Grease Pencil: Add LineArt modifier

This adds the LineArt grease pencil modifier.

It takes objects or collections as input and generates various grease
pencil lines from these objects with the help of the active scene
camera. For example it can generate contour lines, intersection lines
and crease lines to name a few.

This is really useful as artists can then use 3D meshes to automatically
generate grease pencil lines for characters, enviroments or other
visualization purposes.

These lines can then be baked and edited as regular grease pencil lines.

Reviewed By: Sebastian Parborg, Antonio Vazquez, Matias Mendiola

Differential Revision: http://developer.blender.org/D8758

2 files changed, 89 insertions, 1 deletions

diff --git a/source/blender/editors/object/object_add.c b/source/blender/editors/object/object_add.c
index dc941f12eba..e4527740164 100644
--- a/source/blender/editors/object/object_add.c
+++ b/source/blender/editors/object/object_add.c
@@ -31,6 +31,7 @@
 #include "DNA_camera_types.h"
 #include "DNA_collection_types.h"
 #include "DNA_curve_types.h"
+#include "DNA_gpencil_modifier_types.h"
 #include "DNA_gpencil_types.h"
 #include "DNA_key_types.h"
 #include "DNA_light_types.h"
@@ -68,6 +69,7 @@
 #include "BKE_geometry_set.h"
 #include "BKE_gpencil_curve.h"
 #include "BKE_gpencil_geom.h"
+#include "BKE_gpencil_modifier.h"
 #include "BKE_hair.h"
 #include "BKE_key.h"
 #include "BKE_lattice.h"
@@ -1305,7 +1307,7 @@ static bool object_gpencil_add_poll(bContext *C)
 
 static int object_gpencil_add_exec(bContext *C, wmOperator *op)
 {
-  Object *ob = CTX_data_active_object(C);
+  Object *ob = CTX_data_active_object(C), *ob_orig = ob;
   bGPdata *gpd = (ob && (ob->type == OB_GPENCIL)) ? ob->data : NULL;
 
   const int type = RNA_enum_get(op->ptr, "type");
@@ -1333,6 +1335,11 @@ static int object_gpencil_add_exec(bContext *C, wmOperator *op)
         ob_name = "Stroke";
         break;
       }
+      case GP_LRT_OBJECT:
+      case GP_LRT_COLLECTION: {
+        ob_name = "Line Art";
+        break;
+      }
       default: {
         break;
       }
@@ -1373,6 +1380,46 @@ static int object_gpencil_add_exec(bContext *C, wmOperator *op)
       ED_gpencil_create_monkey(C, ob, mat);
       break;
     }
+    case GP_LRT_SCENE:
+    case GP_LRT_COLLECTION:
+    case GP_LRT_OBJECT: {
+      float radius = RNA_float_get(op->ptr, "radius");
+      float mat[4][4];
+
+      ED_object_new_primitive_matrix(C, ob, loc, rot, mat);
+      mul_v3_fl(mat[0], radius);
+      mul_v3_fl(mat[1], radius);
+      mul_v3_fl(mat[2], radius);
+
+      ED_gpencil_create_lineart(C, ob);
+
+      gpd = ob->data;
+
+      /* Add Line Art modifier */
+      LineartGpencilModifierData *md = (LineartGpencilModifierData *)BKE_gpencil_modifier_new(
+          eGpencilModifierType_Lineart);
+      BLI_addtail(&ob->greasepencil_modifiers, md);
+      BKE_gpencil_modifier_unique_name(&ob->greasepencil_modifiers, (GpencilModifierData *)md);
+
+      if (type == GP_LRT_COLLECTION) {
+        md->source_type = LRT_SOURCE_COLLECTION;
+        md->source_collection = CTX_data_collection(C);
+      }
+      else if (type == GP_LRT_OBJECT) {
+        md->source_type = LRT_SOURCE_OBJECT;
+        md->source_object = ob_orig;
+      }
+      else {
+        /* Whole scene. */
+        md->source_type = LRT_SOURCE_SCENE;
+      }
+      /* Only created one layer and one material. */
+      strcpy(md->target_layer, ((bGPDlayer *)gpd->layers.first)->info);
+      md->target_material = BKE_gpencil_material(ob, 1);
+
+      /* Stroke object is drawn in front of meshes by default. */
+      ob->dtx |= OB_DRAW_IN_FRONT;
+    }
     case GP_EMPTY:
       /* do nothing */
       break;
@@ -1393,6 +1440,41 @@ static int object_gpencil_add_exec(bContext *C, wmOperator *op)
   return OPERATOR_FINISHED;
 }
 
+static const EnumPropertyItem *object_gpencil_add_options(bContext *C,
+                                                          PointerRNA *UNUSED(ptr),
+                                                          PropertyRNA *UNUSED(prop),
+                                                          bool *r_free)
+{
+  EnumPropertyItem *item = NULL;
+  const EnumPropertyItem *item_ref = rna_enum_object_gpencil_type_items;
+  int totitem = 0;
+  int i = 0;
+  int orig_count = RNA_enum_items_count(item_ref);
+
+  /* Default types. */
+  for (i = 0; i < orig_count; i++) {
+    if (item_ref[i].value == GP_LRT_OBJECT || item_ref[i].value == GP_LRT_COLLECTION ||
+        item_ref[i].value == GP_LRT_SCENE) {
+      if (item_ref[i].value == GP_LRT_SCENE) {
+        /* separator before line art types */
+        RNA_enum_item_add_separator(&item, &totitem);
+      }
+      else if (item_ref[i].value == GP_LRT_OBJECT) {
+        Object *ob = CTX_data_active_object(C);
+        if (!ob || ob->type != OB_MESH) {
+          continue;
+        }
+      }
+    }
+    RNA_enum_item_add(&item, &totitem, &item_ref[i]);
+  }
+
+  RNA_enum_item_end(&item, &totitem);
+  *r_free = true;
+
+  return item;
+}
+
 void OBJECT_OT_gpencil_add(wmOperatorType *ot)
 {
   /* identifiers */
@@ -1413,6 +1495,7 @@ void OBJECT_OT_gpencil_add(wmOperatorType *ot)
   ED_object_add_generic_props(ot, false);
 
   ot->prop = RNA_def_enum(ot->srna, "type", rna_enum_object_gpencil_type_items, 0, "Type", "");
+  RNA_def_enum_funcs(ot->prop, object_gpencil_add_options);
 }
 
 /** \} */
diff --git a/source/blender/editors/object/object_ops.c b/source/blender/editors/object/object_ops.c
index 57676cf5c76..71bea6bf9e3 100644
--- a/source/blender/editors/object/object_ops.c
+++ b/source/blender/editors/object/object_ops.c
@@ -37,6 +37,8 @@
 
 #include "object_intern.h"
 
+#include "MOD_gpencil_lineart.h"
+
 /* ************************** registration **********************************/
 
 void ED_operatortypes_object(void)
@@ -154,6 +156,9 @@ void ED_operatortypes_object(void)
   WM_operatortype_append(OBJECT_OT_gpencil_modifier_copy);
   WM_operatortype_append(OBJECT_OT_gpencil_modifier_copy_to_selected);
 
+  /* grease pencil line art */
+  WM_operatortypes_lineart();
+
   /* Shader FX. */
   WM_operatortype_append(OBJECT_OT_shaderfx_add);
   WM_operatortype_append(OBJECT_OT_shaderfx_remove);