bugfix [#24291] Error parenting a child with any negative scaling coordinate

the bug was in object_apply_mat4(), caused by applying a non-normalized matrix to the rotation.
Blender 2.4x also had this problem, surprising nobody noticed!.

3 files changed, 37 insertions, 16 deletions

diff --git a/source/blender/blenkernel/intern/object.c b/source/blender/blenkernel/intern/object.c
index 17e488c8353..79030e3adfa 100644
--- a/source/blender/blenkernel/intern/object.c
+++ b/source/blender/blenkernel/intern/object.c
@@ -1698,29 +1698,28 @@ void object_mat3_to_rot(Object *ob, float mat[][3], int use_compat)
 /* see pchan_apply_mat4() for the equivalent 'pchan' function */
 void object_apply_mat4(Object *ob, float mat[][4])
 {
-	float mat3[3][3], tmat[3][3], imat[3][3];
+	float mat3[3][3];    /* obmat -> 3x3 */
+	float mat3_n[3][3];  /* obmat -> normalized, 3x3 */
+	float imat3_n[3][3]; /* obmat -> normalized & inverted, 3x3 */
 
 	/* location */
 	copy_v3_v3(ob->loc, mat[3]);
 	
 	/* rotation */
 	copy_m3_m4(mat3, mat);
-	object_mat3_to_rot(ob, mat3, 0);
-	
+	/* so scale doesnt interfear with rotation [#24291] */
+	normalize_m3_m3(mat3_n, mat3);
+
+	object_mat3_to_rot(ob, mat3_n, 0);
+
 	/* scale */
-#if 0
-	/* works fine except for neg scales */
-	mat4_to_size(ob->size, mat);
-#else
-	/* this is more complicated but works for negative scales */
-	object_rot_to_mat3(ob, tmat);
-	invert_m3_m3(imat, tmat);
-	mul_m3_m3m3(tmat, imat, mat3);
-
-	ob->size[0]= tmat[0][0];
-	ob->size[1]= tmat[1][1];
-	ob->size[2]= tmat[2][2];
-#endif
+	/* note: mat4_to_size(ob->size, mat) fails for negative scale */
+	invert_m3_m3(imat3_n, mat3_n);
+	mul_m3_m3m3(mat3, imat3_n, mat3);
+
+	ob->size[0]= mat3[0][0];
+	ob->size[1]= mat3[1][1];
+	ob->size[2]= mat3[2][2];
 }
 
 void object_to_mat3(Object *ob, float mat[][3])	/* no parent */
diff --git a/source/blender/blenlib/BLI_math_matrix.h b/source/blender/blenlib/BLI_math_matrix.h
index 77ebcb24975..294546bb222 100644
--- a/source/blender/blenlib/BLI_math_matrix.h
+++ b/source/blender/blenlib/BLI_math_matrix.h
@@ -102,7 +102,9 @@ void transpose_m3(float R[3][3]);
 void transpose_m4(float R[4][4]);
 
 void normalize_m3(float R[3][3]);
+void normalize_m3_m3(float R[3][3], float A[3][3]);
 void normalize_m4(float R[4][4]);
+void normalize_m4_m4(float R[4][4], float A[4][4]);
 
 void orthogonalize_m3(float R[3][3], int axis);
 void orthogonalize_m4(float R[4][4], int axis);
diff --git a/source/blender/blenlib/intern/math_matrix.c b/source/blender/blenlib/intern/math_matrix.c
index 3b5ffa2d442..197d3676367 100644
--- a/source/blender/blenlib/intern/math_matrix.c
+++ b/source/blender/blenlib/intern/math_matrix.c
@@ -750,6 +750,14 @@ void normalize_m3(float mat[][3])
 	normalize_v3(mat[2]);
 }
 
+void normalize_m3_m3(float rmat[][3], float mat[][3])
+{	
+	normalize_v3_v3(rmat[0], mat[0]);
+	normalize_v3_v3(rmat[1], mat[1]);
+	normalize_v3_v3(rmat[2], mat[2]);
+}
+
+
 void normalize_m4(float mat[][4])
 {
 	float len;
@@ -762,6 +770,18 @@ void normalize_m4(float mat[][4])
 	if(len!=0.0) mat[2][3]/= len;
 }
 
+void normalize_m4_m4(float rmat[][4], float mat[][4])
+{
+	float len;
+	
+	len= normalize_v3_v3(rmat[0], mat[0]);
+	if(len!=0.0) rmat[0][3]= mat[0][3] / len;
+	len= normalize_v3_v3(rmat[1], mat[1]);
+	if(len!=0.0) rmat[1][3]= mat[1][3] / len;
+	len= normalize_v3_v3(rmat[2], mat[2]);
+	if(len!=0.0) rmat[2][3]= mat[2][3] / len;;
+}
+
 void adjoint_m3_m3(float m1[][3], float m[][3])
 {
 	m1[0][0]=m[1][1]*m[2][2]-m[1][2]*m[2][1];