Refactor: Rename Object->obmat to Object->object_to_world

Motivation is to disambiguate on the naming level what the matrix
actually means. It is very easy to understand the meaning backwards,
especially since in Python the name goes the opposite way (it is
called `world_matrix` in the Python API).

It is important to disambiguate the naming without making developers
to look into the comment in the header file (which is also not super
clear either). Additionally, more clear naming facilitates the unit
verification (or, in this case, space validation) when reading an
expression.

This patch calls the matrix `object_to_world` which makes it clear
from the local code what is it exactly going on. This is only done
on DNA level, and a lot of local variables still follow the old
naming.

A DNA rename is setup in a way that there is no change on the file
level, so there should be no regressions at all.

The possibility is to add `_matrix` or `_mat` suffix to the name
to make it explicit that it is a matrix. Although, not sure if it
really helps the readability, or is it something redundant.

Differential Revision: https://developer.blender.org/D16328

4 files changed, 9 insertions, 8 deletions

diff --git a/source/blender/makesrna/intern/rna_depsgraph.c b/source/blender/makesrna/intern/rna_depsgraph.c
index db5b3c33c59..9af76de2a2b 100644
--- a/source/blender/makesrna/intern/rna_depsgraph.c
+++ b/source/blender/makesrna/intern/rna_depsgraph.c
@@ -168,7 +168,7 @@ static void rna_DepsgraphObjectInstance_matrix_world_get(PointerRNA *ptr, float
     /* We can return actual object's matrix here, no reason to return identity matrix
      * when this is not actually an instance... */
     Object *ob = (Object *)di->iter.current;
-    copy_m4_m4((float(*)[4])mat, ob->obmat);
+    copy_m4_m4((float(*)[4])mat, ob->object_to_world);
   }
 }
 
diff --git a/source/blender/makesrna/intern/rna_gpencil.c b/source/blender/makesrna/intern/rna_gpencil.c
index cf0ff546d41..a55a1b0ffcd 100644
--- a/source/blender/makesrna/intern/rna_gpencil.c
+++ b/source/blender/makesrna/intern/rna_gpencil.c
@@ -334,13 +334,13 @@ static int rna_GPencilLayer_active_frame_editable(PointerRNA *ptr, const char **
 static void set_parent(bGPDlayer *gpl, Object *par, const int type, const char *substr)
 {
   if (type == PAROBJECT) {
-    invert_m4_m4(gpl->inverse, par->obmat);
+    invert_m4_m4(gpl->inverse, par->object_to_world);
     gpl->parent = par;
     gpl->partype |= PAROBJECT;
     gpl->parsubstr[0] = 0;
   }
   else if (type == PARSKEL) {
-    invert_m4_m4(gpl->inverse, par->obmat);
+    invert_m4_m4(gpl->inverse, par->object_to_world);
     gpl->parent = par;
     gpl->partype |= PARSKEL;
     gpl->parsubstr[0] = 0;
@@ -349,7 +349,7 @@ static void set_parent(bGPDlayer *gpl, Object *par, const int type, const char *
     bPoseChannel *pchan = BKE_pose_channel_find_name(par->pose, substr);
     if (pchan) {
       float tmp_mat[4][4];
-      mul_m4_m4m4(tmp_mat, par->obmat, pchan->pose_mat);
+      mul_m4_m4m4(tmp_mat, par->object_to_world, pchan->pose_mat);
 
       invert_m4_m4(gpl->inverse, tmp_mat);
       gpl->parent = par;
@@ -357,7 +357,7 @@ static void set_parent(bGPDlayer *gpl, Object *par, const int type, const char *
       BLI_strncpy(gpl->parsubstr, substr, sizeof(gpl->parsubstr));
     }
     else {
-      invert_m4_m4(gpl->inverse, par->obmat);
+      invert_m4_m4(gpl->inverse, par->object_to_world);
       gpl->parent = par;
       gpl->partype |= PAROBJECT;
       gpl->parsubstr[0] = 0;
diff --git a/source/blender/makesrna/intern/rna_object.c b/source/blender/makesrna/intern/rna_object.c
index 7f4ed39c001..1d6b3d5d69e 100644
--- a/source/blender/makesrna/intern/rna_object.c
+++ b/source/blender/makesrna/intern/rna_object.c
@@ -356,7 +356,8 @@ static void rna_Object_internal_update_draw(Main *UNUSED(bmain),
 static void rna_Object_matrix_world_update(Main *bmain, Scene *scene, PointerRNA *ptr)
 {
   /* don't use compat so we get predictable rotation */
-  BKE_object_apply_mat4((Object *)ptr->owner_id, ((Object *)ptr->owner_id)->obmat, false, true);
+  BKE_object_apply_mat4(
+      (Object *)ptr->owner_id, ((Object *)ptr->owner_id)->object_to_world, false, true);
   rna_Object_internal_update(bmain, scene, ptr);
 }
 
@@ -3390,7 +3391,7 @@ static void rna_def_object(BlenderRNA *brna)
 
   /* matrix */
   prop = RNA_def_property(srna, "matrix_world", PROP_FLOAT, PROP_MATRIX);
-  RNA_def_property_float_sdna(prop, NULL, "obmat");
+  RNA_def_property_float_sdna(prop, NULL, "object_to_world");
   RNA_def_property_multi_array(prop, 2, rna_matrix_dimsize_4x4);
   RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);
   RNA_def_property_override_flag(prop, PROPOVERRIDE_NO_COMPARISON);
diff --git a/source/blender/makesrna/intern/rna_particle.c b/source/blender/makesrna/intern/rna_particle.c
index 07702f3b4b6..02105c7b425 100644
--- a/source/blender/makesrna/intern/rna_particle.c
+++ b/source/blender/makesrna/intern/rna_particle.c
@@ -471,7 +471,7 @@ static void rna_ParticleSystem_co_hair(
   if (step >= 0 && step <= max_k) {
     copy_v3_v3(n_co, (cache + step)->co);
     mul_m4_v3(particlesystem->imat, n_co);
-    mul_m4_v3(object->obmat, n_co);
+    mul_m4_v3(object->object_to_world, n_co);
   }
 }