[brodie_geers]

Here are some tests I did today. All IBL channels use the same map and the camera is facing straight down on the top of a simple cylinder 1 foot in diameter by 6 feet high (~.3x2 meters). Here's a side view of the setup.



1.

HDRI - Dosch DHB-0006 (I used the largest image, 12,000 pixels wide, to provide the sharpest shadows)



Render



2.

HDRI - 3d world DS360_3DWorld_02. I believe this one is 8000 px wide. If you look in the lower left corner you'll see the shadow of the photographer which is crisp and dark.



Render 1



Render 2 (angled for an alternate view)



3.

HDRI - Home made in photoshop. All black except for one small bright spot in the sky. 10,000 px wide



Render



Conclusion: My conclusion is that IBL with sharp shadows is certainly "possible," but it should be made well known that one shouldn't expect that they can simply use an unaltered HDRI and get nice crisp shadows from it even on a sunny day. It may be possible that if the HDRI were of extremely good quality with a very very large dynamic range to get better results.

If someone has had better results I would be happy to see them.

-Brodie

[Bubbaloo]

It may be possible that if the HDRI were of extremely good quality with a very very large dynamic range to get better results.

I think this is exactly the case.

The reason shadows from HDRI get washed out is because of the light emitted from the sky. So if you've got an HDRI with a sun showing, but the sky is very bright too, that sky illumination will wash out the sharp shadow you want. Try adjusting your HDRI in Photoshop to darken the sky. Use this in the illumination channel, while keeping the original in the other channels. I haven't tried this, but it's what I would try. I've also selected the sun disk in PS and increased the exposure a little bit. This is a good trick.

[brodie_geers]

Yes, that does work. It's an unfortunate work around as it requires a lot of trial and error and obtaining accurate results is quite difficult (assuming it's possible), but at least it's a solution.

The following was made through the method you described I made a feathered selection on the sun and applied an exposure adjustment layer. Adjust, render, adjust, adjust, etc.



-Brodie

[Bubbaloo]

I'm glad it worked for you. Working with HDRI environment is trial and error anyway. Finding or making the right one for your needs can be very tricky. At least this simplifies it a little.

[Mihai]

It's all about the quality of the HDR and the render engine being precise enough to render these sharp shadows. I spent a lot of time looking for ways to create my own hdr environments and with situations where the sun is showing I really tried to go to the lowest exposure my camera allowed to capture the sundisk as small as possible (ISO 50, ss 8000, fstop 20). So I end up with images in this min/max range:



After stitching I get accurate results from this map with no adjustments necessary:



The shadow here looks good, just a little bit blurred like in the real photo, plus the rest of the environment was pretty bright so it's a bit washed out. So you really need a high quality HDR image in terms of exposure covered, not size, if you want to get accurate shadows. To check this, load it up in PS or any editor capable of changing the exposure of 32bit formats and lower the exposure to see what happens to the sundisk. The exposure should change just as if you had taken a photo of the sun at that low exposure. If instead the whole area around the sun just starts getting dimmer you know the map doesn't have enough levels of exposure.

[Half Life]

Try Hyperfocal VHDRI series... nice stuff.

Best,
Jason.

[brodie_geers]

Mihai,

It makes sense that it would require a high quality HDRI to get good shadows. However it's unfortunate that the level of quality/range must be SO great to get passable results. Even in your example, as you say, the shadow is very washed out for it being a sunny day. You'd think that with all things being accurate one could take a high quality HDRI, through it in to the renderer and the lighting/shadows would be identical to the time/conditions in which the HDRI was created.

Do you see this as something that Maxwell may be able to improve over time (as it did with introducing the ability to create sharp shadows at all)? Or do you think it's an inherent flaw in HDRI...perhaps that we'll have to wait for 64 bit images and special cameras that deal much more specifically with HDRI creation?

-Brodie

[Mihai]

However it's unfortunate that the level of quality/range must be SO great to get passable results.

I say it's almost the minimum in these cases The sun is such a strong light source compared to the rest of the environment....The render engine has to be able to sample that range accurately but can't (and shouldn't) invent any data of its own if the input doesn't supply enough data. Like I said the environment of this particular map was pretty bright so with a small cylinder such as this (10cm in diameter) the surrounding lighting and the floor also being a white material instead of mixed rock and darker ground, will make the shadow more washed out.
So it's possible to get good results with Maxwell just the hdr has to have a large exposure range in these situations where you have a very bright, small lightsource compared to the rest of the environment. It's nice to see so many hdr images, many free ones, but unfortunately the general impression is still that as long as it's in hdr format it provides 'real' light.

[JDHill]

Another way of saying: you can record a cassette onto a CD, and it will still sound like a cassette. And there's not much your CD player can do about that.

[sandykoufax]

http://www.maxwellrender.com/forum/view ... 88#p328288

try this.
If you render a exterior scene, you have to make bigger sphere.