Extract Rotation Problem

[Max_Steven]

Hello,

I searched the vollume and youtube to find out extract transform and rotation from animated objects

I was able to produce the same result with  the CG Forge tutorial (www.youtube.com/watch?v=iSiyGr8p0p4&t=326s)

But when I applied to my animated object in sop somehow the transform is ok but the rotation failed completely

Can anyone point out what I did wrong?

 

Thank you

 

Extract_Rotation_Help.hipnc

Edited August 31, 2023 by Max_Steven

[Jesper Rahlff]

the reason your rotation gets lost is because you pack it, after the transformation has been applied, Thus rendering the primitive intrinsics to just an ident matrix.

If you look at the Crag test geometry, although he is packed he still has the packed intrinsic transform matrix information:

 

Your geometry does not:

 

If you want it to work with your tube as well, just apply the transform node after you pack the geometry and it will work properly.

 

Edited August 31, 2023 by Jesper Rahlff

[Max_Steven]

Thank you for the reply

Now I get it but what if I have alembic geo from maya instead of crag/tube.

It wont have orient data either right, so the only way to do is point deform?

Do you think is there any way to extract transform from geo in that case?

[animatrix]

If you don't pack the geometry, Extract Transform SOP should extract the transform matrix properly.

[Max_Steven]

Hello,

Thank you for your reply

I can replicate what you said with Craig but when apply to the geo cache it's just not working

Maybe because the original cache is deformed mesh therefore it doesnt have the rotation data?

In this case what should I do? 

Sorry for my small brain

Extract_Rotation_Help2.hipnc

I couldnt upload the geo cache file so here is the google drive link

https://drive.google.com/file/d/17u6vEwdcUTw_HxJrhpAqyXPMuV253jwy/view?usp=sharing

Edited September 1, 2023 by Max_Steven

[animatrix]

That link is broken. It depends on the geometry. Extract Transform can only extract rigid transformation, not deformation, which will result in inaccuracies in the rigid motion estimation.

[Max_Steven]

Sorry I just updated the link
Oh I mean I dont need to extract all the points just centroid point to put a volume sim on to that part

For now the transform is ok but not the rotation which drove me crazy

[animatrix]

You can't derive a rotation matrix just from a single point without any other information.

If you want to align your sim to another object like thrusters, there are many ways like isolating a single central face and aligning the simulation using Extract Transform SOP to extract the transformation matrix. You just have to make sure there is a reference frame of the engine that's also aligned to world axes and at the origin so the simulation at the origin can be matched perfectly to the animated version. Post offsets can be applied after transform matching.

[Max_Steven]

OMG I just got a goosebumps :))

Why i didnt think about put the reference frame of the engine properly to world axes ;))
Thank you so much for the hint. Will jump into Houdini right awayyyyy

[Max_Steven]

Finally made it

I just have to define the orient for the geo cache

Thank you guys all for the suggestions 

 

Edited September 1, 2023 by Max_Steven