MUltiple camera projection: from one to another

[Medusa]

Hi to everyone,
I have to create a multiple camera projection for a shot that start from an aereal view and end inside a village. I'm wondering how to blend the texture from one camera to another. Is it correct to use a bezier with an alpha channel for blending the texture before a project3dnode and after that use a merge material node?
I have also another problem: how can I put a correct texture without it stretches on the lateral wall of the houses?
Sorry for my english and thanks to everyone will have the patient to help me, I'm pretty new in the 3d space of Nuke and I didn't find any tutorial with multiple camera projection.

[Invader777]

Yes I can say that it's true. (Although I always put a premult after the alpha... this may just be a habit of mine though)

also - that stretching is happening because of the projection from the camera. To avoid it, you'll have to project from a more front on perspective to the surface of the object you are projecting onto.

Hope I've helped

[Medusa]

Thank's a lot Invader777 for your reply, I'was thinking that no one will help me
So, I have to project from the same view of the render camera deleting the animation from time to time, or I have to project also from different angles, from examples from left and right?
I have also a problem to match the textures with the 3d. I export the 3d model in fbx format and render from 3d the image to project. But when I project from the camera in nuke, the image does not match exactly with the 3d, and I have to scale the image, but it's not pretty accurate. I dont' understand what's wrong. I acquire the date of the camera by exporting chan information with max to nuke.

[werki]

I sometimes had problems with the fbx format. You could try obj just to make sure

[Medusa]

Thank's werki, I've tried but if I have 3d shot with more object, for example cornfield and houses, with fbx file I can export in one passage and have all in Nuke whereas with obj I must export one object at a time and then have lot of geometry node where project my image, so it became very complex. Do you know a way to export a scene like that in only one obj? I've tried to group object but then I can't export them, maybe I can convert all in editable poly and attach them but in this way I lost my material and freedom in action.

[werki]

Check your obj export settings. It works for me. I can have multiple objects in an obj file and import that into nuke.

[Medusa]

I be able to export multiple object in one obj thank you! but I've the same problem, when I project the render 3d it was not accurate because too small and i have to scale it x 1.34. it's a normal procedure or I was wrong in some passage?

[Invader777]

have you checked your camera settings in Nuke. is the FOV the same as in Max? Also are you rendering out your image with a 1:1 pixel aspect ratio?
If your camera is in motion then you could periodically delete the animation and project a still.
Or alternatively, If you have more images from different angles to project, then that's good too. The stretching comes from projecting an image that isn't perpendicular to the surface it's being projected onto. The more resolution your image has, the less obvious this stretching will be. (To an extent)

can I ask what the purpose of the projection is for? I know It's a silly question, but it seems to my understanding that you are rendering a 3D scene in max, exporting the mesh out, then taking it and recombining them in Nuke.

[alkali]

Try Nuke 'em.

http://www.vfxtalk.com/forum/showpos...06&postcount=1

[jokerxel]

There's a great episode of fxguidetv, #70 that explains in detail about camera projections in nuke. Here is the info:

fxguidetv #070
Watch High Bandwidth Episode | Watch Low Bandwidth Episode

Nov 05, 2009 - Florian Gellinger, vfx supervisor at rise | fx Berlin, shows off the work they did in Nuke from previs thru finish for the film "This is Love".

http://www.fxguide.com/fxguidetv.html