GP: Mew Merge Strokes operator

This operator allows to create a new stroke joining several selected points of different strokes.

The new stroke will use the current material.

To use, first select the points to be merged. Optionally can remove the old points and strokes.

The operator is available in Edit mode in the Specials menu and Stroke menu.

4 files changed, 580 insertions, 0 deletions

diff --git a/source/blender/editors/gpencil/CMakeLists.txt b/source/blender/editors/gpencil/CMakeLists.txt
index cea2e5d4269..576e16077d2 100644
--- a/source/blender/editors/gpencil/CMakeLists.txt
+++ b/source/blender/editors/gpencil/CMakeLists.txt
@@ -49,6 +49,7 @@ set(SRC
 	gpencil_convert.c
 	gpencil_data.c
 	gpencil_edit.c
+	gpencil_merge.c
 	gpencil_interpolate.c
 	gpencil_primitive.c
 	gpencil_ops.c
diff --git a/source/blender/editors/gpencil/gpencil_intern.h b/source/blender/editors/gpencil/gpencil_intern.h
index aaeb2603acc..6ce1d71db83 100644
--- a/source/blender/editors/gpencil/gpencil_intern.h
+++ b/source/blender/editors/gpencil/gpencil_intern.h
@@ -388,6 +388,10 @@ enum {
 	GP_STROKE_CURVE = 4
 };
 
+enum {
+	GP_MERGE_STROKE = -1,
+	GP_MERGE_POINT = 1
+};
 
 void GPENCIL_OT_stroke_arrange(struct wmOperatorType *ot);
 void GPENCIL_OT_stroke_change_color(struct wmOperatorType *ot);
@@ -402,6 +406,7 @@ void GPENCIL_OT_stroke_simplify_fixed(struct wmOperatorType *ot);
 void GPENCIL_OT_stroke_separate(struct wmOperatorType *ot);
 void GPENCIL_OT_stroke_split(struct wmOperatorType *ot);
 void GPENCIL_OT_stroke_smooth(struct wmOperatorType *ot);
+void GPENCIL_OT_stroke_merge(struct wmOperatorType *ot);
 
 void GPENCIL_OT_brush_presets_create(struct wmOperatorType *ot);
 
diff --git a/source/blender/editors/gpencil/gpencil_merge.c b/source/blender/editors/gpencil/gpencil_merge.c
new file mode 100644
index 00000000000..02f71b19398
--- /dev/null
+++ b/source/blender/editors/gpencil/gpencil_merge.c
@@ -0,0 +1,573 @@
+/*
+ * ***** 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) 2019, Blender Foundation.
+ * This is a new part of Blender
+ *
+ * Contributor(s): Antonio Vazquez
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ *
+ * Operators for merge Grease Pencil strokes
+ */
+
+ /** \file blender/editors/gpencil/gpencil_merge.c
+  *  \ingroup edgpencil
+  */
+
+
+#include <stdio.h>
+
+#include "MEM_guardedalloc.h"
+
+#include "BLI_blenlib.h"
+#include "BLI_ghash.h"
+#include "BLI_math.h"
+
+#include "DNA_gpencil_types.h"
+
+#include "BKE_brush.h"
+#include "BKE_context.h"
+#include "BKE_gpencil.h"
+#include "BKE_material.h"
+
+#include "WM_api.h"
+#include "WM_types.h"
+
+#include "RNA_access.h"
+#include "RNA_define.h"
+
+#include "ED_gpencil.h"
+#include "ED_object.h"
+#include "ED_screen.h"
+#include "ED_view3d.h"
+
+#include "DEG_depsgraph.h"
+#include "DEG_depsgraph_query.h"
+
+#include "gpencil_intern.h"
+
+typedef struct tGPencilPointCache {
+	float factor;  /* value to sort */
+	bGPDstroke *gps;
+	float x, y, z;
+	float pressure;
+	float strength;
+} tGPencilPointCache;
+
+/* helper function to sort points */
+static int gpencil_sort_points(const void *a1, const void *a2)
+{
+	const tGPencilPointCache *ps1 = a1, *ps2 = a2;
+
+	if (ps1->factor < ps2->factor) return -1;
+	else if (ps1->factor > ps2->factor) return 1;
+
+	return 0;
+}
+
+static void gpencil_insert_points_to_stroke(
+	bGPDstroke *gps, tGPencilPointCache *points_array, int totpoints)
+{
+	tGPencilPointCache *point_elem = NULL;
+
+	for (int i = 0; i < totpoints; i++) {
+		point_elem = &points_array[i];
+		bGPDspoint *pt_dst = &gps->points[i];
+
+		copy_v3_v3(&pt_dst->x, &point_elem->x);
+		pt_dst->pressure = point_elem->pressure;
+		pt_dst->strength = point_elem->strength;
+		pt_dst->uv_fac = 1.0f;
+		pt_dst->uv_rot = 0;
+		pt_dst->flag |= GP_SPOINT_SELECT;
+	}
+
+}
+
+static bGPDstroke *gpencil_prepare_stroke(bContext *C, wmOperator *op, int totpoints)
+{
+	ToolSettings *ts = CTX_data_tool_settings(C);
+	Depsgraph *depsgraph = CTX_data_depsgraph(C);
+	Object *ob = CTX_data_active_object(C);
+	bGPDlayer *gpl = CTX_data_active_gpencil_layer(C);
+
+	int cfra_eval = (int)DEG_get_ctime(depsgraph);
+
+	const bool back = RNA_boolean_get(op->ptr, "back");
+	const bool additive = RNA_boolean_get(op->ptr, "additive");
+	const bool cyclic = RNA_boolean_get(op->ptr, "cyclic");
+
+	Paint *paint = &ts->gp_paint->paint;
+	/* if not exist, create a new one */
+	if (paint->brush == NULL) {
+		/* create new brushes */
+		BKE_brush_gpencil_presets(C);
+	}
+	Brush *brush = paint->brush;
+
+	/* frame */
+	short add_frame_mode;
+	if (additive) {
+		add_frame_mode = GP_GETFRAME_ADD_COPY;
+	}
+	else {
+		add_frame_mode = GP_GETFRAME_ADD_NEW;
+	}
+	bGPDframe *gpf = BKE_gpencil_layer_getframe(gpl, cfra_eval, add_frame_mode);
+
+	/* stroke */
+	bGPDstroke *gps = MEM_callocN(sizeof(bGPDstroke), "gp_stroke");
+	gps->totpoints = totpoints;
+	gps->inittime = 0.0f;
+	gps->thickness = brush->size;
+	gps->flag |= GP_STROKE_SELECT;
+	gps->flag |= GP_STROKE_3DSPACE;
+	gps->mat_nr = ob->actcol - 1;
+
+	/* allocate memory for points */
+	gps->points = MEM_callocN(sizeof(bGPDspoint) * totpoints, "gp_stroke_points");
+	/* initialize triangle memory to dummy data */
+	gps->tot_triangles = 0;
+	gps->triangles = NULL;
+	gps->flag |= GP_STROKE_RECALC_GEOMETRY;
+
+	if (cyclic) {
+		gps->flag |= GP_STROKE_CYCLIC;
+	}
+
+	/* add new stroke to frame */
+	if (back) {
+		BLI_addhead(&gpf->strokes, gps);
+	}
+	else {
+		BLI_addtail(&gpf->strokes, gps);
+	}
+
+	return gps;
+}
+
+static void gpencil_get_elements_len(bContext *C, int *totstrokes, int *totpoints)
+{
+	bGPDspoint *pt;
+	int i;
+
+	/* count number of strokes and selected points */
+	CTX_DATA_BEGIN(C, bGPDstroke *, gps, editable_gpencil_strokes)
+	{
+		if (gps->flag & GP_STROKE_SELECT) {
+			*totstrokes += 1;
+			for (i = 0, pt = gps->points; i < gps->totpoints; i++, pt++) {
+				if (pt->flag & GP_SPOINT_SELECT) {
+					*totpoints += 1;
+				}
+			}
+		}
+	}
+	CTX_DATA_END;
+}
+
+static void gpencil_dissolve_points(bContext *C)
+{
+	bGPDstroke *gps, *gpsn;
+
+	CTX_DATA_BEGIN(C, bGPDlayer *, gpl, editable_gpencil_layers)
+	{
+		bGPDframe *gpf = gpl->actframe;
+		if (gpf == NULL) {
+			continue;
+		}
+
+		for (gps = gpf->strokes.first; gps; gps = gpsn) {
+			gpsn = gps->next;
+			gp_stroke_delete_tagged_points(gpf, gps, gpsn, GP_SPOINT_TAG, false);
+		}
+	}
+	CTX_DATA_END;
+}
+
+/* Calc a factor of each selected point and fill an array with all the data.
+ *
+ * The factor is calculated using an imaginary circle, using the angle relative
+ * to this circle and the distance to the calculated center of the selected points.
+ *
+ * All the data is saved to be sorted and used later.
+ */
+static void gpencil_calc_points_factor(
+			bContext *C, const int mode, int totpoints,
+			const bool clear_point, const bool clear_stroke,
+			tGPencilPointCache *src_array)
+{
+	bGPDspoint *pt;
+	int i;
+	int idx = 0;
+
+	/* create selected point array an fill it */
+	bGPDstroke **gps_array = MEM_callocN(sizeof(bGPDstroke *) * totpoints, __func__);
+	bGPDspoint *pt_array = MEM_callocN(sizeof(bGPDspoint) * totpoints, __func__);
+
+	CTX_DATA_BEGIN(C, bGPDlayer *, gpl, editable_gpencil_layers)
+	{
+		bGPDframe *gpf = gpl->actframe;
+		if (gpf == NULL) {
+			continue;
+		}
+		for (bGPDstroke *gps = gpf->strokes.first; gps; gps = gps->next) {
+			if (gps->flag & GP_STROKE_SELECT) {
+				for (i = 0, pt = gps->points; i < gps->totpoints; i++, pt++) {
+					if (clear_stroke) {
+						pt->flag |= GP_SPOINT_TAG;
+					}
+					else {
+						pt->flag &= ~GP_SPOINT_TAG;
+					}
+
+					if (pt->flag & GP_SPOINT_SELECT) {
+						bGPDspoint *pt2 = &pt_array[idx];
+						copy_v3_v3(&pt2->x, &pt->x);
+						pt2->pressure = pt->pressure;
+						pt2->strength = pt->strength;
+						pt->flag &= ~GP_SPOINT_SELECT;
+						if (clear_point) {
+							pt->flag |= GP_SPOINT_TAG;
+						}
+
+						/* save stroke */
+						gps_array[idx] = gps;
+
+						idx++;
+					}
+				}
+				gps->flag &= ~GP_STROKE_SELECT;
+			}
+		}
+	}
+	CTX_DATA_END;
+
+	/* project in 2d plane */
+	int direction = 0;
+	float(*points2d)[2] = MEM_mallocN(sizeof(*points2d) * totpoints, "GP Stroke temp 2d points");
+	BKE_gpencil_stroke_2d_flat(pt_array, totpoints, points2d, &direction);
+
+	/* calc center */
+	float center[2] = { 0.0f, 0.0f };
+	for (i = 0; i < totpoints; i++) {
+		center[0] += points2d[i][0];
+		center[1] += points2d[i][1];
+	}
+	mul_v2_fl(center, 1.0f / totpoints);
+
+	/* calc angle and distance to center for each point */
+	const float axis[2] = { 1.0f, 0.0f };
+	float v1[3];
+	for (i = 0; i < totpoints; i++) {
+		float ln = len_v2v2(center, points2d[i]);
+		sub_v2_v2v2(v1, points2d[i], center);
+		float angle = angle_signed_v2v2(axis, v1);
+		if (angle < 0.0f) {
+			angle = fabsf(angle);
+		}
+		else {
+			angle = (M_PI * 2.0) - angle;
+		}
+		tGPencilPointCache *sort_pt = &src_array[i];
+		bGPDspoint *pt2 = &pt_array[i];
+
+		copy_v3_v3(&sort_pt->x, &pt2->x);
+		sort_pt->pressure = pt2->pressure;
+		sort_pt->strength = pt2->strength;
+
+		sort_pt->gps = gps_array[i];
+
+		if (mode == GP_MERGE_STROKE) {
+			sort_pt->factor = angle;
+		}
+		else {
+			sort_pt->factor = (angle * 100000.0f) + ln;
+		}
+	}
+	MEM_SAFE_FREE(points2d);
+	MEM_SAFE_FREE(gps_array);
+	MEM_SAFE_FREE(pt_array);
+}
+
+/* insert a group of points in destination array */
+static int gpencil_insert_to_array(
+	tGPencilPointCache *src_array, tGPencilPointCache *dst_array, int totpoints,
+	bGPDstroke *gps_filter, bool reverse, int last)
+{
+	tGPencilPointCache *src_elem = NULL;
+	tGPencilPointCache *dst_elem = NULL;
+	int idx = 0;
+
+	for (int i = 0; i < totpoints; i++) {
+		if (!reverse) {
+			idx = i;
+		}
+		else {
+			idx = totpoints - i - 1;
+		}
+		src_elem = &src_array[idx];
+		/* check if all points or only a stroke */
+		if ((gps_filter != NULL) && (gps_filter != src_elem->gps)) {
+			continue;
+		}
+
+		dst_elem = &dst_array[last];
+		last++;
+
+		copy_v3_v3(&dst_elem->x, &src_elem->x);
+		dst_elem->gps = src_elem->gps;
+		dst_elem->pressure = src_elem->pressure;
+		dst_elem->strength = src_elem->strength;
+		dst_elem->factor = src_elem->factor;
+	}
+
+	return last;
+}
+
+/* get first and last point location */
+static void gpencil_get_extremes(
+	tGPencilPointCache *src_array, int totpoints,
+	bGPDstroke *gps_filter, float *start, float *end)
+{
+	tGPencilPointCache *array_pt = NULL;
+	int i;
+
+	/* find first point */
+	for (i = 0; i < totpoints; i++) {
+		array_pt = &src_array[i];
+		if (gps_filter == array_pt->gps) {
+			copy_v3_v3(start, &array_pt->x);
+			break;
+		}
+	}
+	/* find last point */
+	for (i = totpoints - 1; i >= 0; i--) {
+		array_pt = &src_array[i];
+		if (gps_filter == array_pt->gps) {
+			copy_v3_v3(end, &array_pt->x);
+			break;
+		}
+	}
+}
+
+static int gpencil_analyze_strokes(
+		tGPencilPointCache *src_array, int totstrokes, int totpoints,
+		tGPencilPointCache *dst_array)
+{
+		int i;
+		int last = 0;
+		GHash *all_strokes = BLI_ghash_ptr_new(__func__);
+		/* add first stroke to array */
+		tGPencilPointCache *sort_pt = &src_array[0];
+		bGPDstroke *gps = sort_pt->gps;
+		last = gpencil_insert_to_array(src_array, dst_array, totpoints, gps, false, last);
+		float start[3];
+		float end[3];
+		float end_prv[3];
+		gpencil_get_extremes(src_array, totpoints, gps, start, end);
+		copy_v3_v3(end_prv, end);
+		BLI_ghash_insert(all_strokes, sort_pt->gps, sort_pt->gps);
+
+		/* look for near stroke */
+		bool loop = (bool)(totstrokes > 1);
+		while (loop) {
+			bGPDstroke *gps_next = NULL;
+			GHash *strokes = BLI_ghash_ptr_new(__func__);
+			float dist_start = 0.0f;
+			float dist_end = 0.0f;
+			float dist = FLT_MAX;
+			bool reverse = false;
+
+			for (i = 0; i < totpoints; i++) {
+				sort_pt = &src_array[i];
+				/* avoid dups */
+				if (BLI_ghash_haskey(all_strokes, sort_pt->gps)) {
+					continue;
+				}
+				if (!BLI_ghash_haskey(strokes, sort_pt->gps)) {
+					gpencil_get_extremes(src_array, totpoints, sort_pt->gps, start, end);
+					/* distances to previous end */
+					dist_start = len_v3v3(end_prv, start);
+					dist_end = len_v3v3(end_prv, end);
+
+					if (dist > dist_start) {
+						gps_next = sort_pt->gps;
+						dist = dist_start;
+						reverse = false;
+					}
+					if (dist > dist_end) {
+						gps_next = sort_pt->gps;
+						dist = dist_end;
+						reverse = true;
+					}
+					BLI_ghash_insert(strokes, sort_pt->gps, sort_pt->gps);
+				}
+			}
+			BLI_ghash_free(strokes, NULL, NULL);
+
+			/* add the stroke to array */
+			if (gps->next != NULL) {
+				BLI_ghash_insert(all_strokes, gps_next, gps_next);
+				last = gpencil_insert_to_array(src_array, dst_array, totpoints, gps_next, reverse, last);
+				/* replace last end */
+				sort_pt = &dst_array[last - 1];
+				copy_v3_v3(end_prv, &sort_pt->x);
+			}
+
+			/* loop exit */
+			if (last >= totpoints) {
+				loop = false;
+			}
+		}
+
+		BLI_ghash_free(all_strokes, NULL, NULL);
+		return last;
+}
+
+static bool gp_strokes_merge_poll(bContext *C)
+{
+	/* only supported with grease pencil objects */
+	Object *ob = CTX_data_active_object(C);
+	if ((ob == NULL) || (ob->type != OB_GPENCIL)) {
+		return false;
+	}
+
+	/* check material */
+	Material *ma = NULL;
+	ma = give_current_material(ob, ob->actcol);
+	if ((ma == NULL) || (ma->gp_style == NULL)) {
+		return false;
+	}
+
+	/* check hidden or locked materials */
+	MaterialGPencilStyle *gp_style = ma->gp_style;
+	if ((gp_style->flag & GP_STYLE_COLOR_HIDE) ||
+		(gp_style->flag & GP_STYLE_COLOR_LOCKED))
+	{
+		return false;
+	}
+
+	/* check layer */
+	bGPDlayer *gpl = CTX_data_active_gpencil_layer(C);
+	if ((gpl == NULL) ||
+		(gpl->flag & GP_LAYER_LOCKED) ||
+		(gpl->flag & GP_LAYER_HIDE))
+	{
+		return false;
+	}
+
+	/* NOTE: this is a bit slower, but is the most accurate... */
+	return (CTX_DATA_COUNT(C, editable_gpencil_strokes) != 0) && ED_operator_view3d_active(C);
+}
+
+static int gp_stroke_merge_exec(bContext *C, wmOperator *op)
+{
+	const int mode = RNA_enum_get(op->ptr, "mode");
+	const bool clear_point = RNA_boolean_get(op->ptr, "clear_point");
+	const bool clear_stroke = RNA_boolean_get(op->ptr, "clear_stroke");
+
+	Object *ob = CTX_data_active_object(C);
+	/* sanity checks */
+	if (!ob || ob->type != OB_GPENCIL) {
+		return OPERATOR_CANCELLED;
+	}
+
+	bGPdata *gpd = (bGPdata *)ob->data;
+	bGPDlayer *gpl = CTX_data_active_gpencil_layer(C);
+	if (gpl == NULL) {
+		return OPERATOR_CANCELLED;
+	}
+
+	int totstrokes = 0;
+	int totpoints = 0;
+
+	/* count number of strokes and selected points */
+	gpencil_get_elements_len(C, &totstrokes, &totpoints);
+
+	if (totpoints == 0) {
+		return OPERATOR_CANCELLED;
+	}
+
+	/* calc factor of each point and fill an array with all data */
+	tGPencilPointCache *sorted_array = NULL;
+	tGPencilPointCache *original_array = MEM_callocN(sizeof(tGPencilPointCache) * totpoints, __func__);
+	gpencil_calc_points_factor(C, mode, totpoints, clear_point, clear_stroke, original_array);
+
+	/* for strokes analyze strokes and load sorted array */
+	if (mode == GP_MERGE_STROKE) {
+		sorted_array = MEM_callocN(sizeof(tGPencilPointCache) * totpoints, __func__);
+		totpoints = gpencil_analyze_strokes(original_array, totstrokes, totpoints, sorted_array);
+	}
+	else {
+		/* make a copy to sort */
+		sorted_array = MEM_dupallocN(original_array);
+		/* sort by factor around center */
+		qsort(sorted_array, totpoints, sizeof(tGPencilPointCache), gpencil_sort_points);
+	}
+
+	/* prepare the new stroke */
+	bGPDstroke *gps = gpencil_prepare_stroke(C, op, totpoints);
+	
+	/* copy original points to final stroke */
+	gpencil_insert_points_to_stroke(gps, sorted_array, totpoints);
+
+	/* dissolve all tagged points */
+	if ((clear_point) || (clear_stroke)) {
+		gpencil_dissolve_points(C);
+	}
+
+	/* free memory */
+	MEM_SAFE_FREE(original_array);
+	MEM_SAFE_FREE(sorted_array);
+
+	/* notifiers */
+	DEG_id_tag_update(&gpd->id, ID_RECALC_TRANSFORM | ID_RECALC_GEOMETRY);
+	WM_event_add_notifier(C, NC_GPENCIL | ND_DATA | NA_EDITED, NULL);
+
+	return OPERATOR_FINISHED;
+}
+
+void GPENCIL_OT_stroke_merge(wmOperatorType *ot)
+{
+	static const EnumPropertyItem mode_type[] = {
+		{GP_MERGE_STROKE, "STROKE", 0, "Stroke", ""},
+		{GP_MERGE_POINT, "POINT", 0, "Point", ""},
+		{0, NULL, 0, NULL, NULL}
+	};
+
+	/* identifiers */
+	ot->name = "Merge Strokes";
+	ot->idname = "GPENCIL_OT_stroke_merge";
+	ot->description = "Create a new stroke with the selected stroke points";
+
+	/* api callbacks */
+	ot->exec = gp_stroke_merge_exec;
+	ot->poll = gp_strokes_merge_poll;
+
+	/* flags */
+	ot->flag = OPTYPE_REGISTER | OPTYPE_UNDO;
+
+	/* properties */
+	ot->prop = RNA_def_enum(ot->srna, "mode", mode_type, GP_MERGE_STROKE, "Mode", "");
+	RNA_def_boolean(ot->srna, "back", 0, "Draw on Back", "Draw new stroke below all previous strokes");
+	RNA_def_boolean(ot->srna, "additive", 0, "Additive Drawing", "Add to previous drawing");
+	RNA_def_boolean(ot->srna, "cyclic", 0, "Cyclic", "Close new stroke");
+	RNA_def_boolean(ot->srna, "clear_point", 0, "Dissolve Points", "Dissolve old selected points");
+	RNA_def_boolean(ot->srna, "clear_stroke", 0, "Delete Strokes", "Delete old selected strokes");
+}
diff --git a/source/blender/editors/gpencil/gpencil_ops.c b/source/blender/editors/gpencil/gpencil_ops.c
index 3eaf72121a8..7814aa963ba 100644
--- a/source/blender/editors/gpencil/gpencil_ops.c
+++ b/source/blender/editors/gpencil/gpencil_ops.c
@@ -309,6 +309,7 @@ void ED_operatortypes_gpencil(void)
 	WM_operatortype_append(GPENCIL_OT_stroke_separate);
 	WM_operatortype_append(GPENCIL_OT_stroke_split);
 	WM_operatortype_append(GPENCIL_OT_stroke_smooth);
+	WM_operatortype_append(GPENCIL_OT_stroke_merge);
 
 	WM_operatortype_append(GPENCIL_OT_brush_presets_create);