Is there a command for getting world-space matrix of pose bones, same as obj.matrix_world
for objects? I found pose_bone.matrix
, but it gives weird result for me.
3 Answers
Yes:
As the documentation says, a pose bones matrix is in object space, this means - unless the object has no loc/scale/rot applied, you will have to apply the objects matrix.
matrix_final =
obj.matrix_world
@
pose_bone.matrix
This test script adds an empty at the pose-bone.
# Assume we are in pose mode with an active bone
import bpy
from bpy import context
pose_bone = context.active_pose_bone
# we can get the object from the pose bone
obj = pose_bone.id_data
matrix_final = obj.matrix_world @ pose_bone.matrix
# now we can view the matrix by applying it to an object
obj_empty = bpy.data.objects.new("Test", None)
context.collection.objects.link(obj_empty)
obj_empty.matrix_world = matrix_final
mathutils
now uses the PEP 465 binary operator for multiplying matrices.
matrix_final = obj.matrix_world * pose_bone.matrix
becomes
matrix_final = obj.matrix_world @ pose_bone.matrix
Since 2.8 object are now stored in Collections, so :
context.scene.objects.link(obj_empty)
becomes
bpy.data.collections['Collection'].objects.link(obj_empty)
Here is the complete script updated:
# Assume we are in pose mode with an active bone,
# and a collection named collecion exist
import bpy
from bpy import context
pose_bone = context.active_pose_bone
# we can get the object from the pose bone
obj = pose_bone.id_data
matrix_final = obj.matrix_world @ pose_bone.matrix
# now we can view the matrix by applying it to an object
obj_empty = bpy.data.objects.new("Test", None)
bpy.data.collections['Collection'].objects.link(obj_empty)
obj_empty.matrix_world = matrix_final
-
$\begingroup$ Thanks, this is useful ! But now I would like to ask, I have global_matrix, how to convert it to localtransform (localtion / rotation / scale)? $\endgroup$ Mar 13, 2020 at 16:00
Again with tip to tail offset.
Slight addition to @ideasman42's answer to enable globally locating to tip or tail of bone based on an offset. 0 is as above at fat end of bone (head), 1 at skinny end (tail).
This is to emulate somewhat the option in copy transform constraints to locate with offset along bone.
The vector
(pb.head - pb.tail)
describes the object space vector from head to tail A translation matrix is created to translate point of interest locally along the bone.
# Assume we are in pose mode with an active bone
import bpy
from bpy import context
from mathutils import Matrix
# add empty half way along bone
offset = 0.5 # 0 for tail 1 for tip.
pb = context.active_pose_bone
T = Matrix.Translation(
offset * (pb.tail - pb.head)
)
# we can get the object from the pose bone
obj = pb.id_data
matrix_final = obj.matrix_world @ (T @ pb.matrix)
# now we can view the matrix by applying it to an object
obj_empty = bpy.data.objects.new("Test", None)
context.collection.objects.link(obj_empty)
obj_empty.matrix_world = matrix_final