[Sidefx-houdini-list] clean transforms

Robert Kelly isstuff at gmail.com
Fri May 28 12:05:08 EDT 2010

Quite often I would add extra nulls in the hierarchy because it was
more predictable than cleaning transforms. If i had a bone that was
controlled by the animator i would most often have a fairly clean set
of rotations with maybe one angle set to a non zero value and that can
be saved as the default in the hda of the character. Although i was
making a rig that is made of limbs spines and hand HDA's much like the
SESI rig is now made. The per character customization was done in a
layer around those tools. The idea of separating the deformation rig
from the animation rig was one i had to steal from the sesi rig, that
is just plane smart!

I found my self extracting transforms on bones that i create through
the interface most often so i could take control of those values only
cleaning them after I had set them to something like t=0,0,0

A side note on rigging in houdini the blend object is about all you
need to do most of your rigging. you can make it do a look at
constraint when you put in 3 inputs and tick orient axis. the first
input is the origin of the lookat and you should have all the
translation come from that source, unless you know what your doing,
the  second is the lookat target, and the third is the up target

I had an idea years ago to make a rig that calculated its values in
vex. Now my vex skills are up to the task i don't know if it is that
good of a fit. But houdini's rigs don't run that fast when you get 5
of them in a scene. It wouldn't hurt to get curve interpolated
Quaternary rotations too, who wouldn't want to forget all about gimble

On 28 May 2010 08:26, Alex Lim <list at poh-yee.com> wrote:
> Hi,
> Other people might have a different opinion on this, but IMHO, yes and no.
> Yes, I think you may get into trouble if you zero'd an Object out
> somewhere in the world space, but then later you perform additional
> transform operation there, you may not notice (initially) that there are
> cleaned transform in that node. So if you or someone else do a lot of
> referencing to that Object chain, there is a little danger that when
> your hierarchy get complicated, you will be spending a lot of time
> figuring out why the numbers don't match up just because you used some
> expressions that may not take into account pre-transform.
> I rarely see pre-transform on FX and lighting setups. Mostly on rigging,
> it seems. Which made sense because you'd probably want to give animators
> a clean, zero'd parameter rig to work with.
> No, pre-transform can still be extracted regardless, either by
> combination of objpretransform() and explodematrix() or other expression
> functions. It is a useful thing.
> IMHO, you should be able to work without cleaning transform in Houdini
> tho. But if you have to, just make sure things are well labeled/noted
> and you should be okay. :)
> HTH,
> Alex
> On 5/28/2010 8:00 AM, James Rutherford wrote:
>> Probably a dumb question but will get into a future problem if I clean transforms on chain root nulls on a rig I'm working on.
>> Jim Rutherford
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