#IK rotation problem
3 messages in this thread
One of our artists asked me to post a query on his behalf…
He is trying to create a segmented wing for a bird-like critter which can be
used in the inverse kinematics package. He is creating alternate wing-surface
and dummy objects. All objects are linked parent->child. The dummy objects
are apparently rotated in such a way as to provide the local coordinate systems
in which to rotate on vertices aligned with the edge – that is, the vertice
representing the edge shared by the two objects adjacent the dummy.
In some cases this has worked, however sometimes objects fail to "see" their
proper rotation system and fail to rotate properly, i.e. along normal global
vertices.
Has anyone any idea as to what he might be missing or, alternately, is there
anyone he can call directly at AutoDesk or outside the company who has already
dealt with the inverse kinematics system in order to save his sanity? Thus far
the tech support folks don't seem to have spent time with the IK system.
Thanks!
Brian V. McGroarty
High Voltage Software
Brian,
If I understand you correctly, it appears that your problem lies in either the
definition of the joint parameters, placement of the pivot points, or the
alignment of wing objects' local axes. Have your artist carefully check the
pviot points and joint parmeters of all objects. Analyzing and adjusting the
local axes gets trickier.
Did your artist model the wings using a lot of vertex and element editing, or
by attaching objects? Use of these techniques can result in local axis
alignments that you may not expect. Turning on the Axis option in the Joint
Parameters or Interactive displays will help you to analyze the local axes for
each object.
If you decide that the local axes are misaligned you can use commands such as
Reset Xform or Object Attach to alter their orientation. Make sure that you
unlink the objects before perfoming these commands and then re-link them when
you are done.
Steven
>> The dummy objects are apparently rotated in such a way as to provide the
local coordinate systems in which to rotate on vertices aligned with the edge
Ensure that the objects' pivot points are properly located. The pivot is the
point about which objects _always_ rotate in the Keyframer.
>>In some cases this has worked, however sometimes objects fail to "see" their
proper rotation system and fail to rotate properly, i.e. along normal global
vertices.
All rotations in IK are in reaard to that object's (internal) local axis. The
bounding box shows you the general orientation and you can see the actual axes
orientation with the Object Pivot command. In addition, each objects slides
along the axis of its parent. The object's orientation in the world (global)
has no effect on its rotation.
Hope that helped,
– Phil