View Full Version : chrome balls and reflection maps
11 November 2002, 08:04 PM
I'm trying to do the live action cg thingy since i have access to a camera and a beta.I havent cooked up a story board or any thing yettt but since i'm going to need reflection maps of the scene i'd appreciate a few tips.
heres what i think i will need please let me know what u dudes think.(software:afx,combustion,max,maya)
1)markers for tracking(white scotch tape etc)...any tips ;)
2)chrome ball...is there a standard.What can i use as a last resort.Also how would I/camera man avoid being captured.If i shoot at diffrent exposures what should they be.Do i have to get all sides of the ball shot.
5)What can i use to query the quality of light...styro foam balls ??? any thing else and why ???
6)should i shoot a grid first to match the lensing and distortion of the lense.
i'm most shaky on the chrome ball part cause i dont think i will be able to get one...apart from getting it to work right.So any help from u guys will go a long way tahnx for listening.
11 November 2002, 11:46 PM
1. Track markers:
You don't need these, if you use an automatic tracking software like e.g. Boujou.
2. Chrome Ball.
These are called 'Reflective Spheres' or 'Iridiscent Spheres'. They are best bought in garden supplies shops (at least here in Europe). They are used for decoartive purposes in the garden. This btw. goes back to an old rite from Venice in the 13. or 14. century -- they should keep evil spirits away from the garden. Here are some links:
You shoot your chrome ball with a regular digital (still) camera usually fixed at eight stops (f8) but with different exposure times. See e.g. http://www.cgtechniques.com/lightbox/tutorials/fisheyepano/index.php 10-16 pictures should do. Write the exposure time down for each picture! You later assemble these pictures into what is referred to as an high dynamic range (HDR) image using the fine HDRShop program available for free here - http://www.debevec.org/HDRShop/.
3. Now for the problem with the photographer being depictured on the sphere look at this http://www.cgtechniques.com/lightbox/tutorials/getridoff/.
4. You don't need any styrofoam ball anymore if you successfully assembled your HDR image!
Instead, use the 'Specular Convolution' filter in HDR Shop to obtain the diffuse part of your scene's refelection in the chrome ball.
Finally you can use the HDR image(s) to light your 3d objects to seamlessly integrate them with the environment.
5. Why not. Depends on the FOV you use. It certainly gives you an advance, should problems show up in comp.
11 November 2002, 07:04 PM
thanks tre bien ;) .
about the markers...i'll have to go that way since boujou is like...10,000 $'s.
again thanx for the linx...and just one more favour.
i'm taking a video game mathematics course online and since ure technically hip...could i ask u a few questions when i'm stuck.(which seams to happen more often than i'd like ;) )...the math should be very elementary for you but i'd appreciate your insight and point of view.(wont bug you too much though).
11 November 2002, 11:42 AM
If you need excellent free tracking (only for non-commercial projects though, but very close to boujou), got to http://aig.cs.man.ac.uk/icarus/.
Btw.: to use this commercially, a license is only 1.000 US$.
And you surely you are welcome to ask questions. Preferrably via this frorum.
11 November 2002, 05:36 PM
icarus might be just the tool i need...apart from my own ;).
great.If i can i'll return the favour.So just ask.
01 January 2006, 11:00 PM
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