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

11 files changed, 222 insertions, 1 deletions

diff --git a/source/blender/makesdna/DNA_collection_types.h b/source/blender/makesdna/DNA_collection_types.h
index 0a80e00d456..f5fcb0b190e 100644
--- a/source/blender/makesdna/DNA_collection_types.h
+++ b/source/blender/makesdna/DNA_collection_types.h
@@ -46,6 +46,14 @@ typedef struct CollectionChild {
   struct Collection *collection;
 } CollectionChild;
 
+enum CollectionFeatureLine_Usage {
+  COLLECTION_LRT_INCLUDE = 0,
+  COLLECTION_LRT_OCCLUSION_ONLY = (1 << 0),
+  COLLECTION_LRT_EXCLUDE = (1 << 1),
+  COLLECTION_LRT_INTERSECTION_ONLY = (1 << 2),
+  COLLECTION_LRT_NO_INTERSECTION = (1 << 3),
+};
+
 typedef struct Collection {
   ID id;
 
@@ -63,8 +71,10 @@ typedef struct Collection {
   /* Runtime-only, always cleared on file load. */
   short tag;
 
+  /** Line Art engine specific */
+  short lineart_usage;
+
   int16_t color_tag;
-  char _pad[2];
 
   /* Runtime. Cache of objects in this collection and all its
    * children. This is created on demand when e.g. some physics
@@ -72,6 +82,9 @@ typedef struct Collection {
    * collections due to memory usage reasons. */
   ListBase object_cache;
 
+  /* Need this for line art sub-collection selections. */
+  ListBase object_cache_instanced;
+
   /* Runtime. List of collections that are a parent of this
    * datablock. */
   ListBase parents;
@@ -89,6 +102,7 @@ enum {
   COLLECTION_RESTRICT_RENDER = (1 << 3),           /* Disable in renders. */
   COLLECTION_HAS_OBJECT_CACHE = (1 << 4),          /* Runtime: object_cache is populated. */
   COLLECTION_IS_MASTER = (1 << 5), /* Is master collection embedded in the scene. */
+  COLLECTION_HAS_OBJECT_CACHE_INSTANCED = (1 << 6), /* for object_cache_instanced. */
 };
 
 /* Collection->tag */
diff --git a/source/blender/makesdna/DNA_gpencil_modifier_defaults.h b/source/blender/makesdna/DNA_gpencil_modifier_defaults.h
index 11d4ee1b2cd..baf2b2414fa 100644
--- a/source/blender/makesdna/DNA_gpencil_modifier_defaults.h
+++ b/source/blender/makesdna/DNA_gpencil_modifier_defaults.h
@@ -283,4 +283,17 @@
     .colorband = NULL, \
   }
 
+#define _DNA_DEFAULT_LineartGpencilModifierData \
+  { \
+    .line_types = LRT_EDGE_FLAG_ALL_TYPE, \
+    .thickness = 25, \
+    .opacity = 1.0f, \
+    .flags = LRT_GPENCIL_MATCH_OUTPUT_VGROUP | LRT_GPENCIL_SOFT_SELECTION, \
+    .crease_threshold = DEG2RAD(140.0f), \
+    .calculation_flags = LRT_ALLOW_DUPLI_OBJECTS | LRT_REMOVE_DOUBLES | LRT_ALLOW_OVERLAPPING_EDGES | LRT_ALLOW_CLIPPING_BOUNDARIES, \
+    .angle_splitting_threshold = DEG2RAD(60.0f), \
+    .chaining_geometry_threshold = 0.001f, \
+    .chaining_image_threshold = 0.001f, \
+  }
+
 /* clang-format off */
diff --git a/source/blender/makesdna/DNA_gpencil_modifier_types.h b/source/blender/makesdna/DNA_gpencil_modifier_types.h
index b2d62e0a5f6..a9262bf7ca4 100644
--- a/source/blender/makesdna/DNA_gpencil_modifier_types.h
+++ b/source/blender/makesdna/DNA_gpencil_modifier_types.h
@@ -53,6 +53,7 @@ typedef enum GpencilModifierType {
   eGpencilModifierType_Time = 16,
   eGpencilModifierType_Multiply = 17,
   eGpencilModifierType_Texture = 18,
+  eGpencilModifierType_Lineart = 19,
   /* Keep last. */
   NUM_GREASEPENCIL_MODIFIER_TYPES,
 } GpencilModifierType;
@@ -809,6 +810,78 @@ typedef enum eTextureGpencil_Mode {
   STROKE_AND_FILL = 2,
 } eTextureGpencil_Mode;
 
+typedef enum eLineartGpencilModifierSource {
+  LRT_SOURCE_COLLECTION = 0,
+  LRT_SOURCE_OBJECT = 1,
+  LRT_SOURCE_SCENE = 2,
+} eLineartGpencilModifierSource;
+
+typedef enum eLineArtGPencilModifierFlags {
+  LRT_GPENCIL_INVERT_SOURCE_VGROUP = (1 << 0),
+  LRT_GPENCIL_MATCH_OUTPUT_VGROUP = (1 << 1),
+  LRT_GPENCIL_SOFT_SELECTION = (1 << 2),
+  LRT_GPENCIL_IS_BAKED = (1 << 3),
+} eLineArtGPencilModifierFlags;
+
+typedef enum eLineartGpencilTransparencyFlags {
+  LRT_GPENCIL_TRANSPARENCY_ENABLE = (1 << 0),
+  /** Set to true means using "and" instead of "or" logic on mask bits. */
+  LRT_GPENCIL_TRANSPARENCY_MATCH = (1 << 1),
+} eLineartGpencilTransparencyFlags;
+
+typedef struct LineartGpencilModifierData {
+  GpencilModifierData modifier;
+
+  short line_types; /* line type enable flags, bits in eLineartEdgeFlag */
+
+  char source_type; /* Object or Collection, from eLineartGpencilModifierSource */
+
+  char use_multiple_levels;
+  short level_start;
+  short level_end;
+
+  struct Object *source_object;
+  struct Collection *source_collection;
+
+  struct Material *target_material;
+  char target_layer[64];
+
+  /** These two variables are to pass on vertex group information from mesh to strokes.
+   * vgname specifies which vertex groups our strokes from source_vertex_group will go to. */
+  char source_vertex_group[64];
+  char vgname[64];
+
+  float opacity;
+  short thickness;
+
+  unsigned char transparency_flags; /* eLineartGpencilTransparencyFlags */
+  unsigned char transparency_mask;
+
+  /** 0-1 range for cosine angle */
+  float crease_threshold;
+
+  /**  0-PI angle, for splitting strokes at sharp points */
+  float angle_splitting_threshold;
+
+  /* CPU mode */
+  float chaining_geometry_threshold;
+  float chaining_image_threshold;
+
+  float pre_sample_length;
+
+  /* Ported from SceneLineArt flags. */
+  int calculation_flags;
+
+  /* Additional Switches. */
+  int flags;
+
+  int _pad;
+
+  /* Runtime only. */
+  void *render_buffer;
+
+} LineartGpencilModifierData;
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/source/blender/makesdna/DNA_gpencil_types.h b/source/blender/makesdna/DNA_gpencil_types.h
index 9d969a29add..8facdca2f9c 100644
--- a/source/blender/makesdna/DNA_gpencil_types.h
+++ b/source/blender/makesdna/DNA_gpencil_types.h
@@ -34,6 +34,7 @@ extern "C" {
 struct AnimData;
 struct Curve;
 struct MDeformVert;
+struct Curve;
 
 #define GP_DEFAULT_PIX_FACTOR 1.0f
 #define GP_DEFAULT_GRID_LINES 4
@@ -412,6 +413,8 @@ typedef enum eGPDframe_Flag {
   GP_FRAME_PAINT = (1 << 0),
   /* for editing in Action Editor */
   GP_FRAME_SELECT = (1 << 1),
+  /* Line Art generation */
+  GP_FRAME_LRT_CLEARED = (1 << 2),
 } eGPDframe_Flag;
 
 /* ***************************************** */
diff --git a/source/blender/makesdna/DNA_lineart_types.h b/source/blender/makesdna/DNA_lineart_types.h
new file mode 100644
index 00000000000..2eb36cfb9d3
--- /dev/null
+++ b/source/blender/makesdna/DNA_lineart_types.h
@@ -0,0 +1,70 @@
+/*
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * The Original Code is Copyright (C) 2010 Blender Foundation.
+ * All rights reserved.
+ *
+ * The Original Code is: all of this file.
+ *
+ * Contributor(s): none yet.
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ */
+
+#ifndef __DNA_LRT_TYPES_H__
+#define __DNA_LRT_TYPES_H__
+
+/** \file DNA_lineart_types.h
+ *  \ingroup DNA
+ */
+
+#include "DNA_ID.h"
+#include "DNA_listBase.h"
+
+struct Object;
+struct Material;
+
+/* Notice that we need to have this file although no struct defines.
+ * Edge flags and usage flags are used by with scene/object/gpencil modifier bits, and those values
+ * needs to stay consistent throughout. */
+
+typedef enum eLineartMainFlags {
+  LRT_INTERSECTION_AS_CONTOUR = (1 << 0),
+  LRT_EVERYTHING_AS_CONTOUR = (1 << 1),
+  LRT_ALLOW_DUPLI_OBJECTS = (1 << 2),
+  LRT_ALLOW_OVERLAPPING_EDGES = (1 << 3),
+  LRT_ALLOW_CLIPPING_BOUNDARIES = (1 << 4),
+  LRT_REMOVE_DOUBLES = (1 << 5),
+} eLineartMainFlags;
+
+typedef enum eLineartEdgeFlag {
+  LRT_EDGE_FLAG_EDGE_MARK = (1 << 0),
+  LRT_EDGE_FLAG_CONTOUR = (1 << 1),
+  LRT_EDGE_FLAG_CREASE = (1 << 2),
+  LRT_EDGE_FLAG_MATERIAL = (1 << 3),
+  LRT_EDGE_FLAG_INTERSECTION = (1 << 4),
+  /**  floating edge, unimplemented yet */
+  LRT_EDGE_FLAG_FLOATING = (1 << 5),
+  /**  also used as discarded line mark */
+  LRT_EDGE_FLAG_CHAIN_PICKED = (1 << 6),
+  LRT_EDGE_FLAG_CLIPPED = (1 << 7),
+  /* Maxed out for 8 bits, DON'T ADD ANYMORE until improvements on the data structure. */
+} eLineartEdgeFlag;
+
+#define LRT_EDGE_FLAG_ALL_TYPE 0x3f
+
+#endif
diff --git a/source/blender/makesdna/DNA_material_types.h b/source/blender/makesdna/DNA_material_types.h
index 884c2df6480..55d5ea202f7 100644
--- a/source/blender/makesdna/DNA_material_types.h
+++ b/source/blender/makesdna/DNA_material_types.h
@@ -145,6 +145,16 @@ typedef enum eMaterialGPencilStyle_Mode {
   GP_MATERIAL_MODE_SQUARE = 2,
 } eMaterialGPencilStyle_Mode;
 
+typedef struct MaterialLineArt {
+  int flags; /* eMaterialLineArtFlags */
+  unsigned char transparency_mask;
+  unsigned char _pad[3];
+} MaterialLineArt;
+
+typedef enum eMaterialLineArtFlags {
+  LRT_MATERIAL_TRANSPARENCY_ENABLED = (1 << 0),
+} eMaterialLineArtFlags;
+
 typedef struct Material {
   ID id;
   /** Animation data (must be immediately after id for utilities to use it). */
@@ -210,6 +220,7 @@ typedef struct Material {
 
   /** Grease pencil color. */
   struct MaterialGPencilStyle *gp_style;
+  struct MaterialLineArt lineart;
 } Material;
 
 /* **************** MATERIAL ********************* */
diff --git a/source/blender/makesdna/DNA_object_defaults.h b/source/blender/makesdna/DNA_object_defaults.h
index 1bca572b963..d545b7912c0 100644
--- a/source/blender/makesdna/DNA_object_defaults.h
+++ b/source/blender/makesdna/DNA_object_defaults.h
@@ -66,6 +66,7 @@
     .preview = NULL, \
     .duplicator_visibility_flag = OB_DUPLI_FLAG_VIEWPORT | OB_DUPLI_FLAG_RENDER, \
     .pc_ids = {NULL, NULL}, \
+    .lineart = { .crease_threshold = DEG2RAD(140.0f) }, \
   }
 
 /** \} */
diff --git a/source/blender/makesdna/DNA_object_types.h b/source/blender/makesdna/DNA_object_types.h
index f6372a0c240..fa4e3953f5b 100644
--- a/source/blender/makesdna/DNA_object_types.h
+++ b/source/blender/makesdna/DNA_object_types.h
@@ -26,6 +26,11 @@
 
 #include "DNA_object_enums.h"
 
+#include "DNA_customdata_types.h"
+#include "DNA_defs.h"
+#include "DNA_lineart_types.h"
+#include "DNA_listBase.h"
+
 #include "DNA_ID.h"
 #include "DNA_action_types.h" /* bAnimVizSettings */
 #include "DNA_customdata_types.h"
@@ -200,6 +205,27 @@ typedef struct Object_Runtime {
   short _pad2[3];
 } Object_Runtime;
 
+typedef struct ObjectLineArt {
+  short usage;
+  short flags;
+
+  /** if OBJECT_LRT_OWN_CREASE is set */
+  float crease_threshold;
+} ObjectLineArt;
+
+enum ObjectFeatureLine_Usage {
+  OBJECT_LRT_INHERENT = 0,
+  OBJECT_LRT_INCLUDE = (1 << 0),
+  OBJECT_LRT_OCCLUSION_ONLY = (1 << 1),
+  OBJECT_LRT_EXCLUDE = (1 << 2),
+  OBJECT_LRT_INTERSECTION_ONLY = (1 << 3),
+  OBJECT_LRT_NO_INTERSECTION = (1 << 4),
+};
+
+enum ObjectFeatureLine_Flags {
+  OBJECT_LRT_OWN_CREASE = (1 << 0),
+};
+
 typedef struct Object {
   ID id;
   /** Animation data (must be immediately after id for utilities to use it). */
@@ -405,6 +431,8 @@ typedef struct Object {
 
   struct PreviewImage *preview;
 
+  ObjectLineArt lineart;
+
   /** Runtime evaluation data (keep last). */
   Object_Runtime runtime;
 } Object;
@@ -595,6 +623,9 @@ enum {
   GP_EMPTY = 0,
   GP_STROKE = 1,
   GP_MONKEY = 2,
+  GP_LRT_SCENE = 3,
+  GP_LRT_OBJECT = 4,
+  GP_LRT_COLLECTION = 5,
 };
 
 /* boundtype */
diff --git a/source/blender/makesdna/DNA_space_types.h b/source/blender/makesdna/DNA_space_types.h
index de9b842312c..755010cd8a5 100644
--- a/source/blender/makesdna/DNA_space_types.h
+++ b/source/blender/makesdna/DNA_space_types.h
@@ -228,6 +228,7 @@ typedef enum eSpaceButtons_Context {
   BCONTEXT_TOOL = 14,
   BCONTEXT_SHADERFX = 15,
   BCONTEXT_OUTPUT = 16,
+  BCONTEXT_COLLECTION = 17,
 
   /* Keep last. */
   BCONTEXT_TOT,
diff --git a/source/blender/makesdna/intern/dna_defaults.c b/source/blender/makesdna/intern/dna_defaults.c
index 7aca742a8e6..95272fb7804 100644
--- a/source/blender/makesdna/intern/dna_defaults.c
+++ b/source/blender/makesdna/intern/dna_defaults.c
@@ -315,6 +315,7 @@ SDNA_DEFAULT_DECL_STRUCT(TextureGpencilModifierData);
 SDNA_DEFAULT_DECL_STRUCT(ThickGpencilModifierData);
 SDNA_DEFAULT_DECL_STRUCT(TimeGpencilModifierData);
 SDNA_DEFAULT_DECL_STRUCT(TintGpencilModifierData);
+SDNA_DEFAULT_DECL_STRUCT(LineartGpencilModifierData);
 
 #undef SDNA_DEFAULT_DECL_STRUCT
 
@@ -539,6 +540,7 @@ const void *DNA_default_table[SDNA_TYPE_MAX] = {
     SDNA_DEFAULT_DECL(ThickGpencilModifierData),
     SDNA_DEFAULT_DECL(TimeGpencilModifierData),
     SDNA_DEFAULT_DECL(TintGpencilModifierData),
+    SDNA_DEFAULT_DECL(LineartGpencilModifierData),
 };
 #undef SDNA_DEFAULT_DECL
 #undef SDNA_DEFAULT_DECL_EX
diff --git a/source/blender/makesdna/intern/makesdna.c b/source/blender/makesdna/intern/makesdna.c
index 7624649bf78..26fc56cfa1d 100644
--- a/source/blender/makesdna/intern/makesdna.c
+++ b/source/blender/makesdna/intern/makesdna.c
@@ -84,6 +84,7 @@ static const char *includefiles[] = {
     "DNA_mesh_types.h",
     "DNA_meshdata_types.h",
     "DNA_modifier_types.h",
+    "DNA_lineart_types.h",
     "DNA_lattice_types.h",
     "DNA_object_types.h",
     "DNA_object_force_types.h",
@@ -1558,6 +1559,7 @@ int main(int argc, char **argv)
 #include "DNA_layer_types.h"
 #include "DNA_light_types.h"
 #include "DNA_lightprobe_types.h"
+#include "DNA_lineart_types.h"
 #include "DNA_linestyle_types.h"
 #include "DNA_listBase.h"
 #include "DNA_mask_types.h"