No questions a silly question… that’s up to you 
I’ve been looking at a few tutorials (amoung them the one at Xyz Designs) on how to set up Vray caustics without getting it right… or for that matter.. getting it to work at all 
I would REALLY appreatiate it if someone took the time to either put together a video tutorial or a html tutorial explaining step by step (every step) on how to get the caustics to work.
Waiting impatiently for a reply.
(Using max 5.1 and Vray 1.08 )
any reason your still using 1.08?
prolly hasn’t dl’ed the latest demo or like so many others, doesn’t ever check for updates.
Demos expire, update notifications are emailed…
Let me just jump in here with my 2 cents: you got off the topic, guys Personally, I think that there’s a real need for a straightforward, step-by-step tut for caustics.
So, e_soltani, until a tut is available, try visiting http://www.vray.info and doing a search for “caustics.” I know there’s at least one helpful thread in there. Or, have you tried searching this forum?
If I have the time, I’ll see if I can set up a simple scene with caustics and post it for you to download and study. But I can’t promise anything at this point
Anyone else willing to take a shot?
Here’s a little scene that you can study. Pay attention to the light settings and the render settings:
Download here:
http://www.dtoxx.com/caustics\_tut05.max
I know it’s not exactly a tutorial, but you can glean what you need from it.
First I’d like to thank 586 for you taking time to put together an example file… but believe it or not i encountered a problem opening the file. Just me or anybody else getting an “assertion error”? in file “ParamBlk2.cpp” at line 1885. :?
I upgraded to 1.09.02u advanced.. but the problem stil remains, says something about it beeing corrupt, i dunno. I tried downloading it to a different place on my drive too… but that didn’t work either :?
586, wanna try mailing it to me at e_soltani@hotmail.com?
Thanx!
You’ll need whatever version he made it with or greater, I imagine he used 1.09.03d
I will make a small tutorial when I have the time and if I don’t forget it by monday…
but believe it or not i encountered a problem opening the file. Just me or anybody else getting an “assertion error”? in file “ParamBlk2.cpp” at line 1885.
I didn’t encounter any assertion errors here but I got two other errors, particularly some “Missing Dlls”: ViewportManager.gup, boolcntrl.dlc and RayFXAreaShadow.dlo.
The scene won’t open
I think ViewportManager.gup is a max 5 file. Are you using max4?
Yes, I’m using MAX 4.26. I begin to see where the problem is
First thanks 586 for offering such a toturial ! You’re so kind.
However I also have a problem in opening this files, (the same as e_soltani)
showing msg below:
" Assertion Error Information "
" ParamBlk2.cpp"
" Line 1885 "
(I use Max 5.1 and Vray 1.09.02u)
Roger:
you need to use 1.09.03d
Holy cow! I guess I haven’t been watching this topic. First, I’m VERY sorry for the errors that everyone has encountered. I believe that the problem is exactly what RErender said - you must be using the same version of VRay that I am - and perhaps Max also.
I’m currently running v. 1.09.03d, and Max v. 5.1.0.33
OK. This is my attempt at a tut on achieving refractive caustics.
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1) Create glass material - settings are shown below:
This isn’t an explanation of how to create glass in VRay, so I won’t go into the details of the material, except where the Fog Color is concerned. The color you choose determines the color of your glass, and the multiplier determines the particular hue of the fog color. Lower numbers (like 0.1) will make the glass very close to the hue that you chose. Higher numbers (like 2.0) will adjust the hue downward (such as in the case of the image I posted, the green color of the glass is a lower hue value within the green-->teal range; if the multiplier were 0.1, then the color of the glass would pretty much be the same as the color shown in the swatch). If you need more of an explanation on this, just ask me.
Approximate hue range for fog multiplier.
Fog multiplier set to 0.1 (notice the absorption effect in the darker areas of the torus)
Fog multiplier set to 2.0
Notice also that the fog color also affects the color of the caustics.
2) Apply the glass material to an object (in this case, the torus knot), which for the sake of example sits upon a plane that has a standard grey material.
3) Now for the light set up. I started with an omni, but I didn’t want photons going all over the place and being wasted. So, I chose a target spot. The settings are shown below:
Two things to take note of here: the multiplier and the decay type. These two values go hand-in-hand. For the spot to emit “physically correct” light, the decay type should be set to inversse square, because that’s how light behaves (the intensity of light decreases by the inverse square of the distance that it travels because the area that the light spreads increases by the square of the distance traveled - check out a little experiment with this at Exploratorium) Believe me, any other setting will completely botch the effect.
Now, since we have a light that is decaying and spreading in area in a “natural” way, the multiplier has to be set pretty high in order for enough of that light to illuminat the chosen target. In this case, a multiplier of 20,000.00 is a good place to start. The above images used this setting, and the image below uses a multiplier of 40,000.00:
4) Finally, the render set up. First, make sure that Caustics are turned on in the render rollout.
This first thing I want to talk about is the max photons setting. This will determine how many photons from the spot will contribute to the caustic effect. It basically works like this: the fewer the photons, the crisper the effect; the greater the photons, the softer the effect - as shown below:
20 photons
200 photons
2000 photons
I chose to leave the max photons at 200, since that gave a nice looking result. The setting of 20 was nice and crisp, but also had a lot of artifacts, whereas the 2000 setting was far too blurry.
Next, I’ll talk about the search distance. This determines the max radius for finding contributing photons. I’ll let the pictures speak for themselves:
Search distance 0.1
Search distance 0.5
Search distance 20
In this particular case, values above 20 do not improve the resulting render.
Next, the caustics multiplier. This determines the intensity of the effect independent of the light multiplier. Examples:
Light multiplier set to 5000.00 / Caustics multiplier set to 1.0
Light multiplier set to 5000.00 / Caustics multiplier set to 5.0
Light multiplier set to 5000.00 / Caustics multiplier set to 20.0
Light multiplier set to 40,000.00 / Caustics multiplier set to 0.25
And lastly, under the system rollout make sure that under light settings… your light source (in this case the target spot) is set to generate caustics, under object settings… your object(s) (in this case the torus and plane) are set to generate and receive caustics. Yes, I know that the plane does not generate caustics
Notice also that there are separate caustics multipliers in both the object and light settings. I’ll let you play with those.
One last note: you’ll notice that under the light settings there is a caustic subdivs spinner. This basically controls the accuracy of the effect. See below:
Caustic subdivs set to 100
Caustic subdivs set to 2000
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Comments, questions, corrections are welcome and appreciated 
thats a great tutorial. It needs to be uploaded to vray.info
Thanks I’ll talk to Torg about it.
Thanks for the tut 586..
nice tut dude, thanx .
