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View Full Version : HDRI compositing trick I must know!

Rusherific
10-07-2006, 09:58 PM
So I'm a lightwave guy, but I've seen some renders from what I think is Max, of the usual 3d car composited with a real photo background...Thing is lately I've seen backdrop images used that I know are common HDRI's! Of course I know its common to use HDRI's as lighting/reflection, but I don't understand how guys are taking these spherical/probe maps and using them as the actual composited background, if that makes sense. I know in the typical usage of HDRI's if you were to make it visible to the camera the perspective is distorted and terribly zoomed because of the spherical mapping around the scene, at least in lightwave. Is some company making HDRI's with regular camera shots in addition, or is there a trick to taking an HDRI probe/map, putting your objects "in" it, and using it as an actual background with a usable perspective? I have Dosch's super hi-res 6k maps, which have the resolution to be more than lighting sources, but again I don't know how you would use them as backdrops?? I hope I'm getting across what I mean. I really don't know how this is done!

Thanks,
Devin
Kai01W
10-07-2006, 10:53 PM
Are you sure these are just common HDRs? Otherwise, take out the silver ball, zoom out, push the button a few times...:)

-k
Rusherific
10-07-2006, 11:05 PM
Thanks, but I wouldn't be asking if I made my own :p
payton
10-08-2006, 10:31 AM
well, im new to this stuff too.
but when im using a spherical hdri for image based lighting in maya, its not distorted if primary visible. this distortion occurs here when using cubic maps.

my 2 cents ;)

payton
bartrobinson
10-09-2006, 04:32 PM
It SOUNDS like you may be a little confused as to what an HDR image is. To help clarify, and anyone feel free to add on and correct, HDR does not equal Spherical image made with reflective sphere. HDR means High Dynamic Range (extra light information) and is usually acquired with multiple exposures from a camera. It doesn't matter what the camera is pointed at. The spherical images are mainly used for lighting (diffuse, specular, reflections, ...) If someone is ACCURATELY compositing a CG car onto an HDR background, what you are seeing is likely just a plain shot of a background with HDR data to maintain fidelity in the background photo and perhaps allow flexibility and control of the background in the final composite. Probably a spherical version of the scene is being used for lighting in the 3D program. Hope this helps.
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