Fix T98813: crash with GPU subdiv in edit mode and instanced geometry

Instancing with geometry nodes uses just the evaluated Mesh, and ignores the
Object that it came from. That meant that it would try to look up the subsurf
modifier on the instancer object which does not have the subsurf modifier.

Instead of storing a session UUID and looking up the modifier data, store a
point to the subsurf modifier runtime data. Unlike the modifier data, this
runtime data is preserved across depsgraph CoW. It must be for the subdiv
descriptor contained in it to stay valid along with the draw cache.

As a bonus, this moves various Mesh_Runtime variables into the subsurf runtime
data, reducing memory usage for meshes not using subdivision surfaces.

Also fixes T98693, issues with subdivision level >= 8 due to integer overflow.

Differential Revision: https://developer.blender.org/D15184

1 files changed, 34 insertions, 28 deletions

diff --git a/source/blender/blenkernel/intern/subdiv_modifier.c b/source/blender/blenkernel/intern/subdiv_modifier.c
index e43da956ce5..f5423dccc0f 100644
--- a/source/blender/blenkernel/intern/subdiv_modifier.c
+++ b/source/blender/blenkernel/intern/subdiv_modifier.c
@@ -3,8 +3,6 @@
 
 #include "BKE_subdiv_modifier.h"
 
-#include "BLI_session_uuid.h"
-
 #include "MEM_guardedalloc.h"
 
 #include "DNA_mesh_types.h"
@@ -21,22 +19,40 @@
 
 #include "opensubdiv_capi.h"
 
-void BKE_subsurf_modifier_subdiv_settings_init(SubdivSettings *settings,
-                                               const SubsurfModifierData *smd,
-                                               const bool use_render_params)
+bool BKE_subsurf_modifier_runtime_init(SubsurfModifierData *smd, const bool use_render_params)
 {
   const int requested_levels = (use_render_params) ? smd->renderLevels : smd->levels;
 
-  settings->is_simple = (smd->subdivType == SUBSURF_TYPE_SIMPLE);
-  settings->is_adaptive = !(smd->flags & eSubsurfModifierFlag_UseRecursiveSubdivision);
-  settings->level = settings->is_simple ?
-                        1 :
-                        (settings->is_adaptive ? smd->quality : requested_levels);
-  settings->use_creases = (smd->flags & eSubsurfModifierFlag_UseCrease);
-  settings->vtx_boundary_interpolation = BKE_subdiv_vtx_boundary_interpolation_from_subsurf(
+  SubdivSettings settings;
+  settings.is_simple = (smd->subdivType == SUBSURF_TYPE_SIMPLE);
+  settings.is_adaptive = !(smd->flags & eSubsurfModifierFlag_UseRecursiveSubdivision);
+  settings.level = settings.is_simple ? 1 :
+                                        (settings.is_adaptive ? smd->quality : requested_levels);
+  settings.use_creases = (smd->flags & eSubsurfModifierFlag_UseCrease);
+  settings.vtx_boundary_interpolation = BKE_subdiv_vtx_boundary_interpolation_from_subsurf(
       smd->boundary_smooth);
-  settings->fvar_linear_interpolation = BKE_subdiv_fvar_interpolation_from_uv_smooth(
+  settings.fvar_linear_interpolation = BKE_subdiv_fvar_interpolation_from_uv_smooth(
       smd->uv_smooth);
+
+  SubsurfRuntimeData *runtime_data = (SubsurfRuntimeData *)smd->modifier.runtime;
+  if (settings.level == 0) {
+    /* Modifier is effectively disabled, but still update settings if runtime data
+     * was already allocated. */
+    if (runtime_data) {
+      runtime_data->settings = settings;
+    }
+
+    return false;
+  }
+  else {
+    /* Allocate runtime data if it did not exist yet. */
+    if (runtime_data == NULL) {
+      runtime_data = MEM_callocN(sizeof(*runtime_data), "subsurf runtime");
+      smd->modifier.runtime = runtime_data;
+    }
+    runtime_data->settings = settings;
+    return true;
+  }
 }
 
 static ModifierData *modifier_get_last_enabled_for_mode(const Scene *scene,
@@ -133,37 +149,27 @@ bool BKE_subsurf_modifier_can_do_gpu_subdiv(const Scene *scene,
 
 bool BKE_subsurf_modifier_has_gpu_subdiv(const Mesh *mesh)
 {
-  return BLI_session_uuid_is_generated(&mesh->runtime.subsurf_session_uuid);
+  SubsurfRuntimeData *runtime_data = mesh->runtime.subsurf_runtime_data;
+  return runtime_data && runtime_data->has_gpu_subdiv;
 }
 
 void (*BKE_subsurf_modifier_free_gpu_cache_cb)(Subdiv *subdiv) = NULL;
 
-Subdiv *BKE_subsurf_modifier_subdiv_descriptor_ensure(const SubsurfModifierData *smd,
-                                                      const SubdivSettings *subdiv_settings,
+Subdiv *BKE_subsurf_modifier_subdiv_descriptor_ensure(SubsurfRuntimeData *runtime_data,
                                                       const Mesh *mesh,
                                                       const bool for_draw_code)
 {
-  SubsurfRuntimeData *runtime_data = (SubsurfRuntimeData *)smd->modifier.runtime;
   if (runtime_data->subdiv && runtime_data->set_by_draw_code != for_draw_code) {
     BKE_subdiv_free(runtime_data->subdiv);
     runtime_data->subdiv = NULL;
   }
-  Subdiv *subdiv = BKE_subdiv_update_from_mesh(runtime_data->subdiv, subdiv_settings, mesh);
+  Subdiv *subdiv = BKE_subdiv_update_from_mesh(
+      runtime_data->subdiv, &runtime_data->settings, mesh);
   runtime_data->subdiv = subdiv;
   runtime_data->set_by_draw_code = for_draw_code;
   return subdiv;
 }
 
-SubsurfRuntimeData *BKE_subsurf_modifier_ensure_runtime(SubsurfModifierData *smd)
-{
-  SubsurfRuntimeData *runtime_data = (SubsurfRuntimeData *)smd->modifier.runtime;
-  if (runtime_data == NULL) {
-    runtime_data = MEM_callocN(sizeof(*runtime_data), "subsurf runtime");
-    smd->modifier.runtime = runtime_data;
-  }
-  return runtime_data;
-}
-
 int BKE_subsurf_modifier_eval_required_mode(bool is_final_render, bool is_edit_mode)
 {
   if (is_final_render) {