[Robotics] Python control of armature in the GE

Mon Sep 14 21:58:57 CEST 2009

You can read armatures (all poseChannel and bone fields that matters in
the GE) and you can write pose channels (only position/orientation
though).
The detailed documentation on this API in the BPY_GE directory that you
will find in the builds. Open the index.html in your browser and select
the BL_ArmatureObject, BL_ArmatureChannel, BL_ArmatureBone classes on
the left panel: you will find all the properties that you can read or
write in the GE.

Here is an example on how you can get access to the pose channels in a
Python controller in the GE:

cont = GameLogic.getCurrentController()
# get reference to armature object
arm = cont.owner 
# list of pose channels for all bones
channels = arm.channels
# access by bone name    
pose=channels['Bone']  
# read current joint rotation
print (pose.joint_rotation)
# set joint rotation for next frame
pose.joint_rotation = [0.0, 0.0, 0.1]
# you can also set euler angle
# pose.euler_rotation = [x,y,z]
# you can get rest pose information from the bone
bone = pose.bone
# all properties are read-only
print (bone.bone.mat)
# make sure the pose gets updated on next graphic frame
arm.update()

The above code shows the path of references:
GameLogic.getCurrentController().owner.channels["<bone_name>"].<pose
properties>
GameLogic.getCurrentController().owner.channels["<bone_name>"].bone.<bon
e properties>

There is also a path for constraints:
GameLogic.getCurrentController().owner.constraints["<bone_name>:<constra
int_name>"].<constraint properties>

Thanks for confirming that the build works on a recent Ubuntu distro, I
have upgrade mine for a long time.

/benoit

-----Original Message-----
From: robotics-bounces at blender.org [mailto:robotics-bounces at blender.org]
On Behalf Of Florian Lier
Sent: lundi 14 septembre 2009 18:18
To: Blender and Robotics
Subject: Re: [Robotics] Python control of armature in the GE

Hey all,

for claryfication ... I can read write armatures in the GE now?!
This is what I understood from the last mails :)

My goal is to write a time triggered script which manipulates the
armature.

Benoit - if so, can you provide us with some sample code?

BTW: You build works fine on Ubuntu (32Bit) ) 9.04

Cheers, Florian

Benoit Bolsee wrote: 

Blender 2.5 needs Python 3.1 indeed (at least the GE). 

Regarding Blender module, yes it's gone, you need to switch to the new

RNA and operator API.

You have the documentation (still partial) here :

 http://www.graphicall.org/ftp/ideasman42/html/bpy-module.html

The principle is that you get reference to the data block you want to

manipulate from the context

(http://www.graphicall.org/ftp/ideasman42/html/bpy.types.Context-class.h

tml): you start from the main and dig through it.

Afaik it's not available in the GE yet.

So in the GE you must stick with GE API only, which hasn't changed.

You will noticed that I implemented proxy classes in the GE to bone,

pose channel, and armatures. So you don't need bpy for that.

I hope this news are not too disappointing ;-)

Regards,

Benoit

-----Original Message-----

From: robotics-bounces at blender.org 

[mailto:robotics-bounces at blender.org] On Behalf Of Markus Mehrwald

Sent: vendredi 11 septembre 2009 16:04

To: Blender and Robotics

Subject: Re: [Robotics] Python control of armature in the GE

Hi Benoit,

I figured out some other problems now. I got Blender to compile only 

with Pyhton 3.1 but now I cannot use my scripts anymore with 

the error:

Traceback (most recent call last):

   File "Steuerung.py", line 4, in <module>

ImportError: No module named Blender

Do you know what this could be or is there already a 

documentation for 2.5?

Thanks,

Markus

Benoit Bolsee schrieb:

I fixed CMake in the itasc branch. Sorry for the delay.

/benoit

-----Original Message-----

From: robotics-bounces at blender.org

[mailto:robotics-bounces at blender.org] On Behalf Of Markus Mehrwald

Sent: vendredi 11 septembre 2009 11:21

To: Blender and Robotics

Subject: Re: [Robotics] Python control of armature in the GE

Hi,

I just managed it to compile the branch with the ikplugin. For some

reasons I was not able to compile because of a few errors. I 

think its 

just some little changes in the CMake files. First of all the 

BIK_api.h 

was not found. I did it quick and dirty by copying the full 

path in the 

files where it is needed. The second thing was that obviously 

the libs 

bf_ikplugin and bf_ITASC are not in the list of libs to link 

against. Maybe you did not update the CMakeList or was it a 

problem of my computer?

Regards,

Markus

Benoit Bolsee schrieb:

Hi,

I have added support for controlling armatures through

Python in the

GE.

This is provided through the new proxy class

BL_ArmatureChannel that

corresponds to the pose channel structure. Most attributes match

directly the Blender bPoseChannel structure but I added a 

'joint_rotation' attribute that gives direct access to 

joint angles. You

can use this attribute to set the joint angles from

external data or

your own calculation and the armature will move according

to it. If the

armature is controlled by IK, you can read the joint angles

computed by

the algorithm. Full details is provided in the BPY documentation

included in the packages below. Download them if you want 

to know more

about it.

Other fix in this build is correct matrix operation with 

MathUtils:

http://lists.blender.org/pipermail/bf-blender-cvs/2009-Septemb

er/022245.html

For those who want to experiment, I made two builds on graphicall:

Linux:

http://graphicall.org/builds/builds/showbuild.>

php?action=show&id=1082

<http://graphicall.org/builds/builds/showbuild.php?action=show

&id=1082>

Windows:

http://graphicall.org/builds/builds/showbuild.>

php?action=show&id=1080 

 <http://graphicall.org/builds/builds/showbuild>
<http://graphicall.org/builds/builds/showbuild>

.php?action=show&id=1080

If your system is not in this list, you can check out the itasc 

branch and compile. For those interested in the 

implementation, look 

at the BL_ArmatureChannel.cpp module in 

source/gameengine/converter. 

If

you

have some ideas to extend the API, you are welcome to make your own

additions and send me the diff, I will review and commit 

them to SVN.

The itasc branch will be merged with 2.5 in the coming 

days, it would

be

nice to get some feedback before I start the merge.

/benoit.

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