Imported Mesh And Camera Not Ligning Up?

[user_deleted]

Hey gang - (propably frank )

I rendered a 3d scene from maya and then exported the cam animation and part of the object. I've imported it all into nuke (see accompanied screenshot) and have been playing with it all night and can't get it. All trans/rot values match the maya scene exactly but the Nuke camera view doesn't quite line up with the render. The move is right but something is placed incorrectly because the object floats.

I've attached a super-small video where you can see the obj (black window trussing) floating against the maya render. Anyone have any experience with this issue?

screenshot
video

Thanks

[lebedev2]

Just from looking at your screen grab and not seeing your camera settings it looks like your filmgates don't match. In Nuke make sure that your Camera H and V aperture settings match Maya's filmback. Nuke's will be in mm and Maya is inches so you open up your camera's attributes in Maya and under filmback take the numbers from the Camera Aperture setting, convert them from inches to millimeters and place the numbers in the Nuke Camera's horiz. and vert aperture and I think that will do what you want.

s

[user_deleted]

yes, defintely check your film back.
another culprit that likes to get in the way is the camera's rotation order. I believe in your case it should be set to "zxy".

[user_deleted]

Ok guys, guess I'm gonna have to dive deeper into this. Here's my exact scenario:

In maya, the object that I'm exporting is not centered in the scene, so it does have some translational values. I'm exporting it as an obj, should it be at the origin with the translates zerod out? Export the chan file from the camera.

Nuke: Import the obj, into Scene>Object>objReader. Connect it to a scene with a new camera. In the camera dialog, import the chan file and enter the horiz and vert ap sizes after converting them from inches to mm. Grab a scanline render from the scene and merge that over the maya rendered plate. I've switched the rotation order and xyz seems to be the closest match.

I'm quite confused why they don't line up, what am I missing?

[user_deleted]

what render resolution/image aspect was your maya camera/scene set to?
if you don't connect an image (i.e. Solid) to the ScanlineRender node's background pipe to dictate it's output resolution you have to make sure that your script settings are set to the correct format/image aspect to ensure correct output resolution.
as far as I know an obj exporter should bake all translations so you shouldn't have to zero out your object in Maya. Having said that I have seem some really dodgy obj exporters so one can never be too sure without checking. Then again you'd see if the object is located in the origin in Nuke or if it's offset.

so to summarize:
-make sure that the Nuke camera has the same filmback as your Maya camera
-either use a solid node as a background for the Render node or use the script settings to set the Render node's output resolution if no bg is connected to it. This resolution should have the same aspect as your filmback (h-aperture/v-aperture = image width/image height)
-rotation order needs to be correct, usually 'zxy' but depending on workflows and export scripts this may be different.

If all this is correct then maybe you're using animation controls in Maya that aren't picked up by the chan exporter?

cheers,
frank

[user_deleted]

OK - here's what went down. I was sure that everything matched the maya camera exactly and it did. I made sure my scenes resolution was correct in nuke and still it didn't work. My Nuke camera's film back was properly converted (my .chan exporter coverts to mm and tells you in the feedback bar of maya), but here's the catch - I never set the film back! Since there was no live action tracked in this shot I didn't even think to set it. For those of you working with a similar problem - in the shape node of your maya camera, scroll to Display Options and tick 'Display Film Gate' and 'Display Resolution Gate'. Trying to do it from the viewport only lets you toggle between the two. But, doing it in the AE, you can have them both on at the same time. THEY SHOULD MATCH!! If they don't, welcome to nothing ever lining up.

Thank you Frank & Sloth, it took a bit, but I found it!

~Scott

[maya-man]

Thanks, this is a valuable thread as I just tried re-doing some Maya cam projections in Nuke and I think I had a similar problem, ie. the projections were slightly off. I'm pretty sure the problem is covered by something mentioned in this thread so I'm filing it into my "alternative nuke docs" text file.

Cheers,

Michael