intern/cycles/blender/addon/ui.py

@@ -2271,6 +2271,7 @@ class CYCLES_RENDER_PT_simplify_viewport(CyclesButtonsPanel, Panel):
         col.prop(rd, "simplify_child_particles", text="Child Particles")
         col.prop(cscene, "texture_limit", text="Texture Limit")
         col.prop(rd, "simplify_volumes", text="Volume Resolution")
+        col.prop(rd, "use_simplify_normals", text="Normals")
 
 
 class CYCLES_RENDER_PT_simplify_render(CyclesButtonsPanel, Panel):

scripts/startup/bl_ui/properties_render.py

@@ -1197,6 +1197,9 @@ class RENDER_PT_simplify_viewport(RenderButtonsPanel, Panel):
             col = flow.column()
             col.prop(rd, "simplify_shadows", text="Shadow Resolution")
 
+        col = flow.column()
+        col.prop(rd, "use_simplify_normals", text="Normals")
+
 
 class RENDER_PT_simplify_render(RenderButtonsPanel, Panel):
     bl_label = "Render"

source/blender/blenloader/intern/versioning_280.cc

@@ -4652,7 +4652,7 @@ void blo_do_versions_280(FileData *fd, Library * /*lib*/, Main *bmain)
                          R_MODE_UNUSED_5 | R_MODE_UNUSED_6 | R_MODE_UNUSED_7 | R_MODE_UNUSED_8 |
                          R_MODE_UNUSED_10 | R_MODE_UNUSED_13 | R_MODE_UNUSED_16 |
                          R_MODE_UNUSED_17 | R_MODE_UNUSED_18 | R_MODE_UNUSED_19 |
-                         R_MODE_UNUSED_20 | R_MODE_UNUSED_21 | R_MODE_UNUSED_27);
+                         R_MODE_UNUSED_20 | R_MODE_UNUSED_21 | R_SIMPLIFY_NORMALS);
 
       scene->r.scemode &= ~(R_SCEMODE_UNUSED_8 | R_SCEMODE_UNUSED_11 | R_SCEMODE_UNUSED_13 |
                             R_SCEMODE_UNUSED_16 | R_SCEMODE_UNUSED_17 | R_SCEMODE_UNUSED_19);

source/blender/draw/intern/draw_cache_extract_mesh.cc

@@ -686,6 +686,7 @@ void mesh_buffer_cache_create_requested(TaskGraph *task_graph,
   mr->use_hide = use_hide;
   mr->use_subsurf_fdots = mr->me && !mr->me->runtime->subsurf_face_dot_tags.is_empty();
   mr->use_final_mesh = do_final;
+  mr->use_simplify_normals = (scene->r.mode & R_SIMPLIFY) && (scene->r.mode & R_SIMPLIFY_NORMALS);
 
 #ifdef DEBUG_TIME
   double rdata_end = PIL_check_seconds_timer();

source/blender/draw/intern/draw_cache_extract_mesh_render_data.cc

@@ -413,9 +413,10 @@ void mesh_render_data_update_normals(MeshRenderData &mr, const eMRDataType data_
     if (data_flag & (MR_DATA_POLY_NOR | MR_DATA_LOOP_NOR | MR_DATA_TAN_LOOP_NOR)) {
       mr.face_normals = mr.me->face_normals();
     }
-    if (((data_flag & MR_DATA_LOOP_NOR) && ELEM(mr.me->normals_domain(),
+    if (((data_flag & MR_DATA_LOOP_NOR) && !mr.use_simplify_normals &&
-                                                blender::bke::MeshNormalDomain::Corner,
+         ELEM(mr.me->normals_domain(),
-                                                blender::bke::MeshNormalDomain::Face)) ||
+              blender::bke::MeshNormalDomain::Corner,
+              blender::bke::MeshNormalDomain::Face)) ||
         (data_flag & MR_DATA_TAN_LOOP_NOR))
     {
       mr.loop_normals = mr.me->corner_normals();

source/blender/draw/intern/mesh_extractors/extract_mesh.hh

@@ -51,6 +51,7 @@ struct MeshRenderData {
   bool use_subsurf_fdots;
   bool use_final_mesh;
   bool hide_unmapped_edges;
+  bool use_simplify_normals;
 
   /** Use for #MeshStatVis calculation which use world-space coords. */
   float obmat[4][4];

source/blender/makesdna/DNA_scene_types.h

@@ -2114,9 +2114,9 @@ enum {
   R_NO_OVERWRITE = 1 << 22,   /* Skip existing files. */
   R_TOUCH = 1 << 23,          /* Touch files before rendering. */
   R_SIMPLIFY = 1 << 24,
-  R_EDGE_FRS = 1 << 25,        /* R_EDGE reserved for Freestyle */
+  R_EDGE_FRS = 1 << 25,         /* R_EDGE reserved for Freestyle */
-  R_PERSISTENT_DATA = 1 << 26, /* Keep data around for re-render. */
+  R_PERSISTENT_DATA = 1 << 26,  /* Keep data around for re-render. */
-  R_MODE_UNUSED_27 = 1 << 27,  /* cleared */
+  R_SIMPLIFY_NORMALS = 1 << 27, /* cleared */
 };
 
 /** #RenderData::seq_flag */

source/blender/makesrna/intern/rna_scene.cc

@@ -7049,6 +7049,16 @@ static void rna_def_scene_render_data(BlenderRNA *brna)
       prop, "Simplify Volumes", "Resolution percentage of volume objects in viewport");
   RNA_def_property_update(prop, 0, "rna_Scene_simplify_update");
 
+  prop = RNA_def_property(srna, "use_simplify_normals", PROP_BOOLEAN, PROP_NONE);
+  RNA_def_property_boolean_sdna(prop, nullptr, "mode", R_SIMPLIFY_NORMALS);
+  RNA_def_property_ui_text(
+      prop,
+      "Mesh Normals",
+      "Skip computing custom normals and face corner normals for the viewport");
+  /* Note: Unlike other simplify properties, this doesn't recalculate objects, since it just
+   * affects viewport drawing. */
+  RNA_def_property_update(prop, NC_SCENE | ND_RENDER_OPTIONS, nullptr);
+
   /* EEVEE - Simplify Options */
   prop = RNA_def_property(srna, "simplify_shadows_render", PROP_FLOAT, PROP_FACTOR);
   RNA_def_property_float_default(prop, 1.0);