Blender Foundation: Blender 2.x BF release: Detail: 24672 Bone.evaluate

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[#24672] Bone.evaluate_envelope() is misleading

Date:
2010-11-12 00:35 Priority:
3

State:
Closed

Submitted by:
Tom Edwards (artfunkel) Assigned to:
Campbell Barton (campbellbarton)

Category:
Python Status:
Fixed / Closed

Relates to: Duplicates:

Patches:

Summary:
Bone.evaluate_envelope() is misleading

Detailed description

evaluate_envelope() is available from Bone and PoseBone. However, it is only useful when used in conjunction with PoseBone.

Here is the process needed to check a bone's envelope strength for a vertex:

bone.evaluate_envelope( mesh.matrix_world * armature.matrix_world.copy().invert() * bone.matrix_local * vertex.co )

The problem is at bone.matrix_local. Regular Bone bones point down the Z axis, but PoseBones point down the Y axis (I assume there is a reason for this). The Y axis pose matrix is the one Blender uses to calculate envelopes, leaving the Z axis equivalent totally useless.

We can't stop people from plugging the Bone matrix into the function, but removing the function from Bone would send a pretty strong hint that PoseBone is the place to go.

Followup

Message

Date: 2010-11-17 03:37
Sender: Dan Eicher
Needs to be using bone->arm_[head,tail] because that's in armature (or parent, who knows?) space while bone->head is in bone local space.

Tested with (where Bone.000 has a parent);
C.active_pose_bone.evaluate_envelope(C.scene.cursor_location)
bpy.data.armatures["Armature"].bones["Bone.000"].evaluate_envelope(C.scene.cursor_location)

and they both return the same value with the patch but not without.

Index: source/blender/makesrna/intern/rna_armature_api.c
===================================================================
--- source/blender/makesrna/intern/rna_armature_api.c (revision 33110)
+++ source/blender/makesrna/intern/rna_armature_api.c (working copy)
@@ -51,7 +51,7 @@
float rna_Bone_do_envelope(Bone *bone, float *vec)
{
float scale = (bone->flag & BONE_MULT_VG_ENV) == BONE_MULT_VG_ENV ? bone->weight : 1.0f;
- return distfactor_to_bone(vec, bone->head, bone->tail, bone->rad_head * scale, bone->rad_tail * scale, bone->dist * scale);
+ return distfactor_to_bone(vec, bone->arm_head, bone->arm_tail, bone->rad_head * scale, bone->rad_tail * scale, bone->dist * scale);
}

#else

Date: 2010-11-17 04:27
Sender: Campbell Barton
applied r33118.
closing.

Attached Files:

No Files Currently Attached

Changes:

Field	Old Value	Date	By

Resolution	None	2010-11-17 04:27	campbellbarton
close_date	2010-11-17 04:27	2010-11-17 04:27	campbellbarton
status_id	Open	2010-11-17 04:27	campbellbarton
assigned_to	none	2010-11-12 07:32	aligorith