Eevee: Add per material option to cull backfaces

This is in order to have more flexibility and to have an explicit option
for final renders.

release/scripts/startup/bl_ui/properties_material.py

@@ -212,6 +212,7 @@ class EEVEE_MATERIAL_PT_settings(MaterialButtonsPanel, Panel):
 
         mat = context.material
 
+        layout.prop(mat, "use_backface_culling")
         layout.prop(mat, "blend_method")
         layout.prop(mat, "shadow_method")
 

release/scripts/startup/bl_ui/space_view3d.py

@@ -5082,6 +5082,11 @@ class VIEW3D_PT_shading_options(Panel):
     bl_label = "Options"
     bl_parent_id = 'VIEW3D_PT_shading'
 
+    @classmethod
+    def poll(cls, context):
+        shading = VIEW3D_PT_shading.get_shading(context)
+        return shading.type in {'WIREFRAME', 'SOLID'}
+
     def draw(self, context):
         layout = self.layout
 
@@ -5089,7 +5094,7 @@ class VIEW3D_PT_shading_options(Panel):
 
         col = layout.column()
 
-        if shading.type != 'WIREFRAME':
+        if shading.type == 'SOLID':
             col.prop(shading, "show_backface_culling")
 
         row = col.row(align=True)

source/blender/blenloader/intern/versioning_280.c

@@ -2850,7 +2850,7 @@ void blo_do_versions_280(FileData *fd, Library *UNUSED(lib), Main *bmain)
     }
 
     for (Material *mat = bmain->materials.first; mat; mat = mat->id.next) {
-      mat->blend_flag &= ~(MA_BL_FLAG_UNUSED_2);
+      mat->blend_flag &= ~(1 << 2); /* UNUSED */
     }
   }
 

source/blender/draw/engines/eevee/eevee_materials.c

@@ -1208,7 +1208,6 @@ static void material_opaque(Material *ma,
                             GHash *material_hash,
                             EEVEE_ViewLayerData *sldata,
                             EEVEE_Data *vedata,
-                            bool do_cull,
                             struct GPUMaterial **gpumat,
                             struct GPUMaterial **gpumat_depth,
                             struct DRWShadingGroup **shgrp,
@@ -1228,6 +1227,7 @@ static void material_opaque(Material *ma,
   float *spec_p = &ma->spec;
   float *rough_p = &ma->roughness;
 
+  const bool do_cull = (ma->blend_flag & MA_BL_CULL_BACKFACE) != 0;
   const bool use_gpumat = (ma->use_nodes && ma->nodetree);
   const bool use_ssrefract = ((ma->blend_flag & MA_BL_SS_REFRACTION) != 0) &&
                              ((effects->enabled_effects & EFFECT_REFRACT) != 0);
@@ -1460,7 +1460,6 @@ static void material_opaque(Material *ma,
 static void material_transparent(Material *ma,
                                  EEVEE_ViewLayerData *sldata,
                                  EEVEE_Data *vedata,
-                                 bool do_cull,
                                  struct GPUMaterial **gpumat,
                                  struct DRWShadingGroup **shgrp,
                                  struct DRWShadingGroup **shgrp_depth)
@@ -1471,6 +1470,7 @@ static void material_transparent(Material *ma,
   EEVEE_PassList *psl = ((EEVEE_Data *)vedata)->psl;
   EEVEE_LightsInfo *linfo = sldata->lights;
 
+  const bool do_cull = (ma->blend_flag & MA_BL_CULL_BACKFACE) != 0;
   const bool use_ssrefract = (((ma->blend_flag & MA_BL_SS_REFRACTION) != 0) &&
                               ((stl->effects->enabled_effects & EFFECT_REFRACT) != 0));
   float *color_p = &ma->r;
@@ -1604,8 +1604,6 @@ void EEVEE_materials_cache_populate(EEVEE_Data *vedata,
   Scene *scene = draw_ctx->scene;
   GHash *material_hash = stl->g_data->material_hash;
 
-  const bool do_cull = (draw_ctx->v3d &&
-                        (draw_ctx->v3d->shading.flag & V3D_SHADING_BACKFACE_CULLING));
   bool is_sculpt_mode = DRW_object_use_pbvh_drawing(ob);
   /* For now just force fully shaded with eevee when supported. */
   is_sculpt_mode = is_sculpt_mode &&
@@ -1641,7 +1639,6 @@ void EEVEE_materials_cache_populate(EEVEE_Data *vedata,
                           material_hash,
                           sldata,
                           vedata,
-                          do_cull,
                           &gpumat_array[i],
                           &gpumat_depth_array[i],
                           &shgrp_array[i],
@@ -1654,7 +1651,6 @@ void EEVEE_materials_cache_populate(EEVEE_Data *vedata,
           material_transparent(ma_array[i],
                                sldata,
                                vedata,
-                               do_cull,
                                &gpumat_array[i],
                                &shgrp_array[i],
                                &shgrp_depth_array[i]);

source/blender/makesdna/DNA_material_types.h

@@ -316,7 +316,7 @@ enum {
 enum {
   MA_BL_HIDE_BACKFACE = (1 << 0),
   MA_BL_SS_REFRACTION = (1 << 1),
-  MA_BL_FLAG_UNUSED_2 = (1 << 2), /* cleared */
+  MA_BL_CULL_BACKFACE = (1 << 2),
   MA_BL_TRANSLUCENCY = (1 << 3),
 };
 

source/blender/makesrna/intern/rna_material.c

@@ -791,6 +791,12 @@ void RNA_def_material(BlenderRNA *brna)
                            "(avoids transparency sorting problems)");
   RNA_def_property_update(prop, 0, "rna_Material_draw_update");
 
+  prop = RNA_def_property(srna, "use_backface_culling", PROP_BOOLEAN, PROP_NONE);
+  RNA_def_property_boolean_sdna(prop, NULL, "blend_flag", MA_BL_CULL_BACKFACE);
+  RNA_def_property_ui_text(
+      prop, "Backface Culling", "Use back face culling to hide the back side of faces");
+  RNA_def_property_update(prop, 0, "rna_Material_draw_update");
+
   prop = RNA_def_property(srna, "use_screen_refraction", PROP_BOOLEAN, PROP_NONE);
   RNA_def_property_boolean_sdna(prop, NULL, "blend_flag", MA_BL_SS_REFRACTION);
   RNA_def_property_ui_text(