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, 2 insertions, 2 deletions

diff --git a/source/blender/depsgraph/intern/depsgraph_query_iter.cc b/source/blender/depsgraph/intern/depsgraph_query_iter.cc
index 171c9875e2a..2d2ee5dc4b4 100644
--- a/source/blender/depsgraph/intern/depsgraph_query_iter.cc
+++ b/source/blender/depsgraph/intern/depsgraph_query_iter.cc
@@ -153,10 +153,10 @@ bool deg_iterator_duplis_step(DEGObjectIterData *data)
     if (dob->no_draw) {
       continue;
     }
-    if (obd->type == OB_MBALL) {
+    if (dob->ob_data && GS(dob->ob_data->name) == ID_MB) {
       continue;
     }
-    if (deg_object_hide_original(data->eval_mode, dob->ob, dob)) {
+    if (obd->type != OB_MBALL && deg_object_hide_original(data->eval_mode, dob->ob, dob)) {
       continue;
     }