, sybren, campbellbarton
Differential Revision: https://developer.blender.org/D10145
The crash is due to the fact that GPU subdivision extraction routines
for edit data (including UVs) only worked for BMesh. However, a Mesh
based version is still needed for texture painting. This adds the
missing components. This also ensures all data are properly initialized
(at least the ones revealed by the bug).
As described in T91186, this commit moves mesh vertex normals into a
contiguous array of float vectors in a custom data layer, how face
normals are currently stored.
The main interface is documented in `BKE_mesh.h`. Vertex and face
normals are now calculated on-demand and cached, retrieved with an
"ensure" function. Since the logical state of a mesh is now "has
normals when necessary", they can be retrieved from a `const` mesh.
The goal is to use on-demand calculation for all derived data, but
leave room for eager calculation for performance purposes (modifier
evaluation is threaded, but viewport data generation is not).
**Benefits**
This moves us closer to a SoA approach rather than the current AoS
paradigm. Accessing a contiguous `float3` is much more efficient than
retrieving data from a larger struct. The memory requirements for
accessing only normals or vertex locations are smaller, and at the
cost of more memory usage for just normals, they now don't have to
be converted between float and short, which also simplifies code
In the future, the remaining items can be removed from `MVert`,
leaving only `float3`, which has similar benefits (see T93602).
Removing the combination of derived and original data makes it
conceptually simpler to only calculate normals when necessary.
This is especially important now that we have more opportunities
for temporary meshes in geometry nodes.
**Performance**
In addition to the theoretical future performance improvements by
making `MVert == float3`, I've done some basic performance testing
on this patch directly. The data is fairly rough, but it gives an idea
about where things stand generally.
- Mesh line primitive 4m Verts: 1.16x faster (36 -> 31 ms),
showing that accessing just `MVert` is now more efficient.
- Spring Splash Screen: 1.03-1.06 -> 1.06-1.11 FPS, a very slight
change that at least shows there is no regression.
- Sprite Fright Snail Smoosh: 3.30-3.40 -> 3.42-3.50 FPS, a small
but observable speedup.
- Set Position Node with Scaled Normal: 1.36x faster (53 -> 39 ms),
shows that using normals in geometry nodes is faster.
- Normal Calculation 1.6m Vert Cube: 1.19x faster (25 -> 21 ms),
shows that calculating normals is slightly faster now.
- File Size of 1.6m Vert Cube: 1.03x smaller (214.7 -> 208.4 MB),
Normals are not saved in files, which can help with large meshes.
As for memory usage, it may be slightly more in some cases, but
I didn't observe any difference in the production files I tested.
**Tests**
Some modifiers and cycles test results need to be updated with this
commit, for two reasons:
- The subdivision surface modifier is not responsible for calculating
normals anymore. In master, the modifier creates different normals
than the result of the `Mesh` normal calculation, so this is a bug
fix.
- There are small differences in the results of some modifiers that
use normals because they are not converted to and from `short`
anymore.
**Future improvements**
- Remove `ModifierTypeInfo::dependsOnNormals`. Code in each modifier
already retrieves normals if they are needed anyway.
- Copy normals as part of a better CoW system for attributes.
- Make more areas use lazy instead of eager normal calculation.
- Remove `BKE_mesh_normals_tag_dirty` in more places since that is
now the default state of a new mesh.
- Possibly apply a similar change to derived face corner normals.
Differential Revision: https://developer.blender.org/D12770
This evaluator is used in order to evaluate subdivision at render time, allowing for
faster renders of meshes with a subdivision surface modifier placed at the last
position in the modifier list.
When evaluating the subsurf modifier, we detect whether we can delegate evaluation
to the draw code. If so, the subdivision is first evaluated on the GPU using our own
custom evaluator (only the coarse data needs to be initially sent to the GPU), then,
buffers for the final `MeshBufferCache` are filled on the GPU using a set of
compute shaders. However, some buffers are still filled on the CPU side, if doing so
on the GPU is impractical (e.g. the line adjacency buffer used for x-ray, whose
logic is hardly GPU compatible).
This is done at the mesh buffer extraction level so that the result can be readily used
in the various OpenGL engines, without having to write custom geometry or tesselation
shaders.
We use our own subdivision evaluation shaders, instead of OpenSubDiv's vanilla one, in
order to control the data layout, and interpolation. For example, we store vertex colors
as compressed 16-bit integers, while OpenSubDiv's default evaluator only work for float
types.
In order to still access the modified geometry on the CPU side, for use in modifiers
or transform operators, a dedicated wrapper type is added `MESH_WRAPPER_TYPE_SUBD`.
Subdivision will be lazily evaluated via `BKE_object_get_evaluated_mesh` which will
create such a wrapper if possible. If the final subdivision surface is not needed on
the CPU side, `BKE_object_get_evaluated_mesh_no_subsurf` should be used.
Enabling or disabling GPU subdivision can be done through the user preferences (under
Viewport -> Subdivision).
See patch description for benchmarks.
Reviewed By: campbellbarton, jbakker, fclem, brecht, #eevee_viewport
Differential Revision: https://developer.blender.org/D12406
