Water caustics - fireflies

[synolog]

Hi,
i'm testing caustics using:

- corona sun+sky
- water with simple plane and material with reflection+refraction(caustic)+opacity+displacement+volume, cubic projection
- solids with a diffuse only material

- render engine bidir/vcm

I've noticed some fireflies that are connected with the kind of lightsource and material parameters. Are they phys correct?

Thanks

[cecofuli]

Try to add some glossy reflection to the water. I think that from 0.9 to 0.98 it's enough + a little bit of Bloom and Glare.

[synolog]

Thanks but problem still present. Best using PPM engine

[FrostKiwi]

In Bidir, there are certain high energy rays, that will never (in human years ;]  ) average out against the middle bright values of the scene.

Use the firefly denoise option, it will clear the fireflies and leave the scene intact.
Also, if water is a simple plane, then refraction is not correct. Water needs to be a volume.

[synolog]

Hi, thanks, but:
Bidir: denoise function doesnt have any effect (in firefly and full mode).
Volume vs plane: plane caustics seems to be more natural; with volume caustics are still the same in deep water and surface.

[FrostKiwi]

Bidir: denoise function doesnt have any effect (in firefly and full mode).

Ohhh, I just noticed, that we are in C4D >.>
Pretty sure it does in max.

No problem though, there is a workaround in post. You can even use a free tool. I posted about the exact same situation in another thread.

[synolog]

Thank you, i'll follow your instructions.

edit:solved thanks

[Lars Vader]

I never even once managed to see any kind of caustics in my renders. Would anyone of you be so kind and give me some tips on how to achieve them? I followed your path but no caustics what so ever. I tried water as a simple plane and as a box, used displacement, checked "caustics" in the refraction channel and checked volume as well, although I'm not quite sure what values I'm supposed to use.

[synolog]

I never even once managed to see any kind of caustics in my renders. Would anyone of you be so kind and give me some tips on how to achieve them? I followed your path but no caustics what so ever. I tried water as a simple plane and as a box, used displacement, checked "caustics" in the refraction channel and checked volume as well, although I'm not quite sure what values I'm supposed to use.

Hi, there are many ways to achieve caustics. Here an example:

1st-render settings: in performance settings enable devel/debug mode; in develpment/experimental stuff under basic configuration in render engine select Bidir/VCM.

2nd-model a swimming pool and assign a corona material with diffuse white 80%.

3rd-insert a plane for water surface: for it use a material with no diffuse; activate reflection; activate refraction; activate opacity with brightness 50%; activate displacement with c4d_water shader in texture; activate volume with color 5% cyan and absorption distance 5cm (or more depending of the plane water surface size), volume scattering deep blue color, brightness 25%, mix mode add, mix strength 50%.

4th-standard corona sky and corona sun, insert corona camera with exposure -3(EV).

I wish this will help you.

[RolandB]

1st-render settings: in performance settings enable devel/debug mode; in develpment/experimental stuff under basic configuration in render engine select Bidir/VCM.

Hi synolog
Thanks for your answer but (I'm on Max and with the 1.5), I've no devel/debug mode in performance settings. So without Bidir/VCM, is it possible to produce caustics (i don't think so, I've tried...)
Thanks
Roland

[synolog]

In Cinema 4d you need Bidir/VCM or PPM. I dont know if the progressive mode in Corona for max 1.6 supports caustics and how to activate Bidir/VCM in Corona for Max 1.5. Maybe you could find more info in the Corona/Max forum.

[Lars Vader]

I never even once managed to see any kind of caustics in my renders. Would anyone of you be so kind and give me some tips on how to achieve them? I followed your path but no caustics what so ever. I tried water as a simple plane and as a box, used displacement, checked "caustics" in the refraction channel and checked volume as well, although I'm not quite sure what values I'm supposed to use.

Hi, there are many ways to achieve caustics. Here an example:

1st-render settings: in performance settings enable devel/debug mode; in develpment/experimental stuff under basic configuration in render engine select Bidir/VCM.

2nd-model a swimming pool and assign a corona material with diffuse white 80%.

3rd-insert a plane for water surface: for it use a material with no diffuse; activate reflection; activate refraction; activate opacity with brightness 50%; activate displacement with c4d_water shader in texture; activate volume with color 5% cyan and absorption distance 5cm (or more depending of the plane water surface size), volume scattering deep blue color, brightness 25%, mix mode add, mix strength 50%.

4th-standard corona sky and corona sun, insert corona camera with exposure -3(EV).

I wish this will help you.

Thank you, synolog!
I did everything you mentioned but still no result. It must be jinxed, I don't know. Seems so easy and yet it doesn't work.

Btw: Could you also tell us how you solved the firefly problem? I'd really like to know that once I figure out the damn caustics. :-D   

[synolog]

I forgot the most important setting: in the refraction settings of the water material turn on (under refraction behavior) Caustic (slow). If it doent work send me your c4d file.
For fireflies look this https://forum.corona-renderer.com/index.php/topic,12284.msg89798.html#msg89798

[Lars Vader]

I forgot the most important setting: in the refraction settings of the water material turn on (under refraction behavior) Caustic (slow). If it doent work send me your c4d file.
For fireflies look this https://forum.corona-renderer.com/index.php/topic,12284.msg89798.html#msg89798

Sent you a PM. Still nothing. Curious to find out what my mistake was.

[synolog]

Hi,

the problem in your file is the volume parameters of the water material:

In absorption color HSV parameters put H200 S2% V100%; Absorption brightness 100%; Absorption distance 8cm (if you increase this water is more transparent).

In scattering color HSV put H230, S100%, V15%.

Your file is from c4d R15 and if i save it with my R18 you cant open it.

Let me know if you solve

[Lars Vader]

Hi,

the problem in your file is the volume parameters of the water material:

In absorption color HSV parameters put H200 S2% V100%; Absorption brightness 100%; Absorption distance 8cm (if you increase this water is more transparent).

In scattering color HSV put H230, S100%, V15%.

Your file is from c4d R15 and if i save it with my R18 you cant open it.

Let me know if you solve

Thank you so much. It finally worked! :-)

[Cinemike]

Your file is from c4d R15 and if i save it with my R18 you cant open it.

As a sidenote: R15 can open R18-files.

[synolog]

Your file is from c4d R15 and if i save it with my R18 you cant open it.

As a sidenote: R15 can open R18-files.

Sorry my mistake.

[Cinemike]

The "may not" portion of the message is mostly referring to advanced features of higher versions (so the Voronoi Fracture from R18 cannot be used when loaded into R15, for example). The file format is basically fully compatible. So, if you press "OK", the file will be saved for R18, but as long as you do not add advanced features, it will remain backwards compatible.

[Air Dnipro]

Hi synolog!
Can you send me plz your c4d-file with caustic? Whatever I do stil I have no caustic (cant get caustic effect)  ;(

[maru]

Check out this guide: https://coronarenderer.freshdesk.com/support/solutions/articles/12000043584
It's for 3ds Max but should be easy to understand for C4D users as well.

[Konichowaa]

I'm having trouble as well creating caustics,

I also can't find the develoment mode to begin with, in beta 1...

[maru]

Edit > Preferences > Corona > Enable devel/debug mode
Then you'll find it in Render Settings > Corona > Development/experimental stuff

[Beanzvision]

Here's a test scene for those wanting to play around. Note: you will need to download the hdri used. (See txt file in zip)

[Air Dnipro]

Its looks a pretty cool! I try download it and rendering, whatever happend - thank you!

[Air Dnipro]

I try rendering this scene, but stiil have no caustic )
here is my rendering:

[Beanzvision]

I try rendering this scene, but stiil have no caustic )
here is my rendering:

Do you have developer/debug mode turned on? *See maru's comment.

[Air Dnipro]

Yes, I turn on debug mode. I try PPA and Bidir/VCM render engine... Very slow rendering, now I have 30 min, maybe later been a caustic effects in render window )

[Air Dnipro]

Wonderful, now I try to PPM render engine, and...OMG I see a caustic! ) Its amazing! THANKS to you, amigo!!

[Eddoron]

Caustics require a big enough light to be correctly sampled. The HDRI or the Sun/Sky Object won't help much. Also, the PPM engine will fuck many of your other materials. Try using a huge circular Area light directed at the pool with directionality ~60.
It's best to only have the top part of the mesh be displaced and not ripped off from the rest of the box. Also, a portal might help.

[Air Dnipro]

Caustics require a big enough light to be correctly sampled. The HDRI or the Sun/Sky Object won't help much. Also, the PPM engine will fuck many of your other materials. Try using a huge circular Area light directed at the pool with directionality ~60.
It's best to only have the top part of the mesh be displaced and not ripped off from the rest of the box. Also, a portal might help.

This engine metod good only gor caustic effect? maybe I can merge my pool with other scene? As I know Corona have no caustic mask in multipass (   Thanks for advise, its very helpfull

[Eddoron]

or just fake the caustics. nobody will ever try to recalculate the rays back to their origin. maybe a savant, but those are rare.

[Air Dnipro]

as I can see caustic effect need much light, how to increase caustic that on wall (near pool) I see caustic too?

[Beanzvision]

as I can see caustic effect need much light, how to increase caustic that on wall (near pool) I see caustic too?

Try using a c4d light and project a caustics map on the wall.

[Air Dnipro]

You mean using c4d-light in corona-scene? I dont know how to separate caustic by multipass )

[Beanzvision]

Fake it til you make it.

[Air Dnipro]

its so realistic caustic! looks very realistic and cool! caustic on the wall made by corona?

[Beanzvision]

The wall caustics was generated by a c4d spotlight with just a c4d alpha mat applied to the light and projected in flat mapping. For a 2 minute setup, i wouldn't call it realistic but if one spends more time on something it could be better. ;)

[Air Dnipro]

hmm, how do made alpha-channel in standart renderer of Cinema 4D? ) I try to use standart c4d-light in corona (PPM render engine) and render was worse )

[Eddoron]

You have to align the texture to the (spot)light first.
And get away from the PPM engine. It won't help you a bit when you're faking it anyway and the rest looks often worse.
You could also use a noise in the illumination /opacity channel, stacked onto the material that you want to have the caustics. One or two animated noises and maybe a distorter should be enough.

[Air Dnipro]

Thanks to you, amigo!

[Air Dnipro]

I find interesting c4d-file with caustics, maybe it help someone ;)

[Eddoron]

I added a spotlight with a distorted noise, so you can have animated caustics and control where they appear.

[Air Dnipro]

I create real caustic in cinema 4d, but look like a fake... And I have a some artifacts in shadow

[Marvey]

Fake it til you make it.

can you share the scene? thanks

[Air Dnipro]

This caustics is merge with corona-scene? I increase surface caustic in Light, and I get this fake-render:

[Beanzvision]

Fake it til you make it.

can you share the scene? thanks

Sure!

[Air Dnipro]

Thank you so much, friend! Your scene look much more better then standart-render cinema scene`s! Looks a physically correct

[Marvey]

Fake it til you make it.

can you share the scene? thanks

Sure!

thank you! ;)

[Marvey]

Beanzvision, it is possible to update it with the new caustics? thanks!

[Air Dnipro]

Corona Beta licensing is over ;(

[Beanzvision]

Beanzvision, it is possible to update it with the new caustics? thanks!

Not really much to update here, remove any C4D lights that were projecting fake caustics, ensure caustics is enabled on the material and also in the render settings. That should be it, if you run into an issues let me know and I'll do my best to help you with it.

[synolog]

Finally great results with the latest version

[Beanzvision]

Finally great results with the latest version

Looking good too! ;)

[Air Dnipro]

Looks pretty cool! unfortunately beta version licensing is no more ((

[TomG]

Looks pretty cool! unfortunately beta version licensing is no more ((

Even if there was beta licensing, since this is a daily build, it still would only be available for those with an active FairSaaS license :)

[Air Dnipro]

You are lucky man, and I have no this license (