Metaball: Evaluate metaball objects as mesh components

With the ultimate goal of simplifying drawing and evaluation,
this patch makes the following changes and removes code:
- Use `Mesh` instead of `DispList` for evaluated basis metaballs.
- Remove all `DispList` drawing code, which is now unused.
- Simplify code that converts evaluated metaballs to meshes.
- Store the evaluated mesh in the evaluated geometry set.

This has the following indirect benefits:
- Evaluated meshes from metaball objects can be used in geometry nodes.
- Renderers can ignore evaluated metaball objects completely
- Cycles rendering no longer has to convert to mesh from `DispList`.
- We get closer to removing `DispList` completely.
- Optimizations to mesh rendering will also apply to metaball objects.

The vertex normals on the evaluated mesh are technically invalid;
the regular calculation wouldn't reproduce them. Metaball objects
don't support modifiers though, so it shouldn't be a problem.
Eventually we can support per-vertex custom normals (T93551).

Differential Revision: https://developer.blender.org/D14593

1 files changed, 4 insertions, 4 deletions

diff --git a/source/blender/blenkernel/BKE_mball_tessellate.h b/source/blender/blenkernel/BKE_mball_tessellate.h
index 2dc16dc64d6..0840c51bb4d 100644
--- a/source/blender/blenkernel/BKE_mball_tessellate.h
+++ b/source/blender/blenkernel/BKE_mball_tessellate.h
@@ -12,11 +12,11 @@ extern "C" {
 struct Depsgraph;
 struct Object;
 struct Scene;
+struct Mesh;
 
-void BKE_mball_polygonize(struct Depsgraph *depsgraph,
-                          struct Scene *scene,
-                          struct Object *ob,
-                          struct ListBase *dispbase);
+struct Mesh *BKE_mball_polygonize(struct Depsgraph *depsgraph,
+                                  struct Scene *scene,
+                                  struct Object *ob);
 
 void BKE_mball_cubeTable_free(void);