Author Topic: Fake Hdr  (Read 2162 times)

2015-02-27, 15:02:58

Fiorentin

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Hello,

It is my first topic here but i've been following this forum for a while and have been trying out Corona for a couple of months now.

Im wondering if anyone knows of a good way to fake/build a hdr image from a regular photo in raw format. Or if theres any other way to simulate the light/color conditions when compositing a 3d object in a 2d still. Im a photographer and i want to put some 3d elements into my images. I will get a fisheye lens so that i can take som hdr panoramas in the future but i would love to be able to work with some images in my old catalog.

Any tips or hints would be much appreciated!

Thanks

2015-02-27, 17:20:08
Reply #1

Juraj

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I had to read your post 5 times until I understood what you want.

You're asking on how to build spherical and .hdr file from regular flat] single .raw photography.

Short answer: No.

Long answer: You can 'sort of' of possible re-save your .raw photo into .exr/.hdr because it has some dynamic range, depending on your camera sensor (NikonD800/Sony 7a have quite a lot stops, others...not so much).
It would hardly provide lighting information until the photo portrayed very diffuse/overcast lighting, but it could provide reflection.
You could then possibly map your photo to cylinder to get semi-panoramic probe out of it.

There were few white papers on Siggraph and some semi-build prototypes of applications that can composite 3D into 2D regular (tonemapped) photography using some self-aware algorithm. I don't remember the name, but you might be able to find it.
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2015-02-27, 19:53:45
Reply #2

Fiorentin

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Ok, sorry for being unclear. The cg 3d world is pretty new to me, i've build all my models/scenography afk.

Anyway, I like the long answer better! I will try to find those papers + make some tests based on your solution/idea.


2015-02-27, 20:28:53
Reply #3

fco3d

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Hi, if you want to start building your own HDRI I would recommend to read the blog of Jay Weston http://www.hyperfocaldesign.com/blog/page/4/ IMO he create one of the best HDRI for CG that I know of.  He explain why you will need more stops  than you usually take for regular artist or photography HDRI.
There is a long explanation to what Juraj mentioned, you could use your RAW image to some what give color variance to your scene, definitely for reflections but really it won't give you the real lighting.
You could also do a search for Chrome ball HDR image creation, it is also very used when you don't have enough time or space to use a fish eye lens ;)

Best luck.

2015-02-28, 13:16:02
Reply #4

Fiorentin

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Thanks, yes i will certainly have to do some studying and training before shooting hdri for ibl on set! Regarding compositing 3d into photos that lack an .hdr - using RAW image to get some color variance and reflections is just what I'm after. I know it won't get close to using a .hdr but its a good start. Then photoshop will have to do the rest :).

I found an article by Jay Weston on cgarchitect http://www.cgarchitect.com/2013/12/effects-of-hdr-vs-mdr-on-image-based-lighting where he had some tricks on merging the sun from an hdri into an mdr. Worth trying!