Realistic exterior/interior HDRI lightng?

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  04 April 2010
Realistic exterior/interior HDRI lightng?

Hey guys

Im looking for a good tutorial on exterior/interior HDRI lighting. I can use the Sun sky system but i want to broaden my lighting knowledge and add that individual touch to my scenes.

Appreciate any links you guys might have.

thnx
 
  04 April 2010
Most people use the sun sky system because it produces realistic light if you use it in conjunction with the camera lenses and a linear workflow. If you're using mental ray, these are good:

http://www.floze.org/2008/07/six-tu...ade-part-i.html

HDRI lights aren't better - they are just easier to use if you need to match an environment. Using the sun sky system is a lot harder because it often involves a degamma/linear workflow.
 
  04 April 2010
HDRI Lighting

I donīt like to accept that computer generated sky systems should be the better choice compared to real world scenes photographed as HDRI.

Does it make sense to compare these two methods at all?

One is completely artificial Lighting and it will produce very smooth but well, somehow artificial situations. Perfectly e.g. for stuff which needs neutral, smooth backgrounds but somehow lifeless.

The other side, photographed HDRI panoramas are a totally different approach in my eyes. Here you will get lifelike, often clearly defind Ligthing situations whith a high taste of realism.

Of course it is more work and also maybe harder to get the correct lighting using an HDRI because you have to choose the right one, use it at the correct exposure/rotation etc. but hey, this is part of the magic going on when producing artwork.

Have a look at this panorama I did a few weeks ago with the new EOS 7D. I donīt think that you can capture such a situation (reflection/lighting) with a generic sky-system:



If you arenīt convinced, give the full resolution picture a try:

http://www.sachform.de/free_downloa..._Final_Logo.jpg

Cheers,

Jan Häusle
Sachform Technology
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  04 April 2010
Originally Posted by jhaeusle: I donīt like to accept that computer generated sky systems should be the better choice compared to real world scenes photographed as HDRI.

Does it make sense to compare these two methods at all?

One is completely artificial Lighting and it will produce very smooth but well, somehow artificial situations. Perfectly e.g. for stuff which needs neutral, smooth backgrounds but somehow lifeless.

The other side, photographed HDRI panoramas are a totally different approach in my eyes. Here you will get lifelike, often clearly defind Ligthing situations whith a high taste of realism.

Of course it is more work and also maybe harder to get the correct lighting using an HDRI because you have to choose the right one, use it at the correct exposure/rotation etc. but hey, this is part of the magic going on when producing artwork.


The sky system that most 3D apps these days use is based on a paper published which presents a pretty good approximation of a cloudless sky, based on real-world measurements, that can be controlled by a few parameters:
http://www.cs.utah.edu/~shirley/papers/sunsky/

The main advantage is obviously that you can change the sun position and color as you see fit, and memory usage is kept to a minimum since the whole thing is procedural.
The biggest disadvantage of course is that you lack clouds.

Don't get me wrong, HDRIs are great, but there are certain situations where it's better to skip the whole IBL thing and go for the sun/sky system, and seeing lots of great images produced with it, I wouldn't go as far as to write the results off as "lifeless" (the same thing can be said for many HDRI-lit images as well, it depends entirely on the artist).
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  04 April 2010
Hi Niko,

you are right, of course it depends on the artist. And of course for some situations this may be the best solution (clean, smooth situations as I wrote). But hey, that never was the point where HDRIs came into account.

"The biggest disadvantage of course is that you lack clouds." <-- And that such Images tend to have some kind of similar look (of course you can influence this with various tricks).

If you want to get a studio or clean outdoor atmosphere without a detailed reflection environment, then use a studio or physical skies, no problem.
But if you want your model to stand right within the nature, city, street, etc., getting not only a realistic lighting or just need it to capture agile reflections then I would go for HDRIs.

So I would say, there is no competition between these two techniques, you just have to choose the right one for the task. I just donīt find it usefull to directly compare the two techniques on a qualitative basis.

Cheers,

Jan
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  04 April 2010
When using phsyical sun & sky, you can use an mip_rayswitch shader, which can overide the final gather calculation with lighting coming from an hdri image of a more unique sky if you wanted, and then just adjust the haze attribute of your physical sky shader if your hdri image is more overcast than clear sky.
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  06 June 2010
^anyone got anymore info on what James said? Tuts would be good, that sounds like what I'm after

cheers
 
  06 June 2010
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