Thread: create hdri?
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Old 22-01-2006, 11:09 PM   #12
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Hehehe Gest, explosure, I like the typo

Yo Mc Fleyru

Using one of these values on a standard one, you'll have the LDR (low dynamic range) images you need, the exposures.

Or on your digital cam, you can have them (but not as much) ... the values are 100-200-400, usually, if i'm not wrong.

And here are the transformation process, summarized.

HDRShop allows you to create a high-dynamic range image from a sequence of standard 24-bit images taken at different shutter speeds. The images should be taken without moving the camera, and should be bracketed so that the darkest parts of the scene are clearly visible in the longest exposure and the brightest parts of the image are not "blasted out" to white in the shortest exposure. ...

Summary : You need a serie of pictures with a standard camera. Several exposure times. 8 is optimal, but i think 3 would be a good start. Don't think about playing with the contrasts and brightness in toshop, from a standalone photo, ... the result looses a lot and lighting will be pale. Here you can see the result , with one photo. Well, it shows clearly why hdri stores color values with a 32 bits floating precision, for each RGB (so the 96 bits compared to the original 24 bits image(s), 3*8 bits) .

So IF you got at least 3(8) photos with different exposures, than you can assembly the serie with hdrshop, here's how

After all that, you got some HDRI map you can use for lighting, but not a true environmental/reflectable panoramic HDRI. I mean a .hdr file you could map on a sphere without any distortion. Having such panorama, is one step up in the creation of real env. HDRI.

You'll often read about mirrored ball. And here's the technique that will provide best results.

So to your question MacFLeury "is there another way than with mirrored ball ?" ... yes, if you got several exposures, at least.

Hoping not leaving too much errors or typos :blush:

Last edited by Pyrus : 22-01-2006 at 11:15 PM.
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