Ever wanted decent shadows from your image based lighting scenes (HDR)?  Well, it's possible if you use Irradiance Particles in 3ds Max/Design 2009.  Read further to find more information & files.

I'm sure by now you've seen the posts on using Importons & Irradiance Particles in 3ds Max 2009.  So in this post I'll assume you've already installed the required shaders.  If not, then you'll want to go here first:

http://forums.cgsociety.org/showthread.php?f=87&t=621727

Once you have installed the items provided in that link all you need to focus on is the Irradiance Particles.  In a nutshell, you'll disable the default lighting, assign your .HDR to your environment as normal then activate Irradiance Particles and enable the Environment Evaluation option and finally tune the ray settings to suit your scene.

Example:

The render above is not using the interpolation option on the Irradiance Particles.  Therefore it'll be a bit more accurate, but will also have more grain which will require higher samples and that means longer render times.

So, you may want to use interpolation to help keep render times down by sacrificing a bit of accuracy.  In the following render I used Interpolation:

I used one of the default .HDR's that shipped with 3ds Max 2009.  While I simply plugged the HDR into the environment (I probably wrapped it in a gamma/gain shader as well), you may want to consider using the environment/background switcher to use a low-res version of the HDR for the lighting & the higher resolution version for reflections.

Doing so will allow you to use lower samples, but a small blurry HDR will also not provide as much lighting detail as a high resolution version.  So as with most everything, it boils down to a trade off between accuracy and render times.

Test scene: *removed*

Notes: For a detailed explanation of the Importons & Irradiance Particles settings, see the "ctrl_ghost_settings_v1.2.txt" file that comes with the shaders.

I noticed that when I saved the file, restarted 3ds Max and reopened the file, often the Importons option would be enabled...even though I had it disabled.  So if it's enabled when you open this scene you can turn it off or leave it on, doesn't really matter for this scene since there's no active lights.  Speaking of lights in the scene, you'll see a disabled skylight...that's simply to ensure the default lighting is off.

Don't forget you can save the IP calculation by entering a save to path in the "File" box of the IP settings.

NOTE: One can also get shadows from .HDR files via final gather, but it may require:
1. Fairly steep FG settings.
2. Setting the "noise filtering" FG option to "none".

Blog entries may be discussed in the 3DA forums HERE

TrackBack URI for this entry

Comments (12)

Subscribe to this comment's feed

Kristian Foshaug wrote on September 10, 2008

Title: exposure control Thanks Jeff, I tried to copy what I saw, and no matter what I did, I would only get a completely black scene. Not until I went deeper into your scene and tried to copy every small setting I could find that was not exactly like in my scene. I noticed that you had some kind of glare-shader active in your output (defaults off), but it didn't have anything to do with my renders, still all black. Then finally (after giving up really), I noticed that you had heavy exposure-control on (EV -2), and that did the trick report abuse vote down vote up website Votes: +1

Juan Gea wrote on September 12, 2008

Title: I support you This comment os not for this post, is for the post talking about that you are going to leave the 3D as your way of life. You have all my support, i think like you that are the 3D community are like brothers and sisters, olders, youngers, but when i see someone that needs to work in another thing that is not what he/she likes something dies inside me. I hope that you find some work inside this bussiness, you are really great with lighting and render, maybe you cannot continue like freelance, but i'm sure that you can find a job inside somewhere, and in some time return to the freelance world. Really, you have all my support and i hope you can find something. Juan Gea report abuse vote down vote up website Votes: +1

César Garcia wrote on September 15, 2008

Title: Real IMB Amazing post Jeff, finally after many years playing with HDRI files for reflection we are able to render a real IMB without need of other lights. The main problem with IMB was exactly this lack of shadows... bwt I miss your frequency of posting dude cya and thanks again to share this knowledge report abuse vote down vote up website Votes: +1

easyfrog wrote on October 01, 2008

Title: JP I want ask your same questions about FG interpolate Sorry for my English first in my test i find the FG radius interpolate is better then the FG point interpolate . Could you tell me it is right? and why?? report abuse vote down vote up Votes: +0

Tim Wetzel wrote on November 22, 2008

Title: ... When I try to run your file, I get this error in the Mental Ray dialog: RCGI 0.3 error 361060: failed writing IP file It also takes forever to render and I have a pretty good machine. report abuse vote down vote up Votes: +0

Jeff Patton wrote on November 22, 2008

Title: ... Sounds like it's simply not able to write the file to your hard drive. Ensure you've specified a valid path & file name and that there are no firewalls or windows login issues preventing 3ds Max from writing the file. As for the speed, I never said this file rendered fast. However, I did offer very specific information that could be used to decrease the render times if needed. And naturally once it can read the data from the IP file it will render much faster than the original calculation. report abuse vote down vote up Votes: +0

Tim Wetzel wrote on November 22, 2008

Title: ... thanks in the time between me posting this and seeing your reply - I got it working. Couple of questions if I may. 1. If there is nothing animated other than the camera, the IP map only needs to calculate once, right? Sort of like the radiosity light system. 2. I just gave a file name "test" for my test above. what does the extension end up being? 3. Is this calculation the same as radiosity in that if something in the scene changes such as materials or reflectivity = that the IP has to be recalculated? Thanks! report abuse vote down vote up Votes: +0

madcap66 wrote on January 15, 2009

Title: Where to place "ctrl_ghost_settings.dll"? Where exactly does one place "ctrl_ghost_settings.dll"? Thanks report abuse vote down vote up Votes: +0

Peter Blackearth wrote on October 19, 2009

Title: EV = - 2, because? 10x u, Jeff, once again for the great tread :) what i can't get is, why would u use EV = -2? What's the point here in relation to the whole idea for a "physically correct" rendering? report abuse vote down vote up Votes: +0

Jeff Patton wrote on October 19, 2009

Title: ... "why would u use EV = -2? What's the point here in relation to the whole idea for a "physically correct" rendering?" - In this blog entry I'm merely illustrating how IP can produce shadows from your .hdr files. The included scene is not meant to serve as a guide/template/sample for lighting a scene and/or exposure settings. EDIT: I can see how it may do more harm than good to provide a file in this particular case so I've removed the file. report abuse vote down vote up website Votes: +0

Peter Blackearth wrote on October 20, 2009

Title: After all, it's all about results! I wouldn't say teaching us one or another lesson could make any harm! I quess i haven't formulated my question correctly! Maybe you are not the one I should ask about it, but i was simply wondering: IBL was ment to give such a result (descent shadows) when ussing Irradiance Particles. And it certainly does what it was ment to do. But then, again, with all the physical workflow of applying gamma corrections, exposures, using HDRI-s for lighting and stuff, how fo we come to using negative exposure for both the environment and the geometry itself, instead seeting the real exposure values for the actual IBL Situation (sunny day, sunset, night or whatever we have as a HDRI). What I was actually wondering was if it has physical sense of setting the exposure this way (which is everything else but not intuitive or straightforward, and i would never find it out on my own), or as I said it's all about getting the aimed output. After all i have my answer, 10x to u! No matter if it was ment to serve as a guide/template/sample or whatever it gives us the option to create image lighting based shadows, which is great! Thanks again for sharing! report abuse vote down vote up Votes: +0

Benjamin Schiefer wrote on February 25, 2010

Title: ... Hmm, the images don't show up. Seems the links are broken :( report abuse vote down vote up Votes: -2