Here’s another popular question I frequently hear: My scene looks fine with the mrSun/mrSky system but when I use a HDR it’s black. Does mental ray, iray, vray, whatever-ray not support HDRs? If this has affected you, read on for the most common explanation.
I’ll go ahead and warn you now, this is one of those topics that may get kinda fuzzy. My primary goal here is to explain why HDR/EXR files may appear dark in a scene. To start off let’s say you have a scene you’ve created and now you’re ready for lighting. Typically a couple of common scenarios happen at this point. You may add a daylight system with the mrSun/MrSky/mrPhysical Sky combination or jump straight to a HDR/EXR for illumination. To begin with, let’s assume you start with the daylight system/mrSun/mrSky/mrPhysical Sky.
You fire off a render and get something like this:
Of course there will be slight variations to this based on your sun locations, etc. Anyway, nothing wrong with the lighting setup here, especially if your goal is a clear sunny day. However, after checking out your model in this type of environment you feel that you’d like to use a HDR/EXR file for the lighting instead of the mrSun/mrSky/mrPhysical Sky. You assign the HDR/EXR file to the environment and/or a skylight or whatever method you choose and fire off another render and get this:
What the….
What went wrong? In a word, exposure. Your exposure control is configured for a very bright daylight scene. Like this:
Typically, HDRs/EXRs that you have purchased or made do not default to the same intensity as the 3ds Max daylight system. If they did they would probably be pure white when you viewed them in a typical image viewing program. To help visualize this, if you disable the mrPhotographic Exposure control you’d probably see something similar to this if when you render the mrPhysical Sky vs. a HDR:
The mrPhysical Sky is super bright whereas the HDR/EXR looks spot on. Now if you enable the mrPhotographic Expsoure control with the outdoor daylight setting you’d see something like this:
Now the mrPhysical Sky looks right, but the HDR/EXR file is waaaay under exposed. What to do? Well you have a couple of options but basically you can either adjust the exposure control settings or the output/intensity of the HDR/EXR file to give it the proper intensity value.
For example, keeping the mrPhotographic exposure on Outdoor Daylight preset but with the HDR file instead of the daylight system I could use the unitless physical scale value to compensate for the HDR/EXR intensity like this:
A render with that yields this:
Yaay! Now the HDR/EXR file is visible. BUT…there’s always a but right? This setup isn’t a global setting that you can or should always use. I say this because at 90k the exposure settings are waaay to high for the time of day of this particular HDR – (dusk) environment. A problem would arise if I were to use this setup and wanted to add some lights to the scene I would need to boost their intensity unrealistically high before they would be visible at an exposure control EV value of 15.
How do you know what exposure settings to use with any HDRs/EXRs then? Well, that’s the rub here since HDRs/EXRs are built from multiple exposures and taken at various times of day in various conditions, etc.. Hard to nail it down to one exposure value, especially so if you plan on adding other light sources to your scene.
There’s one ‘trick’ that I use though. A lot of the HDRs/EXRs I have came with backplates. Those backplates are typically exposed properly and you can use their EXIF data to obtain a working exposure value.
In windows I can view the file properties of an image and in the details section easily find the camera info like this one that came with the HDR I used above:
With that info in hand I go back into 3ds Max and enter the Shutter Speed, ISO, and f-stop info into the mrPhotographic Exposure control.
Then I can adjust the unitless physical scale value to something that provides a close approximation to what I’d expect. For this particular HDR file 12,000 seemed to be fairly close to what I’d expect.
Of course it’s still a guesstimate, but with the backplate shutter/aperture/ISO info plugged into the mrPhotographic Exposure control I feel it’s somewhat close. It should also provide more realistic results when lights are added to the scene (like IES lights).
So the bottom line here is that more than likely if you’ve tried to light a scene with a HDR/EXR file and it turns out black or overly dark it’s probably because of a conflict in your exposure control settings and the intensity of the HDR/EXR file. You can adjust the exposure settings and/or the intensity of the HDR to help resolve the issue.
As with anything in 3ds Max there are many other ways to tackle this. I’m not in any way saying this is the perfect method, it’s not really…but it works for me and the scenes I work with. You may have your own preferred method for accurately adjusting the intensity of the HDR/EXR files for use with exposure control like not using exposure control at all and rendering out in linear format, etc..
NOTE: For the example images posted here I used an Evermotion scene.
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Great article Jeff, I’ve come to use your method over the years, seems to do the job and that works for me.
Thanks Jeff for sharing…
The first tip of 2012…
Happy New Year bro…
Thanks Jeff,
Your tips are priceless!
Hi Jeff
I was trying to use HDR images to dom some nigth views using “Iray” and this explanation about Exif of HDRI whit this method to correct the Phisical Scale, worked very well to me. Thanks for share your knowlege again.
Jeff, good tips and ideas as usual. What do you think about increasing the output of the HDR to a point that gets the scene to the proper exposure without tinkering with the global scale? Just curious. I am anxious to try out your method tomorrow. What are the repercussions of moving away from physical units. Architecturally it seems like you would lose the true value of, say, a 60 watt light bulb. Cheers!
Changing the physical scale on the photographic exposure control over to unitless shouldn’t affect the actual lights in your scene. That 60 watt photometric light source will still have the same intensity. What will be affected is things like the environment map and self-illuminated materials.
Oddly enough, when I try your method, and go to unitless (and I should mention that I did have some self illuminated materials at play), it caused my CUDA device to crash with memory issues. I am running GTX580 w/ 3gb of RAM.
Make sure your self-illuminated materials are not reflective and have no diffuse. That can sometimes lead to a problem in an over-bright situation.
hi, i can create the light, but you have shadows from your hdr, wich i cannot have, what’s the trick to have the feel that there’s still a sun lighting the scene?
No trick that I know of. Just use a HDR with a strong light source(s) and a fair amount of lighting data (EV steps). Just like with area lights, larger diffused light sources in a HDR will produce softer shadows than a HDR with small/bright light sources. See THIS older post for more info/examples.
I am trying to get ibl light in mentalray with help of this tutorial
http://www.infinity-vision.de/page/ibl_mode but i am no able to find ” 3. activate IBL – Mode ” could you help me and if possible could you create some example file,thankyou.
hi iam javad from iran
az all tank you
iam archi
Hi Jeff,
Thanks again for this wonderful tip, will try it out very soon! I used to compensate the brightness difference with the HDR’s output value like Josh Pabst says, it always worked well for me, but your way feels more natural and logic to correct somehow.
Anyway, thanks again!
great works, thanks…
Jeff,
which method of utilization do you prefer/recommend for using hdr/exrs? Do you use it alone in the BG slot, a mr sun/sky combo with the hdr/exr in the BG slot or a mr sun/sky combo with the hdr/exr in the mrPhysical sky shader?
wow .. very useful tips .. in my previous, usually i increase the output value of its HDR image.. but, i should turn off the exposure control in environment setup. i though its just the only way, but now i can try your tips .. really useful .. thanks sir ^^
Hi Jeff,
i have a question. No matter what i do, i don’t seem to get any shadow in my render while using an HDR for lighting.
I put a nice (so i think) HDR in the environment map, exp 13, unitless 30000. And it does light the scene, but there are no shadows anywhere. Can it be the scale of the scene? (units: system and display in meters)
There are no other lights in the scene then the hdr. I also tried your free HDR, but with the smae results,
any idea what i miss?
thanks,
Oswald
Maybe you’re using mental ray (you didn’t mention what render engine you’re using). If so, then that’s to be expected because the mental ray connection in 3ds Max is simply horrible at producing shadows from HDRs. For mental ray to produce shadows from HDRs with bright lights it requires users to do one of the following:
a. Use light sources for shadows.
b. Use optional calculation methods that users have to install/configure on their own.
c. IBL works great for HDRs, but of course that’s not directly exposed in the 3ds Max / mental ray connection. You could try THIS for IBL and/or see THIS thread also.
It could also be that you’re using the matte/shadow/reflection material and expecting to see shadows on it? If so, then you’ll need to use light sources for that OR it looks like the IBL method outlined above may work with the M/S/R material.
oops, sorry Jeff,
yes, i use mental ray, have to make an animation and i don’t have a good grapghic card to make it interesting to use iray unfortunately.
i’ll look into this IBL,
thanks for your quick answer clearing out that it’s not all my mistake
just looking for a very fast way to light my outdoor scene for a 4000 frames animation. So i thought while using an HDR for lighting i don’t need any other light sourse
thanks again, i’ll jump into it
i have a small other question:
i have this 4000 frames animation and when in MAX2012 i want to precalculate the FG-map, it takes max 1 minute 14 sec. per frame. The biggest problem is translating scene, that takes ‘ages’
When i take the same file into MAX2010 it takes 14 sec per frame. reuse geometry doesn’t make a big difference btw.
Afraid I don’t have any personal advice on that one. Search the AREA site, seems like I remember a discussion there (or possibly it was CGtalk) about the increased translation times.
Hi Jeff, I’m new in 3ds Max and I’m trying to light up a scene using iRay, although my scene is lighted with the HDR (with adjusted exposure values and unitless physical scale) I still can’t get any shadow from it, even if i use photometric or target lights on my scene. I only seem to get my shadows when I use mrPhysical Sky environment.
If you mean you can’t get shadows from the HDR then it’s probably because the HDR doesn’t have well defined light source(s). See THIS article for example (including the comments section).
Dear jeff i want to ask you something when i use daylight in mental ray it doesn’t give realistic output. on ground it show’s more light. i jst need output as we get in skylight i mean how can i get clay render with daylight in mental ray ( on exterior)
Not sure I completely understand the question, but if the sun is too strong then decrease its intensity. Or if the skylight is too strong its intensity can be adjusted as well.
Adjusting the Camera to match the HDRI is an interesting method. I’ll have to try that myself. In V-Ray I have always adjusted the multiplier for the HDRI – but thinking of it, matching the source background makes sense.
hi,
I am new to mental ray I have been visiting your site over the past few days.
great stuff..I have learned lots in just the few days i have been on and off the site.
a quick question, Do you have a mental ray interior rendering tutorial lot with a HDRI map only. I have been searching the net and for the life of me i cant find one.
The reason why i am asking the above. I have been thrown into the deep end. I am currently busy with a 3d. I am sitting on the inside of the building looking out, on the outside the building has a sea view and some greenery.
I became clever and told my boss, don’t stress ill sort it with HDRI lighting….well I am stuck.
Any ideas or even quick tutorial by yourself will help lots.
Basically I’d just assign the HDR into the environment and add some portal lights to “push” the HDR environment into the room. Here’s a quick version of the bathroom scene setup with one of my HDRs for reference:
Render Output
.MAX scene
cool<
i assumed its based on the bathroom tutorial you did earlier….i go through it and forward any questions that come up.
ally