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View Full Version : how to texture a city? camera projection mapping?


av23
07-23-2011, 01:20 PM
I was just wondering if you were going to create an aerial shot of a city that was going to be flooded by a tsunami. Would the practical thing to do be to get a high res pic of city and camera map the projection onto stand in geometry as opposed to actually modeling and texturing the entire city?

Also would you do the entire city from one projection or multiple camera projections?

MasonDoran
07-23-2011, 10:38 PM
Projections are entirely reliant on the camera movement. Once you start seeing holes in the projection, or it starts to stretch, you will then need to create a new projection for these areas.


Projection are kinda like cheats, they can only get you so far, before its no longer possible to use them. Most noticeably, the camera projection will only be useable from the same view as that of the source material.

SebKaine
07-24-2011, 09:29 AM
well for environment i will never unfold one single uv , and only rely on camera mapping. camera mapping is the best invention in CG :) and if i were you i'll give a try to nuke 3d environment, cause you'll go 5* time faster and most important you'll get an interactive feedack of your projection. of course this is a very subjective point of view :), but if you need photorealism you will quickly see that the best way to get it is to project a photo ...

i give you a link to the demo of friend with lot of making of it can be helpful to understand extensive camap
http://vimeo.com/5742046

you need
- clean model
- nice occlusion + keylight direction
- you make your key projection in toshop
- you make your corrective projection

gnomon has wonderful video on the subject ... the best that you can find ...

av24
07-24-2011, 10:50 AM
thanks what is toshop?? do you mean photoshop? Also what software does he use for modelling? also are the white shots of the 3d buildings the ambient occlusion?

lastly would all of those france shot be generated from one matte painting or multiples? if multiples would you use lots of cameras projecting and then make texture reference objects and move them into place? or just one matte painting?

By corrective projection do you mean you do one key projection of one matte and see what you can get away with then add extra matte projections of individual elements in where it doesn't quite work?

SebKaine
07-24-2011, 11:38 AM
well i'm not an expert environment artist but you will have to use several tricks for this kind of shot , again gnomon will explain this far better than me but

the general rules is :
foreground element = detail modeling + projection
midle groud element = mid detail modeling + projection
background element = very low modeling or sprite + projection
this rules is needeed to maintain a realistic parallax and relief in your image

the idea is to create your layout matte in photoshop (toshop ...) you organise your image with
- foreground
- midleground
- background
you can divide each layer in sublayer
- foreground Left , Right , Center etc ....

to design your matte you can block the perspective and lighting with a raw modeling + occlusion ( the black and white pass you see in the video ) + keylight pass. occlusion will give a fake of the GI in your image the soft shadowing.

There is no rules for the organisation of your projection it depend on your shot , you need to be logic and make the choice by yourself.

the most important i think is to go step by step ,
- fisrt you make very raw concept and very raw modeling and you camap it and render the sequence.
you will see directly what works and where problem arise then
- you refine your concept,your modeling and your projection and make a second test ...
you repeat this again and again until every problem is solve ...
And in fact corrective projection is the fact that if your camera move , your main projection will not cover all the geometry , and you will start to see the texture stretching on some object so you will need to use secondary projection to solve this.

i give you a link to 3 diamond tutorials :

http://www.thegnomonworkshop.com/store/product/59/The-Techniques-of-Dylan-Cole-3

http://www.thegnomonworkshop.com/store/product/81/Camera-Projection-Techniques-in-Maya

http://www.thegnomonworkshop.com/store/product/710/Matte-Painting-for-Production-with-Jared-Simeth

cheers

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