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View Full Version : HDR lighting a cg car with moving cameras?


cooperunionstud
09-14-2010, 07:29 PM
what would be the best approach to integrate a moving cg car, with live footage that also moves? A HDR still would only work for certain angle and distance before it starts to break down in realism. If a car is moving on the street and the cameras are also following it, what would be the best approach to get the proper HDR image for reflections for such situations? Also since HDR images are normally taken with multiple exposures, are there devices out there off the shelf that can shoot HDR footage?

playmesumch00ns
09-15-2010, 09:59 AM
The best way to do this would be to rebuild the street environment as a low-res model and texture it using HDR photographs, then just directly raytrace that for accurate reflections.

There are devices that can shoot an HDR in a single capture, for instance the spheron camera.

cooperunionstud
09-15-2010, 10:14 AM
if one to were to take footage from a moving car with a attached locked camera, like this forexample

http://www.drivearabia.com/news/wp-content/uploads/2008/05/camera-stand-1.jpg

or this

http://brettacurtis.com/images/side_car_reflectiontiff123.jpg

and replace the car with a cg version, is there anyway to maintain a accurate reflection lighting to match the footage in the background? Would an HDR footage of chromeball shots be the only way it would work?

earlyworm
09-16-2010, 04:18 PM
On a recent film I worked on - the camera car had two motion picture cameras with fisheye lens mounted on the front and back of the car - in addition to the main camera shooting the background plates.

I took the two fisheye plates, unwrapped each in Shake (using an inhouse plugin) to a latlong image - blurring and blending the areas not photographed to fill in the gaps of the latlong. For one shot they only shot a fisheye out the back of the car - so I took the rear fisheye, reversed and offset the timing (so it looked like it was going forward) and then plugged the reverse/offset output into the front fisheyes node tree - one of those things you'd never be able to tell with everything flying by so fast.

Then outputted that as a latlong image sequence. Attached the latlong image sequence to my ambient and reflection lights then constrained those lights to the matchmove of the car (so everything was relative to the moving vehicle). I also reprojected the hero plate onto reflection cards (lowres geo will work as well) so the reflections would be spatially correct (well... approximately correct).

Looked fantastic.

No HDR needed - the film scans worked fine on their own with just a single exposure.

cooperunionstud
09-16-2010, 10:16 PM
thanks for the recommandation.
i will try that out!

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