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

@@ -9,6 +9,8 @@
 
 #include "DNA_screen_types.h"
 
+#include "ED_view3d.h"
+
 #include "UI_resources.h"
 
 #include "DRW_engine.h"
@@ -138,29 +140,44 @@ static void select_cache_init(void *vedata)
   DRWState state = DRW_STATE_DEFAULT;
   state |= RV3D_CLIPPING_ENABLED(draw_ctx->v3d, draw_ctx->rv3d) ? DRW_STATE_CLIP_PLANES : 0;
 
+  bool retopology_occlusion = RETOPOLOGY_ENABLED(draw_ctx->v3d) && !XRAY_ENABLED(draw_ctx->v3d);
+  float retopology_offset = RETOPOLOGY_OFFSET(draw_ctx->v3d);
+
   {
     DRW_PASS_CREATE(psl->depth_only_pass, state);
     pd->shgrp_depth_only = DRW_shgroup_create(sh->select_id_uniform, psl->depth_only_pass);
+    /* Not setting ID because this pass only draws to the depth buffer. */
+    DRW_shgroup_uniform_float_copy(pd->shgrp_depth_only, "retopologyOffset", retopology_offset);
+
+    if (retopology_occlusion) {
+      pd->shgrp_occlude = DRW_shgroup_create(sh->select_id_uniform, psl->depth_only_pass);
+      /* Not setting ID because this pass only draws to the depth buffer. */
+      DRW_shgroup_uniform_float_copy(pd->shgrp_occlude, "retopologyOffset", 0.0f);
+    }
 
     DRW_PASS_CREATE(psl->select_id_face_pass, state);
     if (e_data.context.select_mode & SCE_SELECT_FACE) {
       pd->shgrp_face_flat = DRW_shgroup_create(sh->select_id_flat, psl->select_id_face_pass);
+      DRW_shgroup_uniform_float_copy(pd->shgrp_face_flat, "retopologyOffset", retopology_offset);
     }
     else {
       pd->shgrp_face_unif = DRW_shgroup_create(sh->select_id_uniform, psl->select_id_face_pass);
       DRW_shgroup_uniform_int_copy(pd->shgrp_face_unif, "id", 0);
+      DRW_shgroup_uniform_float_copy(pd->shgrp_face_unif, "retopologyOffset", retopology_offset);
     }
 
     if (e_data.context.select_mode & SCE_SELECT_EDGE) {
       DRW_PASS_CREATE(psl->select_id_edge_pass, state | DRW_STATE_FIRST_VERTEX_CONVENTION);
 
       pd->shgrp_edge = DRW_shgroup_create(sh->select_id_flat, psl->select_id_edge_pass);
+      DRW_shgroup_uniform_float_copy(pd->shgrp_edge, "retopologyOffset", retopology_offset);
     }
 
     if (e_data.context.select_mode & SCE_SELECT_VERTEX) {
       DRW_PASS_CREATE(psl->select_id_vert_pass, state);
       pd->shgrp_vert = DRW_shgroup_create(sh->select_id_flat, psl->select_id_vert_pass);
       DRW_shgroup_uniform_float_copy(pd->shgrp_vert, "sizeVertex", 2 * G_draw.block.size_vertex);
+      DRW_shgroup_uniform_float_copy(pd->shgrp_vert, "retopologyOffset", retopology_offset);
     }
   }
 
@@ -197,6 +214,14 @@ static void select_cache_populate(void *vedata, Object *ob)
   SELECTID_StorageList *stl = ((SELECTID_Data *)vedata)->stl;
   const DRWContextState *draw_ctx = DRW_context_state_get();
 
+  if (!DRW_object_is_in_edit_mode(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);
+    }
+    return;
+  }
+
   SELECTID_ObjectData *sel_data = (SELECTID_ObjectData *)DRW_drawdata_get(
       &ob->id, &draw_engine_select_type);
 

source/blender/draw/engines/select/select_private.h

@@ -40,6 +40,7 @@ typedef struct SELECTID_Shaders {
 
 typedef struct SELECTID_PrivateData {
   DRWShadingGroup *shgrp_depth_only;
+  DRWShadingGroup *shgrp_occlude;
   DRWShadingGroup *shgrp_face_unif;
   DRWShadingGroup *shgrp_face_flat;
   DRWShadingGroup *shgrp_edge;

source/blender/draw/engines/select/shaders/infos/select_id_info.hh

@@ -11,6 +11,7 @@ GPU_SHADER_INTERFACE_INFO(select_id_iface, "").flat(Type::INT, "id");
 GPU_SHADER_CREATE_INFO(select_id_flat)
     .push_constant(Type::FLOAT, "sizeVertex")
     .push_constant(Type::INT, "offset")
+    .push_constant(Type::FLOAT, "retopologyOffset")
     .vertex_in(0, Type::VEC3, "pos")
     .vertex_in(1, Type::INT, "index")
     .vertex_out(select_id_iface)
@@ -24,6 +25,7 @@ GPU_SHADER_CREATE_INFO(select_id_uniform)
     .define("UNIFORM_ID")
     .push_constant(Type::FLOAT, "sizeVertex")
     .push_constant(Type::INT, "id")
+    .push_constant(Type::FLOAT, "retopologyOffset")
     .vertex_in(0, Type::VEC3, "pos")
     .fragment_out(0, Type::UINT, "fragColor")
     .vertex_source("select_id_vert.glsl")

source/blender/draw/engines/select/shaders/select_id_vert.glsl

@@ -8,8 +8,12 @@ void main()
 #endif
 
   vec3 world_pos = point_object_to_world(pos);
-  gl_Position = point_world_to_ndc(world_pos);
+  vec3 view_pos = point_world_to_view(world_pos);
+  gl_Position = point_view_to_ndc(view_pos);
   gl_PointSize = sizeVertex;
 
+  /* Offset Z position for retopology selection occlusion. */
+  gl_Position.z += get_homogenous_z_offset(view_pos.z, gl_Position.w, retopologyOffset);
+
   view_clipping_distances(world_pos);
 }

source/blender/draw/intern/draw_manager.c

@@ -2770,6 +2770,25 @@ void DRW_draw_select_id(Depsgraph *depsgraph, ARegion *region, View3D *v3d, cons
       drw_engines_cache_populate(obj_eval);
     }
 
+    if (RETOPOLOGY_ENABLED(v3d) && !XRAY_ENABLED(v3d)) {
+      DEGObjectIterSettings deg_iter_settings = {0};
+      deg_iter_settings.depsgraph = depsgraph;
+      deg_iter_settings.flags = DEG_OBJECT_ITER_FOR_RENDER_ENGINE_FLAGS;
+      DEG_OBJECT_ITER_BEGIN (&deg_iter_settings, ob) {
+        if (ob->type != OB_MESH) {
+          /* The iterator has evaluated meshes for all solid objects.
+           * It also has non-mesh objects however, which are not supported here. */
+          continue;
+        }
+        if (DRW_object_is_in_edit_mode(ob)) {
+          /* Only background (non-edit) objects are used for occlusion. */
+          continue;
+        }
+        drw_engines_cache_populate(ob);
+      }
+      DEG_OBJECT_ITER_END;
+    }
+
     drw_engines_cache_finish();
 
     drw_task_graph_deinit();

source/blender/makesrna/intern/rna_space.c

@@ -4551,7 +4551,10 @@ static void rna_def_space_view3d_overlay(BlenderRNA *brna)
 
   prop = RNA_def_property(srna, "show_retopology", PROP_BOOLEAN, PROP_NONE);
   RNA_def_property_boolean_sdna(prop, NULL, "overlay.edit_flag", V3D_OVERLAY_EDIT_RETOPOLOGY);
-  RNA_def_property_ui_text(prop, "Retopology", "Use retopology display");
+  RNA_def_property_ui_text(prop,
+                           "Retopology",
+                           "Hide the solid mesh and offset the overlay towards the view. "
+                           "Selection is occluded by inactive geometry, unless X-Ray is enabled");
   RNA_def_property_update(prop, NC_SPACE | ND_SPACE_VIEW3D | NS_VIEW3D_SHADING, NULL);
 
   prop = RNA_def_property(srna, "retopology_offset", PROP_FLOAT, PROP_DISTANCE);