Geometry Nodes: viewport preview

This adds support for showing geometry passed to the Viewer in the 3d
viewport (instead of just in the spreadsheet). The "viewer geometry"
bypasses the group output. So it is not necessary to change the final
output of the node group to be able to see the intermediate geometry.

**Activation and deactivation of a viewer node**
* A viewer node is activated by clicking on it.
* Ctrl+shift+click on any node/socket connects it to the viewer and
  makes it active.
* Ctrl+shift+click in empty space deactivates the active viewer.
* When the active viewer is not visible anymore (e.g. another object
  is selected, or the current node group is exit), it is deactivated.
* Clicking on the icon in the header of the Viewer node toggles whether
  its active or not.

**Pinning**
* The spreadsheet still allows pinning the active viewer as before.
  When pinned, the spreadsheet still references the viewer node even
  when it becomes inactive.
* The viewport does not support pinning at the moment. It always shows
  the active viewer.

**Attribute**
* When a field is linked to the second input of the viewer node it is
  displayed as an overlay in the viewport.
* When possible the correct domain for the attribute is determined
  automatically. This does not work in all cases. It falls back to the
  face corner domain on meshes and the point domain on curves. When
  necessary, the domain can be picked manually.
* The spreadsheet now only shows the "Viewer" column for the domain
  that is selected in the Viewer node.
* Instance attributes are visualized as a constant color per instance.

**Viewport Options**
* The attribute overlay opacity can be controlled with the "Viewer Node"
  setting in the overlays popover.
* A viewport can be configured not to show intermediate viewer-geometry
  by disabling the "Viewer Node" option in the "View" menu.

**Implementation Details**
* The "spreadsheet context path" was generalized to a "viewer path" that
  is used in more places now.
* The viewer node itself determines the attribute domain, evaluates the
  field and stores the result in a `.viewer` attribute.
* A new "viewer attribute' overlay displays the data from the `.viewer`
  attribute.
* The ground truth for the active viewer node is stored in the workspace
  now. Node editors, spreadsheets and viewports retrieve the active
  viewer from there unless they are pinned.
* The depsgraph object iterator has a new "viewer path" setting. When set,
  the viewed geometry of the corresponding object is part of the iterator
  instead of the final evaluated geometry.
* To support the instance attribute overlay `DupliObject` was extended
  to contain the information necessary for drawing the overlay.
* The ctrl+shift+click operator has been refactored so that it can make
  existing links to viewers active again.
* The auto-domain-detection in the Viewer node works by checking the
  "preferred domain" for every field input. If there is not exactly one
  preferred domain, the fallback is used.

Known limitations:
* Loose edges of meshes don't have the attribute overlay. This could be
  added separately if necessary.
* Some attributes are hard to visualize as a color directly. For example,
  the values might have to be normalized or some should be drawn as arrays.
  For now, we encourage users to build node groups that generate appropriate
  viewer-geometry. We might include some of that functionality in future versions.
  Support for displaying attribute values as text in the viewport is planned as well.
* There seems to be an issue with the attribute overlay for pointclouds on
  nvidia gpus, to be investigated.

Differential Revision: https://developer.blender.org/D15954

2 files changed, 69 insertions, 102 deletions

diff --git a/source/blender/makesrna/intern/rna_nodetree.c b/source/blender/makesrna/intern/rna_nodetree.c
index c9f63e7c315..4ec2799186e 100644
--- a/source/blender/makesrna/intern/rna_nodetree.c
+++ b/source/blender/makesrna/intern/rna_nodetree.c
@@ -10803,6 +10803,12 @@ static void def_geo_viewer(StructRNA *srna)
   RNA_def_property_enum_default(prop, CD_PROP_FLOAT);
   RNA_def_property_ui_text(prop, "Data Type", "");
   RNA_def_property_update(prop, NC_NODE | NA_EDITED, "rna_GeometryNode_socket_update");
+
+  prop = RNA_def_property(srna, "domain", PROP_ENUM, PROP_NONE);
+  RNA_def_property_enum_items(prop, rna_enum_attribute_domain_with_auto_items);
+  RNA_def_property_enum_default(prop, ATTR_DOMAIN_POINT);
+  RNA_def_property_ui_text(prop, "Domain", "Domain to evaluate the field on");
+  RNA_def_property_update(prop, NC_NODE | NA_EDITED, "rna_Node_update");
 }
 
 static void def_geo_realize_instances(StructRNA *srna)
diff --git a/source/blender/makesrna/intern/rna_space.c b/source/blender/makesrna/intern/rna_space.c
index 9bbe37b5187..738b41828e0 100644
--- a/source/blender/makesrna/intern/rna_space.c
+++ b/source/blender/makesrna/intern/rna_space.c
@@ -19,6 +19,7 @@
 #include "BKE_movieclip.h"
 #include "BKE_node.h"
 #include "BKE_studiolight.h"
+#include "BKE_viewer_path.h"
 
 #include "ED_asset.h"
 #include "ED_spreadsheet.h"
@@ -3279,59 +3280,21 @@ const EnumPropertyItem *rna_SpaceSpreadsheet_attribute_domain_itemf(bContext *UN
   return item_array;
 }
 
-static SpreadsheetContext *rna_SpaceSpreadsheet_context_path_append(SpaceSpreadsheet *sspreadsheet,
-                                                                    int type)
+static StructRNA *rna_viewer_path_elem_refine(PointerRNA *ptr)
 {
-  SpreadsheetContext *context = ED_spreadsheet_context_new(type);
-  BLI_addtail(&sspreadsheet->context_path, context);
-  ED_spreadsheet_context_path_update_tag(sspreadsheet);
-  WM_main_add_notifier(NC_SPACE | ND_SPACE_SPREADSHEET, NULL);
-  return context;
-}
-
-static void rna_SpaceSpreadsheet_context_path_clear(SpaceSpreadsheet *sspreadsheet)
-{
-  ED_spreadsheet_context_path_clear(sspreadsheet);
-  ED_spreadsheet_context_path_update_tag(sspreadsheet);
-  WM_main_add_notifier(NC_SPACE | ND_SPACE_SPREADSHEET, NULL);
-}
-
-static StructRNA *rna_spreadsheet_context_refine(PointerRNA *ptr)
-{
-  SpreadsheetContext *context = ptr->data;
-  switch (context->type) {
-    case SPREADSHEET_CONTEXT_OBJECT:
-      return &RNA_SpreadsheetContextObject;
-    case SPREADSHEET_CONTEXT_MODIFIER:
-      return &RNA_SpreadsheetContextModifier;
-    case SPREADSHEET_CONTEXT_NODE:
-      return &RNA_SpreadsheetContextNode;
+  ViewerPathElem *elem = ptr->data;
+  switch (elem->type) {
+    case VIEWER_PATH_ELEM_TYPE_ID:
+      return &RNA_IDViewerPathElem;
+    case VIEWER_PATH_ELEM_TYPE_MODIFIER:
+      return &RNA_ModifierViewerPathElem;
+    case VIEWER_PATH_ELEM_TYPE_NODE:
+      return &RNA_NodeViewerPathElem;
   }
   BLI_assert_unreachable();
   return NULL;
 }
 
-static void rna_spreadsheet_context_update(Main *UNUSED(bmain),
-                                           Scene *UNUSED(scene),
-                                           PointerRNA *ptr)
-{
-  bScreen *screen = (bScreen *)ptr->owner_id;
-  LISTBASE_FOREACH (ScrArea *, area, &screen->areabase) {
-    SpaceLink *sl = area->spacedata.first;
-    if (sl->spacetype == SPACE_SPREADSHEET) {
-      SpaceSpreadsheet *sspreadsheet = (SpaceSpreadsheet *)sl;
-      ED_spreadsheet_context_path_update_tag(sspreadsheet);
-    }
-  }
-}
-
-static void rna_SpaceSpreadsheet_context_path_guess(SpaceSpreadsheet *sspreadsheet, bContext *C)
-{
-  ED_spreadsheet_context_path_guess(C, sspreadsheet);
-  ED_spreadsheet_context_path_update_tag(sspreadsheet);
-  WM_main_add_notifier(NC_SPACE | ND_SPACE_SPREADSHEET, NULL);
-}
-
 static void rna_FileAssetSelectParams_catalog_id_get(PointerRNA *ptr, char *value)
 {
   const FileAssetSelectParams *params = ptr->data;
@@ -4456,6 +4419,20 @@ static void rna_def_space_view3d_overlay(BlenderRNA *brna)
   RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);
   RNA_def_property_update(prop, NC_SPACE | ND_SPACE_VIEW3D, NULL);
 
+  prop = RNA_def_property(srna, "show_viewer_attribute", PROP_BOOLEAN, PROP_NONE);
+  RNA_def_property_boolean_sdna(prop, NULL, "overlay.flag", V3D_OVERLAY_VIEWER_ATTRIBUTE);
+  RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);
+  RNA_def_property_ui_text(prop, "Viewer Node", "Show attribute overlay for active viewer node");
+  RNA_def_property_update(prop, NC_SPACE | ND_SPACE_VIEW3D, NULL);
+
+  prop = RNA_def_property(srna, "viewer_attribute_opacity", PROP_FLOAT, PROP_FACTOR);
+  RNA_def_property_float_sdna(prop, NULL, "overlay.viewer_attribute_opacity");
+  RNA_def_property_ui_text(
+      prop, "Viewer Attribute Opacity", "Opacity of the attribute that is currently visualized");
+  RNA_def_property_range(prop, 0.0f, 1.0f);
+  RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);
+  RNA_def_property_update(prop, NC_SPACE | ND_SPACE_VIEW3D, NULL);
+
   prop = RNA_def_property(srna, "show_paint_wire", PROP_BOOLEAN, PROP_NONE);
   RNA_def_property_boolean_sdna(prop, NULL, "overlay.paint_flag", V3D_OVERLAY_PAINT_WIRE);
   RNA_def_property_ui_text(prop, "Show Wire", "Use wireframe display in painting modes");
@@ -5107,6 +5084,11 @@ static void rna_def_space_view3d(BlenderRNA *brna)
   RNA_def_property_clear_flag(prop, PROP_EDITABLE);
   RNA_def_property_ui_text(prop, "Visibility Icon", "");
 
+  prop = RNA_def_property(srna, "show_viewer", PROP_BOOLEAN, PROP_NONE);
+  RNA_def_property_boolean_sdna(prop, NULL, "flag2", V3D_SHOW_VIEWER);
+  RNA_def_property_ui_text(prop, "Show Viewer", "Display non-final geometry from viewer nodes");
+  RNA_def_property_update(prop, NC_SPACE | ND_SPACE_VIEW3D | NS_VIEW3D_SHADING, NULL);
+
   /* Nested Structs */
   prop = RNA_def_property(srna, "shading", PROP_POINTER, PROP_NONE);
   RNA_def_property_flag(prop, PROP_NEVER_NULL);
@@ -7883,93 +7865,77 @@ static void rna_def_spreadsheet_row_filter(BlenderRNA *brna)
   RNA_def_property_update(prop, NC_SPACE | ND_SPACE_SPREADSHEET, NULL);
 }
 
-static const EnumPropertyItem spreadsheet_context_type_items[] = {
-    {SPREADSHEET_CONTEXT_OBJECT, "OBJECT", ICON_NONE, "Object", ""},
-    {SPREADSHEET_CONTEXT_MODIFIER, "MODIFIER", ICON_NONE, "Modifier", ""},
-    {SPREADSHEET_CONTEXT_NODE, "NODE", ICON_NONE, "Node", ""},
+static const EnumPropertyItem viewer_path_elem_type_items[] = {
+    {VIEWER_PATH_ELEM_TYPE_ID, "ID", ICON_NONE, "ID", ""},
+    {VIEWER_PATH_ELEM_TYPE_MODIFIER, "MODIFIER", ICON_NONE, "Modifier", ""},
+    {VIEWER_PATH_ELEM_TYPE_NODE, "NODE", ICON_NONE, "Node", ""},
     {0, NULL, 0, NULL, NULL},
 };
 
-static void rna_def_space_spreadsheet_context(BlenderRNA *brna)
+static void rna_def_viewer_path_elem(BlenderRNA *brna)
 {
   StructRNA *srna;
   PropertyRNA *prop;
 
-  srna = RNA_def_struct(brna, "SpreadsheetContext", NULL);
-  RNA_def_struct_ui_text(srna, "Spreadsheet Context", "Element of spreadsheet context path");
-  RNA_def_struct_refine_func(srna, "rna_spreadsheet_context_refine");
+  srna = RNA_def_struct(brna, "ViewerPathElem", NULL);
+  RNA_def_struct_ui_text(srna, "Viewer Path Element", "Element of a viewer path");
+  RNA_def_struct_refine_func(srna, "rna_viewer_path_elem_refine");
 
   prop = RNA_def_property(srna, "type", PROP_ENUM, PROP_NONE);
-  RNA_def_property_enum_items(prop, spreadsheet_context_type_items);
-  RNA_def_property_ui_text(prop, "Type", "Type of the context");
+  RNA_def_property_enum_items(prop, viewer_path_elem_type_items);
+  RNA_def_property_ui_text(prop, "Type", "Type of the path element");
   RNA_def_property_clear_flag(prop, PROP_EDITABLE);
-
-  rna_def_space_generic_show_region_toggles(srna,
-                                            (1 << RGN_TYPE_CHANNELS) | (1 << RGN_TYPE_FOOTER));
 }
 
-static void rna_def_space_spreadsheet_context_object(BlenderRNA *brna)
+static void rna_def_id_viewer_path_elem(BlenderRNA *brna)
 {
   StructRNA *srna;
   PropertyRNA *prop;
 
-  srna = RNA_def_struct(brna, "SpreadsheetContextObject", "SpreadsheetContext");
+  srna = RNA_def_struct(brna, "IDViewerPathElem", "ViewerPathElem");
 
-  prop = RNA_def_property(srna, "object", PROP_POINTER, PROP_NONE);
-  RNA_def_property_struct_type(prop, "Object");
-  RNA_def_property_flag(prop, PROP_EDITABLE);
-  RNA_def_property_update(prop, NC_SPACE | ND_SPACE_SPREADSHEET, "rna_spreadsheet_context_update");
+  prop = RNA_def_property(srna, "id", PROP_POINTER, PROP_NONE);
+  RNA_def_property_ui_text(prop, "ID", "");
 }
 
-static void rna_def_space_spreadsheet_context_modifier(BlenderRNA *brna)
+static void rna_def_modifier_viewer_path_elem(BlenderRNA *brna)
 {
   StructRNA *srna;
   PropertyRNA *prop;
 
-  srna = RNA_def_struct(brna, "SpreadsheetContextModifier", "SpreadsheetContext");
+  srna = RNA_def_struct(brna, "ModifierViewerPathElem", "ViewerPathElem");
 
   prop = RNA_def_property(srna, "modifier_name", PROP_STRING, PROP_NONE);
   RNA_def_property_ui_text(prop, "Modifier Name", "");
-  RNA_def_property_update(prop, NC_SPACE | ND_SPACE_SPREADSHEET, "rna_spreadsheet_context_update");
 }
 
-static void rna_def_space_spreadsheet_context_node(BlenderRNA *brna)
+static void rna_def_node_viewer_path_elem(BlenderRNA *brna)
 {
   StructRNA *srna;
   PropertyRNA *prop;
 
-  srna = RNA_def_struct(brna, "SpreadsheetContextNode", "SpreadsheetContext");
+  srna = RNA_def_struct(brna, "NodeViewerPathElem", "ViewerPathElem");
 
   prop = RNA_def_property(srna, "node_name", PROP_STRING, PROP_NONE);
   RNA_def_property_ui_text(prop, "Node Name", "");
-  RNA_def_property_update(prop, NC_SPACE | ND_SPACE_SPREADSHEET, "rna_spreadsheet_context_update");
 }
 
-static void rna_def_space_spreadsheet_context_path(BlenderRNA *brna, PropertyRNA *cprop)
+static void rna_def_viewer_path(BlenderRNA *brna)
 {
   StructRNA *srna;
-  PropertyRNA *parm;
-  FunctionRNA *func;
-
-  RNA_def_property_srna(cprop, "SpreadsheetContextPath");
-  srna = RNA_def_struct(brna, "SpreadsheetContextPath", NULL);
-  RNA_def_struct_sdna(srna, "SpaceSpreadsheet");
+  PropertyRNA *prop;
 
-  func = RNA_def_function(srna, "append", "rna_SpaceSpreadsheet_context_path_append");
-  RNA_def_function_ui_description(func, "Append a context path element");
-  parm = RNA_def_property(func, "type", PROP_ENUM, PROP_NONE);
-  RNA_def_parameter_flags(parm, 0, PARM_REQUIRED);
-  RNA_def_property_enum_items(parm, spreadsheet_context_type_items);
-  parm = RNA_def_pointer(
-      func, "context", "SpreadsheetContext", "", "Newly created context path element");
-  RNA_def_function_return(func, parm);
+  rna_def_viewer_path_elem(brna);
+  rna_def_id_viewer_path_elem(brna);
+  rna_def_modifier_viewer_path_elem(brna);
+  rna_def_node_viewer_path_elem(brna);
 
-  func = RNA_def_function(srna, "clear", "rna_SpaceSpreadsheet_context_path_clear");
-  RNA_def_function_ui_description(func, "Clear entire context path");
+  srna = RNA_def_struct(brna, "ViewerPath", NULL);
+  RNA_def_struct_ui_text(srna, "Viewer Path", "Path to data that is viewed");
 
-  func = RNA_def_function(srna, "guess", "rna_SpaceSpreadsheet_context_path_guess");
-  RNA_def_function_ui_description(func, "Guess the context path from the current context");
-  RNA_def_function_flag(func, FUNC_USE_CONTEXT);
+  prop = RNA_def_property(srna, "path", PROP_COLLECTION, PROP_NONE);
+  RNA_def_property_struct_type(prop, "ViewerPathElem");
+  RNA_def_property_ui_text(prop, "Viewer Path", NULL);
 }
 
 static void rna_def_space_spreadsheet(BlenderRNA *brna)
@@ -7996,11 +7962,6 @@ static void rna_def_space_spreadsheet(BlenderRNA *brna)
       {0, NULL, 0, NULL, NULL},
   };
 
-  rna_def_space_spreadsheet_context(brna);
-  rna_def_space_spreadsheet_context_object(brna);
-  rna_def_space_spreadsheet_context_modifier(brna);
-  rna_def_space_spreadsheet_context_node(brna);
-
   srna = RNA_def_struct(brna, "SpaceSpreadsheet", "Space");
   RNA_def_struct_ui_text(srna, "Space Spreadsheet", "Spreadsheet space data");
 
@@ -8017,15 +7978,14 @@ static void rna_def_space_spreadsheet(BlenderRNA *brna)
   RNA_def_property_ui_text(prop, "Use Filter", "");
   RNA_def_property_update(prop, NC_SPACE | ND_SPACE_SPREADSHEET, NULL);
 
-  prop = RNA_def_property(srna, "display_context_path_collapsed", PROP_BOOLEAN, PROP_NONE);
+  prop = RNA_def_property(srna, "display_viewer_path_collapsed", PROP_BOOLEAN, PROP_NONE);
   RNA_def_property_boolean_sdna(prop, NULL, "flag", SPREADSHEET_FLAG_CONTEXT_PATH_COLLAPSED);
   RNA_def_property_ui_text(prop, "Display Context Path Collapsed", "");
   RNA_def_property_update(prop, NC_SPACE | ND_SPACE_SPREADSHEET, NULL);
 
-  prop = RNA_def_property(srna, "context_path", PROP_COLLECTION, PROP_NONE);
-  RNA_def_property_struct_type(prop, "SpreadsheetContext");
-  RNA_def_property_ui_text(prop, "Context Path", "Context path to the data being displayed");
-  rna_def_space_spreadsheet_context_path(brna, prop);
+  prop = RNA_def_property(srna, "viewer_path", PROP_POINTER, PROP_NONE);
+  RNA_def_property_ui_text(
+      prop, "Viewer Path", "Path to the data that is displayed in the spreadsheet");
 
   prop = RNA_def_property(srna, "show_only_selected", PROP_BOOLEAN, PROP_NONE);
   RNA_def_property_boolean_sdna(prop, NULL, "filter_flag", SPREADSHEET_FILTER_SELECTED_ONLY);
@@ -8073,6 +8033,7 @@ static void rna_def_space_spreadsheet(BlenderRNA *brna)
 void RNA_def_space(BlenderRNA *brna)
 {
   rna_def_space(brna);
+  rna_def_viewer_path(brna);
   rna_def_space_image(brna);
   rna_def_space_sequencer(brna);
   rna_def_space_text(brna);