Modifier: add support for vertex groups

Allow blending the imported cache with the modifiers stack above the
MeshCache modifier.

This is particularly useful for instance when dealing with cloth
simulations performed in another software, where some parts of the cloth
are completely pinned (non-simulated, following the armature). Indeed,
this would allow modifying the animation in some areas without having to
rebake the other parts or the cloth, resulting in a much more flexible
workflow.

Reviewed By: #modeling, campbellbarton, mont29

Ref D9898

1 files changed, 65 insertions, 8 deletions

diff --git a/source/blender/modifiers/intern/MOD_meshcache.c b/source/blender/modifiers/intern/MOD_meshcache.c
index 6ef64ad8bc9..74f9887a973 100644
--- a/source/blender/modifiers/intern/MOD_meshcache.c
+++ b/source/blender/modifiers/intern/MOD_meshcache.c
@@ -36,8 +36,11 @@
 #include "DNA_screen_types.h"
 
 #include "BKE_context.h"
+#include "BKE_deform.h"
+#include "BKE_lib_id.h"
 #include "BKE_main.h"
 #include "BKE_mesh.h"
+#include "BKE_mesh_wrapper.h"
 #include "BKE_scene.h"
 #include "BKE_screen.h"
 
@@ -53,6 +56,7 @@
 #include "MOD_meshcache_util.h" /* utility functions */
 #include "MOD_modifiertypes.h"
 #include "MOD_ui_common.h"
+#include "MOD_util.h"
 
 static void initData(ModifierData *md)
 {
@@ -84,11 +88,16 @@ static bool isDisabled(const struct Scene *UNUSED(scene),
 static void meshcache_do(MeshCacheModifierData *mcmd,
                          Scene *scene,
                          Object *ob,
+                         Mesh *mesh,
                          float (*vertexCos_Real)[3],
                          int numVerts)
 {
   const bool use_factor = mcmd->factor < 1.0f;
-  float(*vertexCos_Store)[3] = (use_factor ||
+  int influence_group_index;
+  MDeformVert *dvert;
+  MOD_get_vgroup(ob, mesh, mcmd->defgrp_name, &dvert, &influence_group_index);
+
+  float(*vertexCos_Store)[3] = (use_factor || influence_group_index != -1 ||
                                 (mcmd->deform_mode == MOD_MESHCACHE_DEFORM_INTEGRATE)) ?
                                    MEM_malloc_arrayN(
                                        numVerts, sizeof(*vertexCos_Store), __func__) :
@@ -256,7 +265,29 @@ static void meshcache_do(MeshCacheModifierData *mcmd,
 
   if (vertexCos_Store) {
     if (ok) {
-      if (use_factor) {
+      if (influence_group_index != -1) {
+        const float global_factor = (mcmd->flag & MOD_MESHCACHE_INVERT_VERTEX_GROUP) ?
+                                        -mcmd->factor :
+                                        mcmd->factor;
+        const float global_offset = (mcmd->flag & MOD_MESHCACHE_INVERT_VERTEX_GROUP) ?
+                                        mcmd->factor :
+                                        0.0f;
+        if (mesh->dvert != NULL) {
+          for (int i = 0; i < numVerts; i++) {
+            /* For each vertex, compute its blending factor between the mesh cache (for `fac = 0`)
+             * and the former position of the vertex (for `fac = 1`). */
+            const MDeformVert *currentIndexDVert = dvert + i;
+            const float local_vertex_fac = global_offset +
+                                           BKE_defvert_find_weight(currentIndexDVert,
+                                                                   influence_group_index) *
+                                               global_factor;
+            interp_v3_v3v3(
+                vertexCos_Real[i], vertexCos_Real[i], vertexCos_Store[i], local_vertex_fac);
+          }
+        }
+      }
+      else if (use_factor) {
+        /* Influence_group_index is -1. */
         interp_vn_vn(*vertexCos_Real, *vertexCos_Store, mcmd->factor, numVerts * 3);
       }
       else {
@@ -270,34 +301,59 @@ static void meshcache_do(MeshCacheModifierData *mcmd,
 
 static void deformVerts(ModifierData *md,
                         const ModifierEvalContext *ctx,
-                        Mesh *UNUSED(mesh),
+                        Mesh *mesh,
                         float (*vertexCos)[3],
                         int numVerts)
 {
   MeshCacheModifierData *mcmd = (MeshCacheModifierData *)md;
   Scene *scene = DEG_get_evaluated_scene(ctx->depsgraph);
 
-  meshcache_do(mcmd, scene, ctx->object, vertexCos, numVerts);
+  Mesh *mesh_src = NULL;
+
+  if (ctx->object->type == OB_MESH && mcmd->defgrp_name[0] != '\0') {
+    /* `mesh_src` is only needed for vertex groups. */
+    mesh_src = MOD_deform_mesh_eval_get(ctx->object, NULL, mesh, NULL, numVerts, false, false);
+  }
+  meshcache_do(mcmd, scene, ctx->object, mesh_src, vertexCos, numVerts);
+
+  if (!ELEM(mesh_src, NULL, mesh)) {
+    BKE_id_free(NULL, mesh_src);
+  }
 }
 
 static void deformVertsEM(ModifierData *md,
                           const ModifierEvalContext *ctx,
-                          struct BMEditMesh *UNUSED(editData),
-                          Mesh *UNUSED(mesh),
+                          struct BMEditMesh *editData,
+                          Mesh *mesh,
                           float (*vertexCos)[3],
                           int numVerts)
 {
   MeshCacheModifierData *mcmd = (MeshCacheModifierData *)md;
   Scene *scene = DEG_get_evaluated_scene(ctx->depsgraph);
 
-  meshcache_do(mcmd, scene, ctx->object, vertexCos, numVerts);
+  Mesh *mesh_src = NULL;
+
+  if (ctx->object->type == OB_MESH && mcmd->defgrp_name[0] != '\0') {
+    /* `mesh_src` is only needed for vertex groups. */
+    mesh_src = MOD_deform_mesh_eval_get(ctx->object, editData, mesh, NULL, numVerts, false, false);
+  }
+  if (mesh_src != NULL) {
+    BKE_mesh_wrapper_ensure_mdata(mesh_src);
+  }
+
+  meshcache_do(mcmd, scene, ctx->object, mesh_src, vertexCos, numVerts);
+
+  if (!ELEM(mesh_src, NULL, mesh)) {
+    BKE_id_free(NULL, mesh_src);
+  }
 }
 
 static void panel_draw(const bContext *UNUSED(C), Panel *panel)
 {
   uiLayout *layout = panel->layout;
 
-  PointerRNA *ptr = modifier_panel_get_property_pointers(panel, NULL);
+  PointerRNA ob_ptr;
+  PointerRNA *ptr = modifier_panel_get_property_pointers(panel, &ob_ptr);
 
   uiLayoutSetPropSep(layout, true);
 
@@ -307,6 +363,7 @@ static void panel_draw(const bContext *UNUSED(C), Panel *panel)
   uiItemR(layout, ptr, "factor", UI_ITEM_R_SLIDER, NULL, ICON_NONE);
   uiItemR(layout, ptr, "deform_mode", 0, NULL, ICON_NONE);
   uiItemR(layout, ptr, "interpolation", 0, NULL, ICON_NONE);
+  modifier_vgroup_ui(layout, ptr, &ob_ptr, "vertex_group", "invert_vertex_group", NULL);
 
   modifier_panel_end(layout, ptr);
 }