Iray HDRI shadows too soft
nickalaman
Posts: 196
Hi,
I purchased some HDRI files for use in studio with iray. They work but the problem I find is that the shadows are very soft and diffuse. The same HDRI used in octane gives me a nice crisp shadow, so i know it's not the hdri, is there any way to imporve this in studio? I've never been able to get crisp shadows using HDRI with iray. Any help would be appreciated.
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Comments
Have you tried the shadow intensity slider at the bottom of the environment tab. There is also the crush blacks slider under tone mapping. I don't know how an HDRI works in Octane, it sounds like it is used as a distant light, but in Iray it is an environment light which is an ambient light. Even with a strong light source in the HDRI the shadows will be soft. Increasing the environment map, or dome, slider and lowering the settings in tone mapping to compensate might increase the shadow but it still wont be sharp. Using either a spot light where the sun is in the HDRI or a distant light will sharpen the shadows too.
Proper HDRI images used for IBL in Iray WILL create sharp crisp shadows when they have intense small lights sources caught in the image (like the sun.) A lot of what is available as HDRI images are NOT full depth, and lose a lot of the intensity levels to conserve size (as most HDRIs are very high resolution to begin with...) so this tends to wash out the intensities. Also, make sure you have your tone mapping and camera parameters right.....these can have a huge effect on how the lighting looks.
If they are good HDRIs, try bumping up the environments strength. If everything washes out evenly, the HDRI doesn't have correct intensities. If the bright parts become brighter considerably more than the rest, then adjust your camera parameters to compensate and voila....
Hi,
I've tried increasing all sliders, inclding the ground shadows, but still no difference. (or atleast very subtle) If the HDRI image has a sun and is exposed properly you should get real looking shadows from the point light source in you HDRI.
Try some from some of the links in my sig. HDRIHaven has a set of 5 very good, large ones that can be used for both light and backdrop. There are others, like from Aversis, too.
The interpretation of the magnitude of values in an HDRi may well be different in the various renders. In D|S, there are scant user controls for manipulating how the renderer will interpret the values, in a similar way you'd use the Curves feature in Photoshop. Since gamma plays a role in interpreting any HDRi, you might try playing around with gamma settings of the file, using a graphics editing tool that can handle 32-bit TIFs, EXRs, or HDRs.
For that matter, be sure this HDRi is 32-bit. You can technically load an 8-bit image as an HDRi, and it can even cast a very strong light for a delineated shadow (see below). But the HDR is capped as far as its dynamic range is concerned, leaving less latitude in adjusting other lighting aspects. I had to increase Environment Intensity to 100, for example, to increase the light to a more suitable level.
Thanks,
I will try adjusting the gamma in photoshop, in see what happens.
Nick
I tried adjusting the gamma and it still did not make a very big difference, it's like once you load the image into daz, it loses it's dynamic range and studio turns it into a jpg. Look at the difference, this is either a bug or just plain lousy programming. The iray version is the one with the black bathing suit. Notice the highlights on the skin, the shadow on the ground. The iray version is dull. And has just a trace of a shadow. It’s like I fed it a LDR instead of a hdri file. Studio must be killing the hdri file once loaded, this is the only explanation for such a big difference.
I know studio is free, but this really should work, I’d pay for it if need be, but as is the HDRI is broken.
Thanks,
Do you mean the black bathing suit? To my eyes, the example with the white suit is showing distinct shadows.
Don't take this the wrong way, but both renders are fairly poor. I don't know what your end goal is, but even though you may be getting good results in a particular renderer, doesn't mean your HDRi is quality. I'd try a few others that are known to be good -- i.e. demonstrated in other threads here -- before making a determination. How about trying the good old Pixar Campus HDRi available from Pixar. It's free for non-commercial use, and a good example of how HDRi functions in Iray.
As I showed by example, it's quite possible to get strong, distinct shadows in Iray using even an 8-bit HDRi. With 32-bit it's better, and the shadow detail can be quite good.
you're correct. I meant to say the black bathing suit is the iray version.
these renders are not suppose to be anything but a demontration on how the same hdri image is interpeted by octane vs iray.
i will try ther pixar image you mentioned.
Nick
deleted.
What I meant (as an example) is that unless you've turned on DOF, the HDRi is quite blurry in both versions. Maybe Octane has some different HDR tuning that works around this, but in general, the softer an image in Iray, the less distinct the shadow.
The gamma is quite different between these renders. It could be in the HDR, or the output image, or both. It's pretty obvious in the contrast and the color saturation that there may be workflow issues going on.
Refer to the first part of the following page for some insight on correctly using HDRi's. There are similar blog posts here and there with other useful information.
http://blog.irayrender.com/post/14310848190/physically-plausible-scene-setup
these renders are not suppose to be anything but a demontration on how the same hdri image is interpeted by octane vs iray.
I did use a DOF on the camera, so that should not have been the cause.
I did download the pixar campus hdri file, and it worked wonderfully with it. The only difference i noticed with the pixar campus file was an EXR vs HDRI. So i downloaded a few exr files from the web and noticed all worked as should, can't say the same for HDRI format, most did not work. Not sure why, becuase the same files worked in Octane. So i'm guessing there is some type of incompatibilty with some HDRI formats. Will investigate further.
Thanks for your help!
(Edited)
Try these HDRs. They could punch through lead plate.
http://giantcowfilms.com/2015/11/23/hdr-morning-sun-winter/
Iray can use most any file format for an HDRi -- EXR and HDR are fairly interchangeable, as are 32-bit TIFs, which are the basis of the HDR format. Pixar is more likely to use EXR, as that's an open standard, avoided some now expired patents, and is promoted by their pals at Industrial Light and Magic.Actually, they both work for the Mouse now, so it's all one big happy family.
There's a tutorial available about how to tweak "weak" HDRi's in Photoshop. I case you want to use that specific HDRi for all sakes...
That turorial was great. I was able to correct my HDRI files!!!
Not only that, but with this tool I think you should be able to convert any jpg to hdri by adding a sunlight or modifiing existing lighta to increase there exposure..
Nice to hear it helped.
A proper HDRi really can't be replaced by a LDRi/MDRi, and one has to be very careful not to smuggle a too high EV into them. If your backgrounds sky is heavily overcasted, with no sun disk visible, shadows shouldn't come ot crisp. I'd use that method only on weak "HDRi's" if the sun is clearly visible on the sky but shadows turn out weak.
There are many images out there advertised as HDRi which in fact really aren't one. High resolution alone doesn't make an image a HDRi. I hope one day those people will learn the difference.