uv-pack operator: option to rotate uv islands to fit in the optimal rectangle when packing.

source/blender/blenlib/BLI_convexhull2d.h

@@ -28,4 +28,6 @@
 int BLI_convexhull_2d_presorted(const float (*points)[2], const int n, int r_points[]);
 int BLI_convexhull_2d(const float (*points)[2], const int n, int r_points[]);
 
+float BLI_convexhull_aabb_fit_2d(const float (*points_hull)[2], unsigned int n);
+
 #endif  /* __BLI_CONVEXHULL2D__ */

source/blender/blenlib/intern/convexhull2d.c

@@ -24,7 +24,7 @@
 #include "MEM_guardedalloc.h"
 
 #include "BLI_convexhull2d.h"
-
+#include "BLI_math.h"
 #include "BLI_strict_flags.h"
 #include "BLI_utildefines.h"
 
@@ -37,6 +37,9 @@
  * http://softsurfer.com/Archive/algorithm_0203/algorithm_0203.htm
  */
 
+/** \name Main Convex-Hull Calculation
+ * \{ */
+
 /**
  * tests if a point is Left|On|Right of an infinite line.
  *    Input:  three points P0, P1, and P2
@@ -219,3 +222,71 @@ int BLI_convexhull_2d(const float (*points)[2], const int n, int r_points[])
 
 	return tot;
 }
+
+/** \} */
+
+
+/* -------------------------------------------------------------------- */
+/* Helper functions */
+
+/** \name Utility Convex-Hull Functions
+ * \{ */
+
+/**
+ * \return The best angle for fitting the convex hull to an axis aligned bounding box.
+ *
+ * Intended to be used with #BLI_convexhull_2d
+ *
+ * \note we could return the index of the best edge too if its needed.
+ */
+float BLI_convexhull_aabb_fit_2d(const float (*points_hull)[2], unsigned int n)
+{
+	unsigned int i, i_prev;
+	float area_best = FLT_MAX;
+	float angle_best = 0.0f;
+
+	i_prev = n - 1;
+	for (i = 0; i < n; i++) {
+		const float *ev_a = points_hull[i];
+		const float *ev_b = points_hull[i_prev];
+		float dvec[2];
+
+		sub_v2_v2v2(dvec, ev_a, ev_b);
+		if (normalize_v2(dvec) != 0.0f) {
+			float mat[2][2];
+			float min[2] = {FLT_MAX, FLT_MAX}, max[2] = {-FLT_MAX, -FLT_MAX};
+
+			unsigned int j;
+			const float angle = atan2f(dvec[0], dvec[1]);
+			float area;
+
+			angle_to_mat2(mat, angle);
+
+			for (j = 0; j < n; j++) {
+				float tvec[2];
+				mul_v2_m2v2(tvec, mat, points_hull[j]);
+
+				min[0] = min_ff(min[0], tvec[0]);
+				min[1] = min_ff(min[1], tvec[1]);
+
+				max[0] = max_ff(max[0], tvec[0]);
+				max[1] = max_ff(max[1], tvec[1]);
+
+				area = (max[0] - min[0]) * (max[1] - min[1]);
+				if (area > area_best) {
+					break;
+				}
+			}
+
+			if (area < area_best) {
+				area_best = area;
+				angle_best = angle;
+			}
+		}
+
+		i_prev = i;
+	}
+
+	return angle_best;
+}
+/** \} */

source/blender/editors/uvedit/uvedit_parametrizer.c

@@ -33,6 +33,7 @@
 #include "BLI_rand.h"
 #include "BLI_heap.h"
 #include "BLI_boxpack2d.h"
+#include "BLI_convexhull2d.h"
 
 #include "ONL_opennl.h"
 
@@ -485,6 +486,36 @@ static void p_chart_uv_translate(PChart *chart, float trans[2])
 	}
 }
 
+static void p_chart_uv_transform(PChart *chart, float mat[2][2])
+{
+	PVert *v;
+
+	for (v = chart->verts; v; v = v->nextlink) {
+		mul_v2_m2v2(v->uv, mat, v->uv);
+	}
+}
+
+static void p_chart_uv_to_array(PChart *chart, float (*points)[2])
+{
+	PVert *v;
+	unsigned int i = 0;
+
+	for (v = chart->verts; v; v = v->nextlink) {
+		copy_v2_v2(points[i++], v->uv);
+	}
+}
+
+static void UNUSED_FUNCTION(p_chart_uv_from_array)(PChart *chart, float (*points)[2])
+{
+	PVert *v;
+	unsigned int i = 0;
+
+	for (v = chart->verts; v; v = v->nextlink) {
+		copy_v2_v2(v->uv, points[i++]);
+	}
+}
+
+
 static PBool p_intersect_line_2d_dir(float *v1, float *dir1, float *v2, float *dir2, float *isect)
 {
 	float lmbda, div;
@@ -4441,8 +4472,59 @@ void param_smooth_area(ParamHandle *handle)
 		p_smooth(chart);
 	}
 }
- 
-void param_pack(ParamHandle *handle, float margin)
+
+/* don't pack, just rotate (used for better packing) */
+static void param_pack_rotate(ParamHandle *handle)
+{
+	PChart *chart;
+	int i;
+
+	PHandle *phandle = (PHandle *)handle;
+
+	for (i = 0; i < phandle->ncharts; i++) {
+		float (*points)[2];
+		int *index_map;
+		int tot;
+
+		chart = phandle->charts[i];
+
+		if (chart->flag & PCHART_NOPACK) {
+			continue;
+		}
+
+		points = MEM_mallocN(sizeof(*points) * chart->nverts, __func__);
+		index_map = MEM_mallocN(sizeof(*index_map) * chart->nverts, __func__);
+
+		p_chart_uv_to_array(chart, points);
+
+		tot = BLI_convexhull_2d((const float (*)[2])points, chart->nverts, index_map);
+
+		if (tot) {
+			float (*points_hull)[2];
+			int j;
+			float angle;
+
+			points_hull = MEM_mallocN(sizeof(*points) * tot, __func__);
+			for (j = 0; j < tot; j++) {
+				copy_v2_v2(points_hull[j], points[index_map[j]]);
+			}
+
+			angle = BLI_convexhull_aabb_fit_2d((const float (*)[2])points_hull, tot);
+			MEM_freeN(points_hull);
+
+			if (angle != 0.0f) {
+				float mat[2][2];
+				angle_to_mat2(mat, angle);
+				p_chart_uv_transform(chart, mat);
+			}
+		}
+
+		MEM_freeN(points);
+		MEM_freeN(index_map);
+	}
+}
+
+void param_pack(ParamHandle *handle, float margin, bool do_rotate)
 {	
 	/* box packing variables */
 	BoxPack *boxarray, *box;
@@ -4461,6 +4543,11 @@ void param_pack(ParamHandle *handle, float margin)
 	if (phandle->aspx != phandle->aspy)
 		param_scale(handle, 1.0f / phandle->aspx, 1.0f / phandle->aspy);
 	
+	/* this could be its own function */
+	if (do_rotate) {
+		param_pack_rotate(handle);
+	}
+
 	/* we may not use all these boxes */
 	boxarray = MEM_mallocN(phandle->ncharts * sizeof(BoxPack), "BoxPack box");
 	

source/blender/editors/uvedit/uvedit_parametrizer.h

@@ -99,7 +99,7 @@ void param_smooth_area(ParamHandle *handle);
 
 /* Packing */
 
-void param_pack(ParamHandle *handle, float margin);
+void param_pack(ParamHandle *handle, float margin, bool do_rotate);
 
 /* Average area for all charts */
 

source/blender/editors/uvedit/uvedit_unwrap_ops.c

@@ -718,6 +718,7 @@ static int pack_islands_exec(bContext *C, wmOperator *op)
 	BMEditMesh *em = BKE_editmesh_from_object(obedit);
 	ParamHandle *handle;
 	bool implicit = true;
+	bool do_rotate = RNA_boolean_get(op->ptr, "rotate");
 
 	if (!uvedit_have_selection(scene, em, implicit)) {
 		return OPERATOR_CANCELLED;
@@ -729,7 +730,7 @@ static int pack_islands_exec(bContext *C, wmOperator *op)
 		RNA_float_set(op->ptr, "margin", scene->toolsettings->uvcalc_margin);
 
 	handle = construct_param_handle(scene, obedit, em, implicit, 0, 1, 1);
-	param_pack(handle, scene->toolsettings->uvcalc_margin);
+	param_pack(handle, scene->toolsettings->uvcalc_margin, do_rotate);
 	param_flush(handle);
 	param_delete(handle);
 	
@@ -753,6 +754,7 @@ void UV_OT_pack_islands(wmOperatorType *ot)
 	ot->poll = ED_operator_uvedit;
 
 	/* properties */
+	RNA_def_boolean(ot->srna, "rotate", true, "Rotate", "Rotate islands for best fit");
 	RNA_def_float_factor(ot->srna, "margin", 0.001f, 0.0f, 1.0f, "Margin", "Space between islands", 0.0f, 1.0f);
 }
 
@@ -1151,7 +1153,7 @@ void ED_unwrap_lscm(Scene *scene, Object *obedit, const short sel)
 	param_lscm_end(handle);
 
 	param_average(handle);
-	param_pack(handle, scene->toolsettings->uvcalc_margin);
+	param_pack(handle, scene->toolsettings->uvcalc_margin, false);
 
 	param_flush(handle);