OTOY Forums

Hi everyone,

I am kinda new in here, but I hope you can help me.

I am running on the 3D Studio Max Plugin, and I am trying to get some proper caustics. I read to get caustics we have to use PMC, one light emitter, but still, i can't get any caustics in my render and i don't see why. Please enlight me.

Here is my test scene with just a shadow from the glass. i read somewhere to uncheck "fake shadow" right?


and here are my settings for kernel and material:


Some thoughts?

Hi,
Firstly you need to activate the "fake shadow" option, than you need a tiny light source to reduce the blurriness.
Then, in the kernel settings, reduce the Parallelism to 1 and rise back the GI Clamp (this parameter cuts the coustics).
I hope to have not forget anything
ciao beppe

Thanks for the reply. This is what I get with your setting:

For the record, my system unit scale is: 1unit fo 1 millimeters
I know there are some trouble if you use the wrong unit scale, so I also try 1 unit for 1 meters, and it doesn't look better.

mmm, the shadows seem still way too soft, there is surely an issue with the scale
How big is your light source?
Please, try this, disable the emitter and use the physical sky, you should see a big difference in terms of shadow and coustic sharpness.
ciao beppe

It looks to works with a day light:


Thanks!
But I am not a huge fan of the octane day light, I had a better control and a better look with the octane light. You guys always use daylight for caustics render?

Welcome to terold!

You're interested caustics. And I also!

What's your videocard?

If you're interested REAL-LIFE, then you should:
--> glass material
- disable "fake_shadows"
- enable dispersion 0.005* -> therefore, ior original 1.500 -> change to 1.483** ior dispersed

--> PMC settings
- set maxdepth 16 (both diffuse and specular)
- parallelism 1 for appear caustics earlier
- keep to disable "caustic blur"
- change to max GI clamp
- if your great area of light emission then change to ~8,000 samples per pixel (spp) or if it's sun on earth then set 100,000~150,000-spp at 1002x602 (resolution screen)


* -> formula of dispersion conversion: (n_d - 1)/v_d*((0.48613^2*0.65627^2)/(0.65627^2 - 0.48613^2)) = dispersion coefficient
n_d - it's ior
v_d - it's abbe number

** -> formula: ior_orig - 10/3*coef_disper = ior_disper

IMPORTANT: Any specular material ALWAYS has dispersion at real-life.

If you've any doubt then you can contact me.

terold wrote:It looks to works with a day light:

Thanks!
But I am not a huge fan of the octane day light, I had a better control and a better look with the octane light. You guys always use daylight for caustics render?

Hi,
as I told you, there is a problem with your scale settings, the physical sun is like an infinite point light so you should have coustics even if the scale is wrong. In theory, with a correct scale, you should obtain almost the same effect with an emitter of 1 or 2 cm
ciao beppe

Thanks nuno, i go to try your settings right away!
and about my videocard, it is a geforce GTX760.

It works really fine. Acutally, I had to use IES light for a better render and caustics works.