Caustics being calculated when turned off?

Corona Corona for 3ds Max Help Required
1

Is it possible that subtle caustics calculations are happening even when it’s turned off (reflective caustics)

See attached.

Sunlight (HDRI in Corona Bitmap) pointing at a pool, the fireflies are where I’d expect reflective caustics to be if they were turned on. The only issue is, caustics are turned off in both the render setup and the water material. The ‘clay’ material has reflection set to 0. The pool has a water shader on it so is both reflective and transparent.

If I put a basic material on the water geometry, those fireflies don’t appear. If I turn the reflection down to 0 in the water material but leave refraction at 1, they also disappear. Which is making me thing it’s a caustic thing?

CAUSTICS.JPG
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2

Reflective caustics are always calculated, as mentioned on the caustics helpdesk page at https://coronarenderer.freshdesk.com/support/solutions/articles/12000056738-how-to-render-caustics-with-the-new-caustics-solver- “Note: reflective caustics are always calculated, regardless of the state of the material’s caustics checkbox.” - they are usually just too faint to notice.

You might want to try turning the new caustics solver on (remember, reflective caustics are always calculated, just with the old solver if the new one isn’t on), as it might be faster and/or cleaner. Or you might want to use the Rayswitch on the pool material to turn off how it reacts to GI so that it doesn’t reflect anything.

3

Thanks Tom, glad I’m not going insane

4

And this article explains even better what is happening and why, and how to disable caustics completely: https://coronarenderer.freshdesk.com/support/solutions/articles/12000066318

5

Thanks Maru

I don’t need to turn them off I just wondered what it was. Now I know.