Automatic Maya to Houdini Camera conversion

#1 · 26. February 2019, 16:47

Hi,

I just realized that the camera in Maya is different in Houdini when exported as alembic with the prism shotcam export. I found the following in the houdini alembic docs, which explains the problem:

Working with Maya cameras

The Maya camera model works using two "gates": the film gate and the resolution gate. The film gate is what the camera can see, and the resolution gate is what is rendered.

The Maya camera has a lens squeeze attribute that has no equivalent in Houdini. To account for it and make sure the Houdini camera matches the Maya film gate, the following equations must be true:

a = 10h * l

p = (h * l * resy) / (v * resx)

There are more about the topic here: http://www.sidefx.com/docs/houdini/io/alembic.html

Would be great if there was a checkbox or something in the camera import state where you tell prism that it is coming from maya (or maybe it could know automatically somehow...?) and that prism would apply the math magic to make it match the maya resolution gate instead of the film gate.

#2 · 26. February 2019, 21:34

Does your alembic camera conversion tool, which you mentioned, take that already into consideration?

#3 · 26. February 2019, 21:57

Nope unfortunately not :/

#4 · 26. February 2019, 22:18

It should be possible to find out if the camera comes from Maya (at least when it was exported with Prism).

I added this as a note to [0013]

#5 · 28. February 2019, 14:34

Hi Richard, just a little update as I'm investigating the issue. It seems like to camera is matching fine in some shots and some not, so sidefx might have fixed the issue without updating the docs. Still not sure why some shots are not matching, but I'll keep you posted.

EDIT: nah.. it's not matching, my eyes got tricked.