3D projections?

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Old 01 January 2009   #1
3D projections?

Hi guys

I'm wondering about how to distinguish between camera projection mapping vs. regular texturing of 3D objects. I have quite a few techniques down as to how to project maps onto cards etc, but a few shots still have me wondering as to how they're done.

Have a look at: http://www.dylancolestudio.com/Demo_Reel/Reel640.html
Two shots: The beginning shot of the icy landscapes + The pan of the city skyline at 02:36. Is this projection mapping? I think not. Is it simple texturemapping in 3D? Or is there an "in-between-technique" that I havent learned about?

I'm also wondering about some of Chris Stoski's teckniques:
http://home.comcast.net/~chrisstoski/starwars_01.html#

Generating a 3D ambient occlusion pass as a basis for painting sounds great as far as getting an accurate lighting representation. But: what is the exact procedure?

Hope to get some info as to what I'm missing in understanding this workflow...

Thanks in advance,
Mike
 
Old 01 January 2009   #2
Camera mapping is done using a camera, preferablly set-up where you have the best view of a shot, and the textures are projected to 3d geometry or cards. Basically thats the concept.

On harder shots like you have shown in the links, an artist will create patches that will cover up "holes" or stretching in the texture as the animated camera moves. This is by using another projection camera that will produce the designated texture/paint. Your scene might contain more than 1 camera, it might be as many as 70 if needed. Oh and these projection cams are NOT animated just static ones duplicated from the animated camera.

The advantage of camera mapping aka Mattepainting over conventional 3D setup is that it renders quite fast since all your textures will have lighting effects built on them. The geometry is also not that dense, its more of a cheat actually.

Whereas textured objects needs to be lit and tweaked.

Hope that helps ya.
__________________
::Eric Dima-ala::
Lead Environments
DD : Van
www.ericdmatte.com

Last edited by eyecon : 01 January 2009 at 10:21 AM. Reason: added text
 
Old 01 January 2009   #3
Thanks

Definetely helps, thanks a lot.

Still wondering about painting on ambient occlusion passes though...any ideas on the exact procedure? (a great example would be the Chris Stoski Star Wars City scene)

In any case: Thanks a bundle
Mike :o)
 
Old 01 January 2009   #4
Depends on the program being used. In 3ds max you can use the MR renderer then throw a AO shader into the material override slot in the processing tab of the render settings. Though you need to tweak the AO settings depending on the scene and quality/time you're after.

New shader > diffuse > AO map (top of list)

Render settings > processing tab > enable then drag the shader from the material editor onto the material slot.

you could also bake the AO pass into all the geometry, but this can be time consuming.

Though in situations like the starwars shot, the whole scene has already been setup with shaders, lighting etc ... so still need to do the ground work first, the post projection is purely to speed up render time at the end. Unlike the DC superman shots which is probably photography patched together then projected if i remember correctly.

Dave.
 
Old 01 January 2009   #5
Thanks

Dave...

Thanks again, I'll do some more leg-work with the info...

Kind regards,
Mike
 
Old 01 January 2009   #6
Eyecon - followup

Eyecon

Hope I can squeeze a few more comments from you.
First of all, I really like your reel, impressive stuff...

I'm quite familiar with basic techniques, projecting onto cards and geometry. I am, however a bit confused about using multiple projections to cover up holes or unwanted stretches. Is this a matter of creating an additional project-camera, and then blending between the two using material-masks? (I'm using 3dsmax).
Also, I noticed your excellent shot that dives into a city roof-top. Can you elaborate a bit on how to create 360 degree mattes and how to project them? Just a few tips...:o)

In any case: Thanks a lot.

Kind regards,
Mike
 
Old 01 January 2009   #7
MDCAT Hi again

I'm not really familiar with 3ds max and projections with 3dsmax. But from what I can remember is that a collegeu of mine used a "multi-layer" material where he projects his images on geometry. You can add up more texture using this material and can plug in alphas too.

The workflow in projecting images is :

1. Paint your Matte / BG
2. Bring it to 3D app and try to follow the perspective and by setting up your camera.
3. Project our images on cards (for far objects) and boxes in near objects.
4. Test the projections by animating your camera to the desired shot.
5. Identify problem areas
6. Duplicate camera on the "best" view to fix problem area
7. Render and bring to photoshop (note: your render must be the same pixel aspect and size as your painting for best results)
8. Paintover in Photoshop
9. Project again using the duplicated camera.
10. Sit back and enjoy.

Note: never ever move your projection cameras, hide them lock them do whatever you want just as long as you don't move them.

Same goes for a 360. Like the ones in my reel, I just cheated by projecting images and patching them up. Near objects I just modelled really fast and projected the textures in layers. That took about 20 to 30 projections.

Hope this helps.
__________________
::Eric Dima-ala::
Lead Environments
DD : Van
www.ericdmatte.com
 
Old 01 January 2009   #8
Thanks

Definetely helps - thanks a bundle, Eyecon...

Time for testing,- hope I can trouble you again later on.

Kindest regards,
Mike
 
Old 01 January 2009   #9
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