Cameradata*-1

[tanukivilla]

Hello Board,

I'm fairly new to Nuke and am having quite a difficult time trying to invert some camera data. I've imported a .chan script into my camera. My Camera then is attached to the axis node of a Transform Geo node which stems from a Card node containing my image plane. When I view my Scene in 3D, the image plane is "locked" to the Camera, its translation and rotation mimic the Camera's as I scrub through the view timeline. What I can't figure out is how to make the image plane translate and rotate INVERSELY or opposite to the Camera. I've tried entering some expressions in both the Camera and Transform Geo nodes but my knowledge of this sort of thing is still at a very early stage. Any help/suggestions are greatly appreciated.

Best Regards,
Kevin

[user_deleted]

if you want to litteraly inverse the camera's transformation you need to make sure that the xform order is inversed, too, not just the knob values.
Why are you doing this anyway (I'm just curious)?

frank

[tanukivilla]

Thanks for the response.
Can I ask - where do I change the xform?
The result I'm after is to have a static plate, that image plane, translating and rotating in the render so it looks tracked into the shot. Currently, even though in the 3D view it appears locked to the camera, in the render the image plane is of course motionless. It's for a skydiving shot, the image plane is the ground, so it's back a bit in Z space, just want it to look tracked in. Maybe I'm going about it all wrong.
I'm really after this one solution but the bigger issue seems to be (besides the fact I'm new to Nuke ... that I'm not sure how you can still have the option to control some parameters in the image place - Camera relationship once you've imported a .chan file. In other words, how to still make independent motion/animation on a parameter or a couple different parameters once the .chan Camera file is imported and the Camera is linked into the Transform Geo axis without it throwing off the Camera's center point. Appologies if this sounds a bit convoluted.

Best Regards,
Kevin

[user_deleted]

Hi Kevin,

Can I ask - where do I change the xform?
it's in the first tab of the transformGeo node at the top. Not sure what exactly it's called, don't have Nuke aviailable to me at the moment.

So you want an image plane that acts as the camera's background like an image plane in a 3D in Maya or 3dsMax?
If so do the following:
-plug the camera into the axis input of the transformGeo node that moves your card
-set the Card's lens_in_focal and lens_in_haperture to the camera's focal length and horizontal aperture respectively
-set the translate.z of the TransfromGeo node to -1 and it's pivot to 1.

After that you can use the scale knob to set the card's distance to the camera (the card will always live in the camers's frustrum).
I made a gizmo for that but I haven't used it in ages and don't have access to Nuke at the moment so I can't verify if it still behaves as expected. If you want it let me know and I can email it to you (then again, maybe this is not what you're after at all and I got it all wrong).

As for your other question:
If you want to load a chan file but still need to edit the camera with a usable coordinate system (i.e. without screwing up it's center point), then load the the chan file into an axis node instead of the camera and use that as a parent to the camera (plug it into the top pipe of the camera node). make sure to use the correct focal length and aperture settings for your camera (you can inport the chan file for the camera as well to get it's values and then reset translation and rotation to 0).

After that you can use the camera's translation/rotation knobs to apply additional animation.

hope this helps.
cheers,
frank