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

1 files changed, 120 insertions, 0 deletions

diff --git a/source/blender/editors/gpencil/gpencil_add_lineart.c b/source/blender/editors/gpencil/gpencil_add_lineart.c
new file mode 100644
index 00000000000..71253635ea8
--- /dev/null
+++ b/source/blender/editors/gpencil/gpencil_add_lineart.c
@@ -0,0 +1,120 @@
+/*
+ * 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) 2017 Blender Foundation
+ * This is a new part of Blender
+ */
+
+/** \file
+ * \ingroup edgpencil
+ */
+
+#include "BLI_math.h"
+#include "BLI_utildefines.h"
+
+#include "DNA_gpencil_types.h"
+#include "DNA_material_types.h"
+#include "DNA_object_types.h"
+#include "DNA_scene_types.h"
+
+#include "BKE_brush.h"
+#include "BKE_context.h"
+#include "BKE_gpencil.h"
+#include "BKE_gpencil_geom.h"
+#include "BKE_lib_id.h"
+#include "BKE_main.h"
+#include "BKE_material.h"
+
+#include "DEG_depsgraph.h"
+#include "DEG_depsgraph_query.h"
+
+#include "ED_gpencil.h"
+
+/* Definition of the most important info from a color */
+typedef struct ColorTemplate {
+  const char *name;
+  float line[4];
+  float fill[4];
+} ColorTemplate;
+
+/* Add color an ensure duplications (matched by name) */
+static int gpencil_lineart_material(Main *bmain,
+                                    Object *ob,
+                                    const ColorTemplate *pct,
+                                    const bool fill)
+{
+  short *totcol = BKE_object_material_len_p(ob);
+  Material *ma = NULL;
+  for (short i = 0; i < *totcol; i++) {
+    ma = BKE_gpencil_material(ob, i + 1);
+    if (STREQ(ma->id.name, pct->name)) {
+      return i;
+    }
+  }
+
+  int idx;
+
+  /* create a new one */
+  ma = BKE_gpencil_object_material_new(bmain, ob, pct->name, &idx);
+
+  copy_v4_v4(ma->gp_style->stroke_rgba, pct->line);
+  srgb_to_linearrgb_v4(ma->gp_style->stroke_rgba, ma->gp_style->stroke_rgba);
+
+  copy_v4_v4(ma->gp_style->fill_rgba, pct->fill);
+  srgb_to_linearrgb_v4(ma->gp_style->fill_rgba, ma->gp_style->fill_rgba);
+
+  if (fill) {
+    ma->gp_style->flag |= GP_MATERIAL_FILL_SHOW;
+  }
+
+  return idx;
+}
+
+/* ***************************************************************** */
+/* Color Data */
+
+static const ColorTemplate gp_stroke_material_black = {
+    "Black",
+    {0.0f, 0.0f, 0.0f, 1.0f},
+    {0.0f, 0.0f, 0.0f, 0.0f},
+};
+
+/* ***************************************************************** */
+/* LineArt API */
+
+/* Add a Simple LineArt setup. */
+void ED_gpencil_create_lineart(bContext *C, Object *ob)
+{
+  Main *bmain = CTX_data_main(C);
+  Scene *scene = CTX_data_scene(C);
+  bGPdata *gpd = (bGPdata *)ob->data;
+
+  /* create colors */
+  int color_black = gpencil_lineart_material(bmain, ob, &gp_stroke_material_black, false);
+
+  /* set first color as active and in brushes */
+  ob->actcol = color_black + 1;
+
+  /* layers */
+  bGPDlayer *lines = BKE_gpencil_layer_addnew(gpd, "Lines", true);
+
+  /* frames */
+  BKE_gpencil_frame_addnew(lines, CFRA);
+
+  /* update depsgraph */
+  /* To trigger modifier update, this is still needed although we don't have any strokes. */
+  DEG_id_tag_update(&gpd->id, ID_RECALC_TRANSFORM | ID_RECALC_GEOMETRY);
+  gpd->flag |= GP_DATA_CACHE_IS_DIRTY;
+}