Help on Perspective Projections

[alexx]

you mean camera projections?
whats the deal about them?

alexx

[Jhonus]

I'm talking about when you create a projection node and in its attributes you change it to Perspective (rather than planar). It basically lets the projection node match a camera of yoru choice.

Then what i want to do is project the photo onto simple geometry and animate the focal length of the camera.

[alexx]

the focal length of whic camera? the one that is projecting?

[Jhonus]

thats right........ although technically the projection node is doing the projecting.

[alexx]

sorry.. deleted the old post, since after posting i read that you already mentioned the idea of mapping to a easy surface..
so which camera?

[Jhonus]

ok.

the camera that i render from...... the one that is trying to match the photo.

[alexx]

if you change the focal length of the projecting cam according the change to the render cam.. it could work (wrom what my humble brain is able to think about right now) :)

[Jhonus]

i know it can work....... i've seen it done on an advert which they used max for.

i'm just wondering how the heng you accurately match the perspective and relative scales of objects from a photo in 3D.... it has to be spot on for it to work seamlessly.

[alexx]

if you wanna do that baking the texures might help after projecting them..

[tomb]

I heard a talk from one of the ILM matte painters and he explained how he uses this technique.

First you create fairly simple geometry and light and render your scene. Take this render into Photoshop and do all your matte painting directly over the top of the render. Save it from Photoshop and project the image from the same camera you rendered from. Turn off all the lights and turn on ambient lighting.
You can get away with this if the camera isn't moving in the scene too much.

I was suprised by the software the matte painters were using on Attack of the Clones: Photoshop 3, Electric Image & Cinema 4D. It just goes to show it's all down to the artist not the tool (although I don't know how I would live without more than one Undo in PS).

[playmesumch00ns]

Did the same thing in that awesome aerial shot of Stalingrad in Enemy at the Gates. Looked beautiful

as for your problem krugar...theoretically if you take accurate measurements of everything in the real-life scene, and note down your camera settings (focal length, zoom etc), then recreate these exactly in Maya, it should look the same. I say should, but it probably won't be exact. I guess it's just a case of trial and error

[alexx]

the method i saw was a bit different but with the same result (done by eric chauvin, who worked on contact and star wars 3-6 redo afaik and much more: http://www.blackpoolstudios.com/)
btw.. he worked with electric image as well.. hell fast rendering :)

you take your photo and draw in some perspective helper lines in photoshop. then you take that image and put it as an image plane in maya.
now you build your objects that you want to be mapped and move them to the desired positions (and alter them there to match the rough topology of the image)
when you have that done you can either go rendering with slight cam movement or if there are occlusions that mess up your image (like a collumn that moves so much that you can see the collumn texture behind it on the wall again) you need to go back to photoshop and retouch your images:
e.g.: you need to make 2 maps.. one unaltered: the map that gets projected on the collumn and another one for the background in which you painted the collumn out (at least as much not to be visible in the animation anymore).

painting the texture directly over the geometry like proposed by tomb may sometimes be faster.. but you might not need to do all that work since sometimes it will work without.

a last word:
of course you can not move the projecting cam later.. you need a new one for the animation - but i think you know that :)

cheers

alexx

[CGTalk Moderation]

This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.