Mnteal - ray - problems with caustics.

[Environment]

Hey.

 

I`m currently learning mental ray. I work on caustics.

 

I have a problem. When I turn caustics off, I see normal shadows.

When I turn it on, the shadows are completely black, no matter how much photons I set.

 

What`s the problem? I use 3ds max 2015 demo version.

 

It looks like that.

 

Caustics OFF

 

 

Caustics ON

 

 

 

[Zdravko Barisic]

To be honest, if you learn MR, and you here on CGArchitect, caustic is the last thing you should learn.

I know so much people in Archiviz, and I can not rembember that anybody, anytime, anywhere...used caustics, in any render.

Except faking caustics, ofcourse.

You should learn a lot of much more usefull stuffs, like HDRI, interior lighting, etc...

I hope I helped you in someway...

Good luck!

[Environment]

Thanks for answer, but I know I need caustics. Maybe it`s true here on CGarchitect not many people will know it.

 

I mean I need to figure out how to do it in mental ray.

[Zdravko Barisic]

OK, I bumped your thread, at least!

I hope someone will answer to you soon.

Good luck!

[Francisco Penaloza]

Can you explain a little more about your scene setup.

in a nutshell, you need a light that can produce caustics, for example MR sun, then right click on the sun and be sure produce caustic is active, then you need to do the same for the objects that you want to cast caustics.

Also check for the glass material, thin glass or double face glass.

Activate caustics on the GI section of the render panel and it should work fine, also your shadows should be Ray traced.

[Environment]

Thank you for help Francisco.

 

I use everything as you said, I only use photometric light and arch & design physical glass, is it ok?

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What`s the problem? I use 3ds max 2015 demo version.

 

Getting caustics to work can be tricky, but once you know all the "rules" there should be no problem.

 

Render settings

- experiment with max number of photons per sample (lower for sharper caustics)

- manualy set low maximum sampling radius (experiment, for sharper caustics go lower)

- set filter to cone

- turn on opaque shadows

 

Object properties

- select objects you want to generate caustics and on mental ray tab turn on generate caustics

 

Lights

- first set your lighting without caustics

- then create a spotlight that will be used just for caustics, concentrate it's cone just on objects that are to generate caustics

- turn off shadows for that light

- emit light from point

- turn off diffuse and specular

- turn off automatically calculate energy and photons

- turn on manual settins

- set it's GI photons to zero

- experiment with energy and number of photons (these go really high, millions)

- open object properties for that light, also turn on generate caustics

 

Materials

- for glass, start with physical glass preset, don't use others

- then play with settings in advanced rendering options rollout to get the look you want (max distance and color of refraction)

 

Result and scene:

 

Caustics.zip

[Environment]

Hey Dario.

 

Thank you a lot for a detailed help.

 

I found a reason why my caustics didn`t work. I created geometry of size around 400cm ( 4 meters ) and I sticked to setting from a tutorial were objects were around 20cm high. I think it was the setting "Maximum sampling radius" which was too small for such a large objects.

 

Anyway it looks like that now. Caustics are ok. I only wonder why shadows are black. I mean I understand that glass is not 100% tranlucent, but still I don`t think they should be black.

 

[blank...]

I only wonder why shadows are black.

 

Share your scene.