Problem with caustics not coming out as expected.

[Alex_M]

I'm trying to use caustics to achieve a specific effect with a crystal ball but they don't come out as I expect. I want to achieve this effect:



But I'm getting this:



I'm not seeing the hotspot in the center behind the ball and the dark shadows as it should happen in reality. My Vray settings are at their defaults except these:

Probabilistic lights "off"
Caustics "on", search dist 50 cm, max photons 1000, multiplier 20 (for stronger effect without increasing the strength of the light source)
Override depth 25, max ray intensity turned off (for full dynamic range)
The caustics subdivisions of the light object are raised from 1500 to 2500.

The glass material is reflect & refract 255 white, affect shadows "on", reflect on back side "on"


Maybe I'm missing something?
Please see attached below the scene.

Thanks in advance!

[Alex_M]

Ok, I found the problem! For caustics to work, one should also disable "Affect shadows" in the glass material. I don't see this mentioned anywhere in the help page for the caustics effect or the VrayMtl. Maybe it will be good this to be mentioned there to avoid such confusions?

By the way, what does the "Direct visualization" option do? There's no description about this in the help pages. In Max if I hold the mouse the description balloon says that it shows the calculation of the caustics but I found that it also introduces noise that won't go away no matter how long you leave the render running. Can someone clarify about this and when and if we should use this option?

[svetlozar.draganov]

Glad you've found the reason by yourself.
This has been mentioned on several placed on the forums but I don't see a note about it in the Documentation so I'll add a new task about it.

[Alex_M]

Thanks. And what about Direct Visualization? When should we use it and what is its purpose?

[svetlozar.draganov]

It is a preview of the caustics calculation, similar to Irradiance Map and Light Cache calculation preview.

[Alex_M]

Aha, got it. Thanks!