Fix stupid handling of 'Object.matrix_local' in RNA.

The getter of this matrix (actually, `BKE_object_matrix_local_get()`) was only correct
in case of pure-object parenting, bone parenting and such did not gave valid results.

Also cleaned up a bit setter code, was using as temp storage ob->obmat itself,
which is supposed to be a world matrix!

Reviewers: campbellbarton

Reviewed By: campbellbarton

Differential Revision: https://developer.blender.org/D958

3 files changed, 15 insertions, 11 deletions

diff --git a/source/blender/blenkernel/intern/object.c b/source/blender/blenkernel/intern/object.c
index 1676f22683a..f6b328eb8e8 100644
--- a/source/blender/blenkernel/intern/object.c
+++ b/source/blender/blenkernel/intern/object.c
@@ -2019,12 +2019,16 @@ void BKE_object_to_mat4(Object *ob, float mat[4][4])
 	add_v3_v3v3(mat[3], ob->loc, ob->dloc);
 }
 
+static void ob_get_parent_matrix(Scene *scene, Object *ob, Object *par, float parentmat[4][4]);
+
 void BKE_object_matrix_local_get(struct Object *ob, float mat[4][4])
 {
 	if (ob->parent) {
-		float invmat[4][4]; /* for inverse of parent's matrix */
-		invert_m4_m4(invmat, ob->parent->obmat);
-		mul_m4_m4m4(mat, invmat, ob->obmat);
+		float par_imat[4][4];
+
+		ob_get_parent_matrix(NULL, ob, ob->parent, par_imat);
+		invert_m4(par_imat);
+		mul_m4_m4m4(mat, par_imat, ob->obmat);
 	}
 	else {
 		copy_m4_m4(mat, ob->obmat);
diff --git a/source/blender/collada/TransformWriter.cpp b/source/blender/collada/TransformWriter.cpp
index 595787b44ac..e205608a365 100644
--- a/source/blender/collada/TransformWriter.cpp
+++ b/source/blender/collada/TransformWriter.cpp
@@ -102,7 +102,7 @@ void TransformWriter::add_node_transform_ob(COLLADASW::Node& node, Object *ob, B
 	double d_obmat[4][4];
 	float  f_obmat[4][4];
 
-	/* Export the local Matrix (relative to the object parent) */
+	/* Export the local Matrix (relative to the object parent, be it an object, bone or vertex(-tices)) */
 	BKE_object_matrix_local_get(ob, f_obmat);
 	converter.mat4_to_dae_double(d_obmat, f_obmat);
 
diff --git a/source/blender/makesrna/intern/rna_object.c b/source/blender/makesrna/intern/rna_object.c
index 9741c75d68f..6c421c82195 100644
--- a/source/blender/makesrna/intern/rna_object.c
+++ b/source/blender/makesrna/intern/rna_object.c
@@ -233,21 +233,21 @@ static void rna_Object_matrix_local_get(PointerRNA *ptr, float values[16])
 static void rna_Object_matrix_local_set(PointerRNA *ptr, const float values[16])
 {
 	Object *ob = ptr->id.data;
+	float local_mat[4][4];
 
-	/* localspace matrix is truly relative to the parent, but parameters
-	 * stored in object are relative to parentinv matrix.  Undo the parent
-	 * inverse part before updating obmat and calling apply_obmat() */
+	/* localspace matrix is truly relative to the parent, but parameters stored in object are
+	 * relative to parentinv matrix. Undo the parent inverse part before applying it as local matrix. */
 	if (ob->parent) {
 		float invmat[4][4];
 		invert_m4_m4(invmat, ob->parentinv);
-		mul_m4_m4m4(ob->obmat, invmat, (float(*)[4])values);
+		mul_m4_m4m4(local_mat, invmat, (float(*)[4])values);
 	}
 	else {
-		copy_m4_m4(ob->obmat, (float(*)[4])values);
+		copy_m4_m4(local_mat, (float(*)[4])values);
 	}
 
-	/* don't use compat so we get predictable rotation */
-	BKE_object_apply_mat4(ob, ob->obmat, false, false);
+	/* don't use compat so we get predictable rotation, and do not use parenting either, because it's a local matrix! */
+	BKE_object_apply_mat4(ob, local_mat, false, false);
 }
 
 static void rna_Object_matrix_basis_get(PointerRNA *ptr, float values[16])