source/blender/draw/engines/select/select_engine.c

@@ -217,7 +217,7 @@ static void select_cache_populate(void *vedata, Object *ob)
 
   const bool retopology_occlusion = RETOPOLOGY_ENABLED(draw_ctx->v3d) &&
                                     !XRAY_ENABLED(draw_ctx->v3d);
-  if (retopology_occlusion && !DRW_object_is_in_edit_mode(ob)) {
+  if (retopology_occlusion && !DRW_object_should_not_occlude(ob)) {
     if (ob->dt >= OB_SOLID) {
       struct GPUBatch *geom_faces = DRW_mesh_batch_cache_get_surface(ob->data);
       DRW_shgroup_call_obmat(stl->g_data->shgrp_occlude, geom_faces, ob->object_to_world);

source/blender/draw/intern/DRW_render.h

@@ -877,6 +877,14 @@ bool DRW_object_is_renderable(const struct Object *ob);
  * This will not be the case when one of the objects are influenced by modifiers.
  */
 bool DRW_object_is_in_edit_mode(const struct Object *ob);
+
+/**
+ * Should `ob` be used for occlusion in selection when in weight and vertex paint mode, this
+ * is needed for when retopology overlay is enabled to still be able to render IDs for face
+ * and vertex selection.
+ */
+bool DRW_object_should_not_occlude(const Object *ob);
+
 /**
  * Return whether this object is visible depending if
  * we are rendering or drawing in the viewport.

source/blender/draw/intern/draw_manager.c

@@ -210,6 +210,21 @@ bool DRW_object_is_in_edit_mode(const Object *ob)
   return false;
 }
 
+bool DRW_object_should_not_occlude(const Object *ob)
+{
+  if (DRW_object_is_in_edit_mode(ob)) {
+    return true;
+  }
+  if (ob->type == OB_MESH && (ob->mode & OB_MODE_VERTEX_PAINT) ||
+      (ob->mode & OB_MODE_WEIGHT_PAINT)) {
+    Mesh *me = ob->data;
+    if ((ME_EDIT_PAINT_SEL_MODE(me))) {
+      return true;
+    }
+  }
+  return false;
+}
+
 int DRW_object_visibility_in_active_context(const Object *ob)
 {
   const eEvaluationMode mode = DRW_state_is_scene_render() ? DAG_EVAL_RENDER : DAG_EVAL_VIEWPORT;
@@ -2788,7 +2803,7 @@ void DRW_draw_select_id(Depsgraph *depsgraph, ARegion *region, View3D *v3d, cons
            * It also has non-mesh objects however, which are not supported here. */
           continue;
         }
-        if (DRW_object_is_in_edit_mode(ob)) {
+        if (DRW_object_should_not_occlude(ob)) {
           /* Only background (non-edit) objects are used for occlusion. */
           continue;
         }