"Caustics through Mental Ray" in Max2012 - help needed

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Hello everyone

I'm trying to recreate the result from this tutorial http://www.cgarena.com/freestuff/tutorials/max/caustics/ in Max2012 using A&D materials, but no matter what i do i just can't get any useful result. Tried low and high photons and sampling combinations with no luck.

 

This is the render without caustics:

 

 

 

And this is what i get with 8 milion photons and energy on 500000:

 

 

What am i missing? Here is the file itself if anyoune could have a look at it to see what needs to be done. Thanks in advance!

http://www.box.net/shared/bs6x2hxcd0duvpqec3l6

[Braiz]

I would like to venture a guess before I take look at the scene.. Are you using area lights/portals to light you scene?

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I would like to venture a guess before I take look at the scene.. Are you using area lights/portals to light you scene?

 

No, photometric lights for direct and indirect illumination, and one invisible photometric (sphere) light just for caustics.

[Braiz]

Well that is what i mean by "area light" I assume you are using the photometric light with an area shape??

 

And since you are using a photometric sphere, I would suggest you used a omni instead, or lower the size of your sphere shape. Turn of shadows, disable "affact diffuse" and "affact specular", and remember to set the light to generate caustics

And crank up the intensity!

 

Try it...

[Braiz]

I just did a test with your scene... the intensity of your area omni (not sphere) was set to 0, so it had no effect on the caustics.

 

So if you do what I mentioned, it should work fine

Take a look at the render.

 

I will try and build the scene from scratch, because it renders paintfully slow. Just to make sure, that we are doing thins right, hope that's okay? You can get the scene when I'm done

[Braiz]

Here is the final render with 600000 caustic photons. still pretty slow, but it works. It's completely based on the old caustic tutorial. I'm guessing you've also used that tutorial as reference.

 

Tell me if you want the scene file and I can attach it...

[Braiz]

Ups.. Forget to attach it

[Hugh_Compton]

Would you minf posting the scene file? Thanks

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Sorry for not getting back sooner, it's been a very busy weekend.

 

I just did a test with your scene... the intensity of your area omni (not sphere) was set to 0, so it had no effect on the caustics.

 

You're right, it's was omni, i did so many variants to get anything, i've forgotten what i uploaded.

 

I tried what you suggest here:

 

Turn of shadows, disable "affact diffuse" and "affact specular", and remember to set the light to generate caustics

And crank up the intensity!

 

And this is what i get

 

 

I just did a test with your scene... You can get the scene when I'm done

 

Tell me if you want the scene file and I can attach it...

 

Still not sure what i'm doing wrong, so, one big YES to both of your offers: please could you post either my scene with the changes you did, or the scene you did from scratch? Or both if you still have them, but your's looks much better so i wont complain if you post just that one.

 

Than you so much for the effort!

[Braiz]

hmm.. very weird

 

...

 

I see now... I will guide you through this, before I post the scene file.

Your omni light was set to "manual settings" under the "mental ray indirect illumination" group. That's why you explained that you used an energi setting of 500000 I think. NEVER use these options, okay, very important. Unless you have some serious out-of-this-world-need for doing so. Always use the automated options (which is the default).

 

Unfortunately I had already changed a couple of things in your scene file, so I couldn't recreate the render I did earlier from your scene file. So we will skip that part

So I'm only posting my own scene file. look at it, and perhaps compare with your own setup and settings, and see what works best for you. remember to check everything, lights geometry, caustic settings and so on.

 

Btw. That render I posted from my scene actually used 6.000.000 caustic photons, not 600.000 as I had stated earlier. Sorry about that. So because of that I decided to test it again to see if I had messed things up. Luckily, that wasn't the case

 

I have not used GI, only FG + caustic, I have not used maximum sampling radius, or anything else, Just kept these options unchecked. Plus I changed the settings of the water material. There are 2 bump maps in that material, so you can swith between them to see different caustic patterns, use them if you want. Plus i changed some things with the raytracing, but you can check and see if it actually has an impact on the render.

 

Try it out. You could do a new scene that works for you, and perhaps post the result in this thread.

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Your omni light was set to "manual settings" under the "mental ray indirect illumination" group.

 

Yes, in one tutorial i watched it was said that that way of doing things gives more control since the number of photons in general settings is divided on all the lights in the scene. Forgetting that tip right away :-)

 

 

You could do a new scene that works for you, and perhaps post the result in this thread.

 

Definitely, starting a new scene from scratch, we'll see how far i get :-))

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So here are the results, chronologically :-)

 

First i did everything to be as similar to your scene, including water plane with modifiers, an omni light, and 6500000 photons. Result:

 

 

Then i figured, what would happen if i put a rectangularly shaped spot light, point it downwards and assign half the photons. So here is what i get with that:

 

 

Next, instead of using a plane with all those modifiers on it, i created one big box for the water and assigned a water material from Autodesk Material Libray, again, with omni at 6500000:

 

 

and with spot at 3000000

 

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Then, a new solution for material is posted by kcpr raffaEl on this addres:

http://area.autodesk.com/forum/autodesk-3ds-max/lighting---rendering/caustics-through-mental-ray-in-max2012---pool-caustics-help-needed/page-last/

 

And here is the result with a simple plane, material pretty much the same as in my first scene with just that one change in it, and only 500000 photons, and photometric light (uniform diffuse generating from point):

 

 

As you can see the problem with this material settings (setting color with refraction max distance under advanced rendering options) is if you look under the surface everything is white.

So, to get under surface color, it must be set under refraction color in main material parameters:

 

 

 

All in all, once you get the rules you need to follow caustics aren't so difficult :-)

 

I would like once more to thank everyone, and offcourse, especially Braiz! Now it's time to put what i've learned in a real scene (indoor pool) which is how all of this got started :-)

[Braiz]

You're welcome dude...

 

It looks nice indeed..

You're getting the hang of it, although the renders do look a bit overexposed.

Regarding your water (the white water phenomena), you should try and increase the max distance in that material to see if that helps make the water more blue when viewed from beneth.

 

Actually, you don't need to use a box. You could use a plane instead, the result will be a bit different. It looks to me that you box is quite large/tall, which looks weird (that white transparent on the top part of the box).

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Regarding your water (the white water phenomena), you should try and increase the max distance in that material to see if that helps make the water more blue when viewed from beneth.

 

I did, but it works only when looking at the water from above. Once you get below surface, it's white. That's why i did that render where both situations are visible (honestly, how often does one needs underwater view :-) )

 

 

It looks to me that you box is quite large/tall, which looks weird (that white transparent on the top part of the box).

 

Actually the box in that render is "deeper" then the room itself. What looks like "white transparent" is different material (white one) on the whole lower part of the room. Probably why it looks overexposed.