Iray and HDRI
evilded777
Posts: 2,466
So, there's all kinds of glowing reviews of Iray using HDRI lighting. Some users say its the only way to go.
For me, meh. And I'm wondering why that is. I've gotten some results that I am pretty happy with using photometrics and emissives, and using the Iray's sun and sky lights.
But with a variety of HDRI maps, I have the same mediocre results. And since I am the common denominator here, that leads me to the conclusion that I am doing something wrong.
I've used a variety of Dimension Theory's maps (and before someone chimes in, I do know to use the EXR files not the jpeg) from the HDR Pro Sets, the Reality Skies (these give me the worst results... try to get a night sky to look like night... not happening), maps from the sIBL people and other ones from around the Internet; all with the same mediocre results.
I use either the Dome and Scene or Dome Only setting in the Environment tab, put the HDRI in the Environment slot and that's basically it. I adjust nothing else. I have tried Infinite Dome, Finite Dome (there's something really wrong with Finite Dome... yellow cast to the dome, green cast to the ground), even the cube.
What am I doing that I shouldn't be, or not doing that I should be?
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Comments
HDRI lighting in Iray does seem to be a bit of a black art. I've done some experiments with adding the Yosemite 11 and 12 HDRIs to the environment channel on an Iray sky dome and I seem to get lighting which is still too dark, even after fiddling with the dome rotation.
The best results on the 12th HDRI seem to come with a rotation of 0 or 180 degrees. The background looks washed out but the foreground is too dark.
Cheers,
Alex.
My (limited) experience is that most of the HDRI we're likely to have is best as a somewhat out of focus backdrop or a background ambient lighting, and then use actual spots/points/glowing objects in the scene to drive the primary lighting.
That's not horrible, Alex... but you're right... the image that the light is based on is way too bright.
Personally, I'm not sure I would ever do the 3d model in front of backdrop like that and call it done (not suggesting you would, either). That's just not my style (although, a lot of the car/mortorcycle images that proliferated when Iray was brand new did look awfully slick).
That being said, it sure would be nice if we could have some sort of predictable result... or else we are back to the old issues of just throwing more damn light at the thing until some of it sticks.
I don't see why that would be the case. They may not be of the quality of some of the giant images out there, but they do a pretty respectable job in 3Delight.
And I personally don't expect it to be my sole light source (though I can pretty effectively use sun/sky that way and some people do tout that hdri is their only light source), but it would be nice if it was at least somewhat predictable... which, for me at least, it currently is not.
I do understand how to rotate the image, and where the parts of it are going to be, but that seems to me to only be a fairly small bit of the battle as when I load a night sky HDRI and it looks like a blue sky noon.
So what does the Slider on Environment Map actually do? It has a default of 2, with two default colors: blue over gray. What do the colors do?
What does Environment Lighting Resolution do?
What about Environment Intensity?
I'm a bit sad to see that this thread has not received any reply from someone who had deciphered the magic to make HDRI lighting work in Iray. I've been playing around with the dome and it's settings since the beta was first made public, and so far the magic eludes me as well.
I'm rather disheartened as well.
But at least I found some answers to some of my questions.
Environment Intensity: A linear scale that is applied to the intensity returned by the environment (huh? Makes it brighter or darker)
Environment Lighting Resolution: I don't even want to type the definition of this, because its another physics problem. But this part is handy: Higher resolutions result in more detail in the visible environment and sharper shadows if bright details of the environment function are small. (So, in other words, crank it up some if you feel like you are not seeing the details/shadow you expect out of the hdri).
I don't have any of the sets you mention, is there a common IBL we can work with?
I suspect the main reason for inconsistent results is that not all HDR files are created equal.
Some will have a dynamic range that is barely more than a jpg, while others go all the way to eye-melting (that's a technical term!)
Well, there's a number of free images at the sibl archive http://www.hdrlabs.com/sibl/archive.html
I have downloaded most of them, though not gotten much use out of the yet.
I have made some progress, and starting to think that my issues were not so much the HDRI component but my skin materials that were lacking.
HOWEVER, I still see unpredictable results... so plan to continue to investigate.
In one of the other Iray threads someone posted a link to a HDRi of the Pixar campus. Mec4d has been using that one in a lot of her renders, she's posted.
The way I look at it is, if you are going to use IBL, use an image that is going to provide enough lighting information, by itself, that no additional lights are needed. Yes, you can add more lights...but for accents/effect rather than making up for deficiencies in the 'base' lighting. To do that you need very high range HDR images.
Some links to high quality HDRs (Usually much higher than the sIBL archives...though there are a couple there are very good...the DutchSkies one, for example)
These have very high dynamic range and will cast sharp to very sharp shadows with no additional lights.
For non-commercial use
http://www.aversis.be/hdrin (Averis also has for sale ones that are usable for commercial renders)
http://www.dylansisson.com/project/panoramas/ (this is the home of the Pixar image)
These are medium to high quality (many of them can cast good shadows with no additional light sources) and may be used for commercial renders...
http://adaptivesamples.com/category/hdr-panos/
These are medium to high and have a mix of licenses, most of the free ones are non-comm...
http://www.openfootage.net/ (most of the descriptions include a render showing what the shadows will look like)
****Another edit*****
I've used a couple of the Openfootage images and one of the Averis images in Luxrender, 3Delight and Iray with very consistent results among all three. No I don't have any images to post...sorry. And for 3Delight, I don't use the UE2, but rather 3DL's Envlight2, Mustakettu85 has a tutorial on importing the 3DL Envlight2 into DS.
The same image, if high quality, should give similar results in any renderer, with minimal fuss and bother.
I have an odd question i'm still trying to tinker with the iray stuff I went to http://www.hdrlabs.com/sibl/archive.html and tried using the milky way one and frozen waterfall. Since they were dark i assumed it would be a darker as well so i added in some lighting to go around the figures but non of the lighting shows through. I'll do another one tonight and post it so you can see what i am talking about.
There are two primary reasons for using an HDRi, and the reasons can complement one another, or can be used on their own:
1. Providing lighting for the scene. This requires an HDRi engineered to provide a reasonable amount of light, in the right places, to act as a natural light source.
2. Prividing a backdrop for the scene. Here the HDRi is basically a pretty picture. That's fine, but it may not provide enough lighting on its own to produce good modeling. You need scene lighting to augment whatever illumination the HDRi is providing.
When you post your images please also note your render and Environment settings. If you choose Dome Only, you wont' get the effect of the scene lights. You need to choose Dome and Scene, and you need to be sure the scene lights are set properly to cast sufficient light.
When setting up lights, try to follow a common workflow:
1. Be sure to use a new camera for rendering. Don't use any of the Views (e.g. Perspective). These are not true cameras, and lack the full camera controls.
2. Turn off the camera headlamp so it doesn't influence the lighting in your scene.
3. Set up your HDRi environment first, before adding scene lights. Do some test renders. Don't worry if you can't yet clearly see your figures.
4. Switch to Scene Only (the HDRi is now turned off), and add one light at a time. Adjust toprovides the light you want.
5. After each light added, test all the lights together. Lighting is about balance, so be sure to fine-tune each light source with respect to itself, and the others. You can turn individual scene lighrts on and off to better visualize the contribution each makes to the scene. (The more you do this, the easier the light setup will be. After a time, you'll just know what works.)
There has been some comments that "The more lights the merrier in Iray." This is not really true. Iray has a penchant for light, not necessarily light*s*. First off, just adding a bunch of lights willy-nilly isn't how you illuminate a scene in the real world, and it isn't in the virtual world. Each light needs a purpose. Second, all things considered, for each light you add, Iray must do separate ray tracing calculations, and this adds extra render time. Iray does render faster with more lumens on the scene, but that can come from just one or a couple of well-placed sources.
The moral: keep it simple, and if you need more light to get a faster render, first try boosting the output of what you already have. You can increase or decrease the lighting from the HDRi using the Environment Intensity control.
Why can't we give positive press to people who write great posts like this? A simple Thumbs Up or what have you.
Succinct.
I've found this to be helpful.
http://docs.daz3d.com/lib/exe/fetch.php/public/read_me/index/21981/21981_quick-start-guide-to-the-iray-dome-and-the-use-of-hdris.pdf
My problem before I can even jump into the colors of the HDRI bg is the distortion I get. I've never been able to fix it. Anyone have any answers?
For distortion free BG...you need a MINIMUM 20,000 x 10,000 preferably larger and still probably need to use it with a finite dome. 10,000 x 5,000 is the minimum for minimal distortion with a scaled finite dome.
ENVIREMENT LIGHTING RESOLUTION
Here, I used one of the 8k HDRI from adaptivesamples and no other lights. The only thing I changed was I lowered the Exposure Value in Tone Mapping on the Render settings tab from 13 to 12.25 (making the image brighter). I think it looks great. I didn't optimize anything in the scene tho, which I usually tweak the surfaces on EVERYTHING. This was just a quickie. LOL.
Laurie