Problems with scaling CVEX volume cloud system

[Erin]

Hi everyone,

I have a problem that I don't really understand.

I have followed the CMIVFX tutorial to create a volume cloud system with CVEX at rendertime, but now have to add the system to an already existing scene. Everytime I scale down the Geo containing the cloud system, I loose all detail in the render. So I thought alright, I'm going to scale up the scene with my tracked camera instead, but everytime I do that, I get the same problem. I'm assuming this has to do with the CVEX and that there is a solution for this that I am missing. I have tried playing with the volume step size in the Mantra node, but had no success. I'm very very new to this and it is quite confusing, so I'd really appreciate some help.

This is what it should look like:

This is what it looks like after scaling up the scene with camera:

Edited May 1, 2012 by Erin

[Erin]

Just found a solution for this.

Didn't know that Volume Step Size is apparently calculated in camera and not world space, so if the camera gets scaled up or the volume scaled down, then you get a very different result.

Found this post by Serg

What I have done in the past to remove the scaling, is to create a new camera with it's view and rotation parms linked to the scaled camera, and use a "origin" expression to link the transform to the scaled camera's world position.

Since I had scaled the cam up myself, I just did that and then multiplied the transform values by how much I scaled the original camera, instead of using the expression.