[Sidefx-houdini-list] Forward Kinematics in Houdini

Edward Lam edward at sidefx.com
Mon May 3 11:09:03 EDT 2010


Pablo Giménez wrote:
> But I want to know how the *Look at* parameter in objects works. Seems that
> is saving the transform in the PreTranform of the object.

Not really. The Look At is computed into the _local_ transform of the 
object when it cooks. The Pre-Transform is a static transform that is 
just multiplied into the local transform. Some advanced information can 
be found in the HDK docs here: 
http://www.sidefx.com/docs/hdk10.0/hdk_opbasics_objtransformmodel.html

> Without the Look At the rotation handler appears properly aligned to the
> object origin, but when using a look at object this origin changes but the
> rotation handler, aligned to object, doesn´t look to be aligned, so I am
> guessing this transformation is happening in the PreTransform.

It depends on which "object origin" you're talking about. The "origin" 
of the object's local transform parameters will always be relative to 
the Pre-Transform. The "origin" of the Pre-Transform will be relative to 
  object's parent (aka input) world transform.

Regards,
-Edward



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