Blender Git Loki

OpenSubdiv: Only store edges topology for non-smooth edges

This change makes it so vertices of edge are only stored when edge
has non-zero crease. This allows to lower memory footprint of 1.5M
faces from 78 MiB to 54 MiB in the case all creases are zero.

Meshes with crease are more hard to predict due to array-based
storage, so it all depends on index of edge with crease. Worst case
(all edges are creased) still stays at 78 MiB.

OpenSubdiv: Allow any order of edge topology/sharpness assignment

Makes it possible to set adjacent vertices after edge sharpness.

Initially it seemed like useful sanity check, but with time it
became rather a burden.

OpenSubdiv: Optimize faces storage in mesh topology

Avoid per-face pointer and allocation: store everything as continuous
arrays.

Memory footprint for 1.5M faces:

- Theoretical worst case (all vertices and edges have crease) memory
goes down from 114 MiB to 96 MiB (15% improvement).

This case is not currently achievable since Blender does not expose
vertex crease yet.

- Current real life worst case (all edges have crease) memory goes
down from 108 MiB to 90 MiB (17% improvement).

- Best case (no creases at all) memory goes down from 96 MiB to 78 MiB
(19% improvement).

OpenSubdiv: Add regression tests for mesh topology

While this looks trivial it already allowed to catch issues in one
of previous attempt to optimize memory usage. It will totally be
useful for an upcoming refactor of face topology storage.

OpenSubdiv: Hide individual topology elements

Move all API to happen via MeshTopology.

This is a preparation for an upcoming memory optimization.

OpenSubdiv: Keep explicit storage of base mesh faces

Allows to perform comparison by doing linear comparison of indices.

Before cyclic match was used to deal with possibly changed winding from
OpenSubdiv side.

Speeds up comparison (and hence improves FPS), makes code more reliable
nut uses more memory.

OpenSubdiv: Add move semantic to the namespace

OpenSubdiv: Compare edge topology

This change makes it so topology refiner comparison will check vertices
of all existing/provided edges.

The initial claim that due to manifold nature of mesh there is no need
in "deep" edges check was wrong: some areas might only provide edges
with non-zero creases. So if crease of one edge goes changes from 1.0
to 0.0 and crease of other edge goes from 0.0 to 1.0 the old comparison
code would not have caught it.

OpenSubdiv: Cleanup, remove unused code

There is no need in edge map anymore.

OpenSubdiv: Refactor, move mesh topology comparison to own file

Makes it easier to follow and extend.

OpenSubdiv: Allow use of regular ordered map

OpenSubdiv: Move preliminary geometry counters check to mesh topology

OpenSubdiv: Add explicit storage for mesh topology

The idea is to use this explicit storage for topology comparison rather
than using base level. While this will have memory overhead it allows
to simplify comparison of such things as:

- Vertex sharpness (where base level from topology refiner will have it
refined, meaning it will be different from what application requested
for non-manifold and corner vertices).

- It will allow to simplify face-vertices comparison, where currently
O(N^2) algorithm is used due to possible difference in face winding.

- It will also allow to avoid comparison-time allocation of edge map.

Currently no functional changes, just preparing for development which
will happen next.

OpenSubdiv: Use explicit storage for edge sharpness

Similar to previous change in vertex sharpness, explicitly store value
provided by the converter.

Allows to avoid rather fragile check for boundary edges.

Also allows to avoid need in constructing edge map. This lowers memory
footprint of the comparison process and avoids memory allocations
during the comparison (which is an extra benefit from the performance
point of view).

OpenSubdiv: Add TODO avoid checking face-varying topology for equality

OpenSubdiv: Refactor, pass higher level object through comparison

OpenSubdiv: Refactor, move comparison to own file

OpenSubdiv: Compare sharpness based on converter

This change starts the transition of topology refiner comparison
to compare actual values given by the converter, which will not be
affected by the refinement or face winding synchronization steps.

Currently is only implemented for vertex sharpness, but will be
extended further as followup development.

Fixes T71908: Subdiv: Incorrect topology comparison, leading to poor performance

OpenSubdiv: Refactor creation of topology refiner

Consolidate it inside of the topology refiner implementation class,
which would allow to store extra data acquired during construction
of the OpenSubdiv's object.

OpenSubdiv: Refactor, move topology refiner factory to topology folder