issues with scaled camera and volumes

[Whatsinaname]

In a scene, there is a camera coming from Maya that was exported as an Alembic. In order to make things work efficiently in Houdini, I had to scale down the camera by 0.001, using a Null SOP on /obj level.

 

The problem is, this camera does strange things when rendering volumes, it seems like it cannot correctly interpret some information, anymore:

 

 

When I create a normal camera that is not scaled, it works fine:

 

 

I also created a camera in Houdini and parented it under the cam in question, but it doesn't inherit the ABCcamera's movement. When I uncheck Keep Position on Parenting, the same weird rendering comes out of my standard Houdini Camera.

 

Does anybody have an idea how I could possibly turn that camera from Alembic into a standard Houdini camera, or of I could attach a Houdini camera to it without scaling anything...or how to avoid that issue in general?

 

EDIT:

 

Ok, this thread was rather helpful:

 

http://forums.odforce.net/topic/20712-scene-transformations-and-rendering-volumes/

 

It seems like scaling is affecting the camera rays a lot, therefore my "weird" results are correct. It helped to use a multiplicator on density to have the overall scaling done correctly, again.

 

Anyways, this is a bit cumbersome (workflow-wise). Is there a good other workaround for the cameras, like recreating a Houdini camera that is not scaled from the (scaled) Maya/Alembic imported camera? How do you get along with those issues?

Edited October 21, 2014 by Phlok

[jkunz07]

I think on the camera node you can go to edit -> parameters

unhide the scale parameter

type in  1/origin("", ".", TX), 1/origin("", ".", TY), 1/origin("", ".", TZ)

In the respective components

 

That should invert any scaling the camera has, reverting it back to 1

[thornleyj]

Hi,

 

If you're scaling using a null object, place a blend object between the null and camera and in the "Mask 1" set of toggles, turn of sx sy sz. This will filter out the scaling part of the null transform being passed to the camera.

 

Hope that helps!

Joe

[XRM]

Hi Florian,

             This a common thing in Houdini Scaling camera and light can cause this thing. Use the below mention expressions to fix it

 

Unhide scale in camera and

origin(opinputpath(".",0), "", "SX")    for  x

origin(opinputpath(".",0), "", "SY")    for  y

origin(opinputpath(".",0), "", "SZ")    for  z

 

that should do it.

 

Cheers!

Edited October 26, 2014 by XRM