source/blender/blenkernel/BKE_grease_pencil.hh

@@ -706,6 +706,7 @@ TREENODE_COMMON_METHODS_FORWARD_IMPL(LayerGroup);
 namespace convert {
 
 void legacy_gpencil_frame_to_grease_pencil_drawing(const bGPDframe &gpf,
+                                                   const ListBase &vertex_group_names,
                                                    GreasePencilDrawing &r_drawing);
 void legacy_gpencil_to_grease_pencil(Main &main, GreasePencil &grease_pencil, bGPdata &gpd);
 

source/blender/blenkernel/intern/grease_pencil_convert_legacy.cc

@@ -8,6 +8,7 @@
 
 #include "BKE_attribute.hh"
 #include "BKE_curves.hh"
+#include "BKE_deform.hh"
 #include "BKE_grease_pencil.hh"
 #include "BKE_material.h"
 
@@ -19,10 +20,52 @@
 
 #include "DNA_gpencil_legacy_types.h"
 #include "DNA_grease_pencil_types.h"
+#include "DNA_meshdata_types.h"
 
 namespace blender::bke::greasepencil::convert {
 
+/**
+ * Find vertex groups that have assigned vertices in this drawing.
+ * Returns:
+ * - ListBase with used vertex group names (bDeformGroup)
+ * - Array of indices in the new vertex group list for remapping
+ */
+static void find_used_vertex_groups(const bGPDframe &gpf,
+                                    const ListBase &all_names,
+                                    ListBase &r_vertex_group_names,
+                                    Array<int> &r_indices)
+{
+  const int num_vertex_groups = BLI_listbase_count(&all_names);
+  Array<int> is_group_used(num_vertex_groups, false);
+  LISTBASE_FOREACH (bGPDstroke *, gps, &gpf.strokes) {
+    if (!gps->dvert) {
+      continue;
+    }
+    Span<MDeformVert> dverts = {gps->dvert, gps->totpoints};
+    for (const MDeformVert &dvert : dverts) {
+      for (const MDeformWeight &weight : Span<MDeformWeight>{dvert.dw, dvert.totweight}) {
+        is_group_used[weight.def_nr] = true;
+      }
+    }
+  }
+  BLI_listbase_clear(&r_vertex_group_names);
+  r_indices.reinitialize(num_vertex_groups);
+  int new_group_i = 0;
+  int old_group_i;
+  LISTBASE_FOREACH_INDEX (const bDeformGroup *, def_group, &all_names, old_group_i) {
+    if (!is_group_used[old_group_i]) {
+      r_indices[old_group_i] = -1;
+      continue;
+    }
+    r_indices[old_group_i] = new_group_i++;
+
+    bDeformGroup *def_group_copy = static_cast<bDeformGroup *>(MEM_dupallocN(def_group));
+    BLI_addtail(&r_vertex_group_names, def_group_copy);
+  }
+}
+
 void legacy_gpencil_frame_to_grease_pencil_drawing(const bGPDframe &gpf,
+                                                   const ListBase &vertex_group_names,
                                                    GreasePencilDrawing &r_drawing)
 {
   /* Construct an empty CurvesGeometry in-place. */
@@ -54,6 +97,25 @@ void legacy_gpencil_frame_to_grease_pencil_drawing(const bGPDframe &gpf,
   /* All strokes are poly curves. */
   curves.fill_curve_types(CURVE_TYPE_POLY);
 
+  /* Find used vertex groups in this drawing. */
+  ListBase stroke_vertex_group_names;
+  Array<int> stroke_def_nr_map;
+  find_used_vertex_groups(gpf, vertex_group_names, stroke_vertex_group_names, stroke_def_nr_map);
+  BLI_assert(BLI_listbase_is_empty(&curves.vertex_group_names));
+  curves.vertex_group_names = stroke_vertex_group_names;
+  const bool use_dverts = !BLI_listbase_is_empty(&curves.vertex_group_names);
+
+  /* Copy vertex weights and map the vertex group indices. */
+  auto copy_dvert = [&](const MDeformVert &src_dvert, MDeformVert &dst_dvert) {
+    dst_dvert = src_dvert;
+    dst_dvert.dw = static_cast<MDeformWeight *>(MEM_dupallocN(src_dvert.dw));
+    const MutableSpan<MDeformWeight> vertex_weights = {dst_dvert.dw, dst_dvert.totweight};
+    for (MDeformWeight &weight : vertex_weights) {
+      /* Map def_nr to the reduced vertex group list. */
+      weight.def_nr = stroke_def_nr_map[weight.def_nr];
+    }
+  };
+
   /* Point Attributes. */
   MutableSpan<float3> positions = curves.positions_for_write();
   MutableSpan<float> radii = drawing.radii_for_write();
@@ -66,6 +128,8 @@ void legacy_gpencil_frame_to_grease_pencil_drawing(const bGPDframe &gpf,
       attributes.lookup_or_add_for_write_span<ColorGeometry4f>("vertex_color", AttrDomain::Point);
   SpanAttributeWriter<bool> selection = attributes.lookup_or_add_for_write_span<bool>(
       ".selection", AttrDomain::Point);
+  MutableSpan<MDeformVert> dverts = use_dverts ? curves.wrap().deform_verts_for_write() :
+                                                 MutableSpan<MDeformVert>();
 
   /* Curve Attributes. */
   SpanAttributeWriter<bool> stroke_cyclic = attributes.lookup_or_add_for_write_span<bool>(
@@ -126,6 +190,8 @@ void legacy_gpencil_frame_to_grease_pencil_drawing(const bGPDframe &gpf,
     MutableSpan<ColorGeometry4f> stroke_vertex_colors = vertex_colors.span.slice(
         stroke_points_range);
     MutableSpan<bool> stroke_selections = selection.span.slice(stroke_points_range);
+    MutableSpan<MDeformVert> stroke_dverts = use_dverts ? dverts.slice(stroke_points_range) :
+                                                          MutableSpan<MDeformVert>();
 
     /* Do first point. */
     const bGPDspoint &first_pt = stroke_points.first();
@@ -143,6 +209,9 @@ void legacy_gpencil_frame_to_grease_pencil_drawing(const bGPDframe &gpf,
     stroke_rotations.first() = first_pt.uv_rot;
     stroke_vertex_colors.first() = ColorGeometry4f(first_pt.vert_color);
     stroke_selections.first() = (first_pt.flag & GP_SPOINT_SELECT) != 0;
+    if (use_dverts && gps->dvert) {
+      copy_dvert(gps->dvert[0], stroke_dverts.first());
+    }
 
     /* Do the rest of the points. */
     for (const int i : stroke_points.index_range().drop_back(1)) {
@@ -156,6 +225,9 @@ void legacy_gpencil_frame_to_grease_pencil_drawing(const bGPDframe &gpf,
       stroke_rotations[point_i] = pt.uv_rot;
       stroke_vertex_colors[point_i] = ColorGeometry4f(pt.vert_color);
       stroke_selections[point_i] = (pt.flag & GP_SPOINT_SELECT) != 0;
+      if (use_dverts && gps->dvert) {
+        copy_dvert(gps->dvert[point_i], stroke_dverts[point_i]);
+      }
     }
   }
 
@@ -225,7 +297,7 @@ void legacy_gpencil_to_grease_pencil(Main &bmain, GreasePencil &grease_pencil, b
           grease_pencil.drawing_array[i]);
 
       /* Convert the frame to a drawing. */
-      legacy_gpencil_frame_to_grease_pencil_drawing(*gpf, drawing);
+      legacy_gpencil_frame_to_grease_pencil_drawing(*gpf, gpd.vertex_group_names, drawing);
 
       /* Add the frame to the layer. */
       if (GreasePencilFrame *new_frame = new_layer.add_frame(gpf->framenum, i)) {
@@ -242,6 +314,10 @@ void legacy_gpencil_to_grease_pencil(Main &bmain, GreasePencil &grease_pencil, b
     /* TODO: Update drawing user counts. */
   }
 
+  /* Copy vertex group names and settings. */
+  BKE_defgroup_copy_list(&grease_pencil.vertex_group_names, &gpd.vertex_group_names);
+  grease_pencil.vertex_group_active_index = gpd.vertex_group_active_index;
+
   /* Convert the onion skinning settings. */
   grease_pencil.onion_skinning_settings.opacity = gpd.onion_factor;
   grease_pencil.onion_skinning_settings.mode = gpd.onion_mode;