Corona Version 4 - Caustics Help Please

[MilkmanDave]

This new video by the Corona Team showing CAUSTICS reflective from the Chrome Wheel is great, I need a tutorial or quick explanation to achieve this result.  Please this youtube video at :35 seconds.       

  Thanks for any guidance.  Cinema 4d only.  I do NOT use 3dsmax.  My scene is attached - I'm failing to get the right result.

[houska]

Hi MilkmanDave!

Try to render with caustics enabled and disabled in Corona Light and compare those two images. You'll see that the caustics are indeed there. There are however two issues with your setup:

1.) The light emitter is so big that the caustics are everywhere and you have a hard time seeing them.
2.) The geometry is not so well-suited to show-off caustics. What you want is concave surfaces that will focus light, making the caustics very bright in some places of the image

[MilkmanDave]

Thanks Houska!  I'm attaching my scene again.  I'm actually getting some better results with your help.  I made the lights smaller and cranked up the power from 50 - to 200.  I added a wheel with concave curves.

Thank you - looking better. ☺  Let me know if you have more suggestions.

[mb3d]

Hello.
You have to exclude the object & the floor so caustics can work/show.

I've put a example file so you can check this :)

[houska]

You have to exclude the object & the floor so caustics can work/show.

Sorry, but no. What you're doing there is a hack. The fact that caustics work with excluded objects is a mistake. Normally you'd want to have one light for both lighting the scene and for generating caustics. Separating these two doesn't make physical sense and is terribly wrong. :-)

[mb3d]

I didn't say it was the correct way to do it. This is just a workaround until it is possible with one light, like you said.

[houska]

It's possible now, you just have to make the light smaller :-) Try to make caustics visible with a huge softbox in real life and it will also be harder. Plus the object in MilkmanDave's scene is not too well-suited for caustics.

[Beanzvision]

Working to scale always helps things look better. I noticed that the IOR value for the metal is way too low for reflective caustics. We recommend a min value of 10. I scaled the scene down, the lights were reduced in size and power, all excludes were removed and the IOR was increased.

[MilkmanDave]

Thank you EVERYONE.  Thank you also to Bengamin at Corona.  Got it all figured out.  Case closed.