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Old 26-01-2006, 04:15 PM   #1
j5ive
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When is HDRI used? I understand it's to give photorealism finishing touches, but when is it used? Ideally always? Only for photorealstic purposes? Animation? Is it memory intensive? Good and bad reasons for using and not using it.

Thanks guys, hopefully your answers will aide me around yet another learning curve!
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Old 27-01-2006, 09:42 AM   #2
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Anyone?
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Old 27-01-2006, 09:55 AM   #3
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Well I have only just started using it so im not the best person to comment. I like it because it can get things to look photo real (if the texturing is up to scratch).
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Old 27-01-2006, 11:50 AM   #4
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Hi j5ive,


Your question is pretty wide dude



what for
HDRI, in the very first approach, helps you setting a much more "natural" variation of lighting. Cause these are directly taken from a real situation/environment. Adding also it helps really producing accurate reflections within reflected light levels, as these lighting points are oversampled within HDRI maps. But also cause you then got a "full env. dome" for reflections.
Usual reflections within a Chrome shader e.g. won't give you a real-looking result, until you set up the HDRI in fact. Car-concept modelers shouldn't show renderings without HDRI. Without HDRI, car paint is just dull. All car marketers play mostly with the cool effects you got in reflections.

Talking 'bout chrome or car paint cause HDRI is mainly effective with reflective and glossy materials, as these mainly exist through a environment. It affects all materials of course, as standard lights would do.

Well, in some way, think about HDRI as a way of not setting up a complex and natural skylight. Just to compare, a normal skylight should be set with different lights colors in order to get a result close to what you get with a simple hdr file.

So, to me, it's used, as soon as you can use it. Cause it pushes all one level up in your renderings. Whatever the situation. As Ambient occlusion does. Once you start with it, you're addicted at first rendering.

Both are keys, as you said, to get improved photorealism.


Memory intensive
Well, I would say no. Well, surely not as much as photons or high sampled depthmap shadows can be I mean. It's just a 1-2 megs file, opened once the rendering starts. So with reflections, it's just as raytraced reflections are, a bit heavy, bot not more cause it's hdr file compared to a scene object. About lighting side, it'll depend mostly on your GI/FG settings.


when
For outdoor modeling, I would say, always.
For indoor, mostly when you got reflective shaders and/on curvy surfaces (cause there's the real killing effect)
And as Tim told ya ... it gives you great preview rendering even with non textured scene. (prevents setting up a 3 point-lighting, which doens't give you a feeling of volume, as hdri does). 3 point light is cool start, but well, you'll notice the diff. quickly.
Also good to know that future VideoGames engine will use it thoroughly. Some engines already do I think.


Animation
WETA plays with it all the time, for sure (I-Robot, in every frames).
PIXAR and Dreamworks don't need it at all, but prolly use it (sss is much more usefull with a Shreck or Tilt than some hdr map).
So it depends on the realism and look needed.


Good and bad reasons using it, or not
Lol, that i can't objectively answer. I love HDRI too much. All I can tell so far is that I quit another modeling tool cause I really needed HDRI badly. So my reason using it relies more on a soft dealing correctly with it.
It's also not producing sharp nor accurate shadows.
You'll just get some ambient occlusion effect, through the FG, but HDRI shouldn't be used without any real shadowing light for a real looking rendering.


Hope you got usefull infos in there.


Try it, love it, adopt it

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Old 27-01-2006, 12:05 PM   #5
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Thanks a lot for taking time to write out that reply Pyrus, that was a great read and excellent help. I'm satisified with my modelling and texturing for now, and want to get into 'showing' off my models with a good standard of rndering, which you have helped me greatly to understand. Thanks again!
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Old 27-01-2006, 12:12 PM   #6
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My pleasure dude.

Don't forget deactivating default light in MR setup (as GI/FG) ... and also hiding all of your lights. Then activating them one by one, with low values, step by step raised. Or you'll end up, as often in very first times, with a white penciled like rendering

Also, don't go through std IBL node at first, but simply apply the HDR on a sphere. This way you can control the Y rotation of the sphere and get your light-samples, visually, in the viewport, where you want them (in place of rotating your model) ... back, front , side.

I posted many sources on a previous thread about hdri in this area too. Last week I think.

Have fun
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Old 27-01-2006, 12:43 PM   #7
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Yer I actually found that pretty useful. I am positive that my next WIP will include some sort of HDRI to bump up the quality.

At this current moment I am just an information sponge trying to learn the most I can about it.

Cheers for the info.
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Old 27-01-2006, 01:41 PM   #8
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Yeah Tim,


I can't wait for the HMS with a cool warm sunset light near a simple island .... and huge oil sea.

This amazing piece of detail you modeled deserves the best fit hdri.

Hehehe :attn:
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Old 27-01-2006, 02:24 PM   #9
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Well I did try to put my model in an HDRI setup (before my pc went tits up) and it wasn't having none of it.

I will try again more seriously when I get my replacement motherboard (they said I would have it today) :angery:
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Old 30-01-2006, 03:48 PM   #10
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When searching for FG/GI ressources, I found that step by step guide. It's about importing a solidworks model in fact, but scroll down a bit, and there's a comprehensive guide for HDRI.

Well, seems many problems arise through oversaturation.
And i've read about some explanations telling this was due to a Pi division, not implemented, which causes this overvalues in lighting.

Dunno if it's true, btw, 't seems being a good starting tip for HDRI gamma correct (file gamma correct).


Hope this will help


(maybe to mention I didn't need gamma correct though under v7)
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