C4D - How to use Redshift Caustics! (Quick Start)

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How to use caustics while rendering in Redshift
In order to add caustics to your scene you need at least one object to cast caustics, one to reflect them and a light to emit caustic photons.
** Also, make sure bucket rendering mode is on in the render view or you won't be able to see any caustics **
Select the object you'd like to emit caustics from and the objects that will reflect those caustics.
Add a Redshift Object Tag to each of them.
Click the RS object tag for the object that will cast caustics - Select the Visibility Tab - check the override option - In the bottom right under the global illumination parameters select the "Cast Caustic Photons" box
Click the RS object tag for the object that will reflect caustics -Select the Visibility Tab - check the override option - The "Receives Caustic Photons" option will be on by default.
Select the lights in your scene that you would like to affect the caustics - go to the Photon tab and under the Caustic parameters select the "Emit Caustic Photons" check box.
Increase the "Number of Photons to Emit" parameter a lot... like a lot a lot. The default value is 100,000 - you probably won't get decent results until your over 10,000,000 photons.
Open up the Redshift Render Settings and make sure the "advanced settings are turned on". Deselect automatic sampling and adjust your samples min and max to be more appropriate for your scene. My default is usually min 4, max 512. Select the reflection, refraction and light overrides increase each of these to 2048 to give those areas of your render more samples to work with.
Turn on the picture viewer and see how your caustics are looking. You can also preview them in the redshift render view with bucket mode on as I mentioned earlier but I want to see our render in full resolution.
If you're already using a large # of photons like I suggested but you're seeing a lot of tiny dots making up your caustics, you can go to your RS render settings, select the Caustics tab, and increase the blur radius. Move it upwards in small increments until your caustics appear smooth. If you increase it too much you're caustics will begin to blur and lose their detail.
You can always go back to the "number of photons to emit" parameter in your light and increase it even more to get better quality caustics but this will continue to increase your render times.
As you can see adding more photons and adding a small amount of blur radius to our settings really helped clean up the render.
Lastly you can also increase the "intensity multiplier" to brighten your caustics. This won't make the quality of the caustics better in any way, it will only make them brighter which is sometimes helpful when your balancing the levels of your lighting throughout your scene.

[@michaelkonomos]

Man, having the tip you gave about bucket render turned on or it won't render just helped me out of a jam. thanks!

[@taylor-kenny]

I had the same problem first time I tried caustics!

[@Birii23]

Exactly what I needed and straight to the point! Thank you!!!!

[@blinn40x]

excellent tutorial & great format, thanks!

[@Jayrust]

quick, clear, concise tutorial. Loved it. thx. subscribed!

[@the-astropath]

Thank you! That's my goal, more on the way.

[@beMOTIONdESIGN]

Subscribed and bookmarked! I'm gonna have to come back to this after I learn more of the basics of Redshift.

[@the-astropath]

Thank you! More to come, I really want to be more active on the channel this year.

[@beMOTIONdESIGN]

@@the-astropath I totally hear ya! Now that I don't have the stress of freelance, I'm making plans to get cracking again with my channel. Let me know if there's anything I can do to help!

[@harrisonbruhn8528]

Thanks again man! Incredible!

[@BentleyRobles]

This is so cool! I was wondering what you like like though. Would you be able to put yourself in it? In a small box or something?

[@scheerlon]

nice, since i dont use caustics every day, this is great to come back if I forgot something. Really nice breakdown in such a short time with no useless whaffle as intro :) sub my friend. also love the time this got recorded, so I am not the only one working at night ;)

[@the-astropath]

haha! I focus best late at night I find. Glad you liked the tutorial, more to come.

[@atruefreethinker1944]

quick and to the point. thank you.

[@the-astropath]

Thanks! Appreciate it :)

[@SansFamille]

very helpful tut, thnk you a lot =)

[@Brandonbraun]

so easy thanks man!

[@blacksmoketv2023]

I followed the steps but my scene is almost completly white.. what could it be? My water, walls and main light have the appropiate RS tags and bucket rendering is on

[@the-astropath]

I'm not sure, it's hard to diagnose without seeing the scene. What kind of light are you using for your scene?

[@AshleyGlover]

On the latest RS it is now under the Details Tab at the bottom.

[@malek7396]

Great 👍👍👍👍

[@loganpenciu7317]

Thank you so much for sharing! Is there anyway to get caustics to work with a VDB light source? In my case I have an oil lamp with a VDB flame inside. I would like the flame to generate the caustics through the glass of the oil lamp. But I feel like the answer is to put a point light inside of the VDB to match positions, and use the Redshift tags to only have the light affect the glass of the lamp and emit the caustics. Is that a correct assessment?

[@the-astropath]

Glad you liked it! I believe your assessment is correct. As far as I know you can't get caustics from a VDB emission. I wonder if you could put an animated texture in an area light to simulate the flickering? I haven't tested that.

[@loganpenciu7317]

@@the-astropath Thank you for the insight!😃

[@fabriziotorchia8376]

Beautiful tutorial. I recently switched to redshift, but caustic photons doesn't work !! Do you by any chance know the reason for this problem? I have a 2080 rtx and I have updated all the drivers, but nothing.

[@NotTheLarryDavid]

Make sure you have the tags in place to override the caustics behavior on the objects. Also make sure your lights are emitting photons. Lastly, go to your RS settings and make sure Caustics are turned on.

[@ryangame9515]

Thanks for the tut mate. Just an FYI youre doing global sampling all wrong. Max 512 is almost never necessary. You should keep it much much lower, and increase samples on a per light and per material basis.

[@the-astropath]

Hey Ryan, do you have some documentation on that? I've personally never seen it approached that way. Happy to check it out.