[Bf-blender-cvs] [74260a2b6da] master: BMesh: Add BM_face_calc_area_uv

[Clément Foucault]

Commit: 74260a2b6da86e3f6da0a37afc6d47338c1be034
Author: Clément Foucault
Date:   Wed Jan 9 22:09:27 2019 +0100
Branches: master
https://developer.blender.org/rB74260a2b6da86e3f6da0a37afc6d47338c1be034

BMesh: Add BM_face_calc_area_uv

===================================================================

M	source/blender/bmesh/intern/bmesh_polygon.c
M	source/blender/bmesh/intern/bmesh_polygon.h

===================================================================

diff --git a/source/blender/bmesh/intern/bmesh_polygon.c b/source/blender/bmesh/intern/bmesh_polygon.c
index 87903b3fd58..a3b0f72fbcf 100644
--- a/source/blender/bmesh/intern/bmesh_polygon.c
+++ b/source/blender/bmesh/intern/bmesh_polygon.c
@@ -30,6 +30,7 @@
 
 #include "DNA_listBase.h"
 #include "DNA_modifier_types.h"
+#include "DNA_meshdata_types.h"
 
 #include "MEM_guardedalloc.h"
 
@@ -261,6 +262,25 @@ float BM_face_calc_area_with_mat3(const BMFace *f, const float mat3[3][3])
 	return len_v3(n) * 0.5f;
 }
 
+/**
+ * get the area of UV face
+ */
+float BM_face_calc_area_uv(const BMFace *f, int cd_loop_uv_offset)
+{
+	/* inline 'area_poly_v2' logic, avoid creating a temp array */
+	const BMLoop *l_iter, *l_first;
+
+	l_iter = l_first = BM_FACE_FIRST_LOOP(f);
+	/* The Trapezium Area Rule */
+	float cross = 0.0f;
+	do {
+		const MLoopUV *luv = BM_ELEM_CD_GET_VOID_P(l_iter, cd_loop_uv_offset);
+		const MLoopUV *luv_next = BM_ELEM_CD_GET_VOID_P(l_iter->next, cd_loop_uv_offset);
+		cross += (luv_next->uv[0] - luv->uv[0]) * (luv_next->uv[1] + luv->uv[1]);
+	} while ((l_iter = l_iter->next) != l_first);
+	return fabsf(cross * 0.5f);
+}
+
 /**
  * compute the perimeter of an ngon
  */
diff --git a/source/blender/bmesh/intern/bmesh_polygon.h b/source/blender/bmesh/intern/bmesh_polygon.h
index 2003f2d2503..8033187c10b 100644
--- a/source/blender/bmesh/intern/bmesh_polygon.h
+++ b/source/blender/bmesh/intern/bmesh_polygon.h
@@ -45,6 +45,7 @@ float BM_face_calc_normal_vcos(
 float BM_face_calc_normal_subset(const BMLoop *l_first, const BMLoop *l_last, float r_no[3]) ATTR_NONNULL();
 float BM_face_calc_area(const BMFace *f) ATTR_WARN_UNUSED_RESULT ATTR_NONNULL();
 float BM_face_calc_area_with_mat3(const BMFace *f, const float mat3[3][3]) ATTR_WARN_UNUSED_RESULT ATTR_NONNULL();
+float BM_face_calc_area_uv(const BMFace *f, int cd_loop_uv_offset) ATTR_WARN_UNUSED_RESULT ATTR_NONNULL();
 float BM_face_calc_perimeter(const BMFace *f) ATTR_WARN_UNUSED_RESULT ATTR_NONNULL();
 float BM_face_calc_perimeter_with_mat3(const BMFace *f, const float mat3[3][3]) ATTR_WARN_UNUSED_RESULT ATTR_NONNULL();
 void  BM_face_calc_tangent_edge(const BMFace *f, float r_plane[3]) ATTR_NONNULL();