free experimental scene with caustics in corona4

[evalery]

Hi guys,
did some experiments to test caustics with Corona4 for 3ds max and got lots of fireflies. After many hours of rendering but on a relatively old machine - on an i7 -4770K CPU @ 3.50GHz, AMD graphics... tried rendering these crazy comps on 4k resolution and on 2k in to see what happens. Even at under 2% noise the fireflies were still there.

I posted this here and on corona group on fb and Thomas M. Grimes gave me the idea to share the scene here for everybody to take a look or play with it and give some feedback or notice problems or whatever. quote: "If all else fails, you can post over on the forums and share the scene with us for devs and support to take a look " - so please find attached the maxfile (made in 2018 but saved in 2016) version and the HDRI is here - 08-08_Sunset_E

http://noemotionhdrs.net/hdrevening.html

Thanks!

[maru]

One question: most of the materials (all?) in this scene have refractive caustics disabled. They should be enabled first, before any optimizations, am I right?
One more: which frame of the animation should be rendered?

[evalery]

One question: most of the materials (all?) in this scene have refractive caustics disabled. They should be enabled first, before any optimizations, am I right?
One more: which frame of the animation should be rendered?

Thanks Maru, I thought that if it's enabled is going to slow rendering so much more, I had no idea that actually it affects everything. I thought if you enable caustics in the performance tab somehow overwrites that... but that's not right, isn't it?

[maru]

Enabling the checkbox in render setup will enable the new caustics solver, which will always render reflective caustics and will render refractive caustics if they are enabled in the material.
If caustics checkbox in render settings is enabled, and caustics are disabled in a material, then that material will not cast refractive caustics (it will use simple transparent shadows instead).
If caustics checkbox in render settings is disabled, and caustics are enabled in a material, then that material will cast refractive caustics, but they will be rendered using the classic path tracing solver (slower, worse quality).
More info here: https://corona-renderer.com/blog/corona-renderer-4-for-3ds-max-released/

[evalery]

Enabling the checkbox in render setup will enable the new caustics solver, which will always render reflective caustics and will render refractive caustics if they are enabled in the material.

Thanks for your answer. I'm gonna rerender it to see if this was causing the fireflies but it will probably take ages.

Thanks,

[maru]

I checked the scene again, and here are my conclusions:
- The scene itself is designed in a way that is hard to render for our caustics solver (at least at its current stage of development). I can understand that users may want to render similar scenes, so I will report it to our dev team for further investigation (Is there some instant fix in the scene itself? Should we improve the solver? ...)
- I tried rendering the scene for 15 minutes at a lower resolution (~1024px), and I did not manage to get acceptable quality, even after heavily adjusting render settings.
- Here are some things that can be done to "fix" the scene and lower rendering time:
   - Simplify the materials - for example, usually there is no need to use triplanar map and bump maps in every liquid material
   - The background / ground material should not have any advanced properties like reflectivity or refraction (if possible, of course)
   - Caustics should be enabled only for the materials which really need them
   - Corona Light can be used instead of Corona Sun (sunlight is very sharp and intensive)

Other than that, I understand that this scene can be seen as a kind of benchmark for Corona caustics, but in this case I don't think there is a way to render them to a good quality other than just letting them bake for a really long time.
I used Corona 4 HF1 on an i7 6700.

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[evalery]

Hi Maru,

Thank you so much for looking into this scene and thanks for all your comments. I actually tried again now in a different scene - with simplified materials and also I ticked the box with caustics in the material slot as well (not only in the performance tab). The main glass material I used this time is the builtin corona material for glass only with caustics on. Also I only have an hdri and a sun. If you think it would be useful, I can also share this scene as it is just a test scene.

The effect looks better now but I still got fireflies as you can see. Attached is the image directly from the frame buffer and another one with the caustics pass overlayed in photoshop (actually with linear dodge) and some retouching. The render had 125 passes and the noise level was almost down to 1.09%

I can understand that users may want to render similar scenes, so I will report it to our dev team for further investigation
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- Thank you for this! I must say - love experimenting and I like to try things that can be absurd, abstract, awkward, etc. To tell you the truth, I looked a lot at some guys that create abstract compositions in Cinema4D and Octane... guys like Peter Tarka, Roman Bratschi, Philip Lück, etc... their work inspired me to try to see if I can do "similar" things with max and Corona...
I do love to also create stuff that goes beyond visualisation, beyond just "let's imitate reality" - in which corona already does a great job. I worked in archvis and really I had amazing results with Corona since 2015, but I'm also a graphic designer and do a different kind of work. I'm also into branding and marketing imaging, love to try 3d for advertising, branding and illustration, I like to play with particles and massFX and to try new stuff, I still have lots to explore even in 3dsmax... and maybe even go into motion (tried already a small animation with corona) so... the sky is the limit...

thanks so much
cheers,
V

[evalery]

ok, so this is the raw render (for the previous post)
thank you

[maru]

I worked in archvis and really I had amazing results with Corona since 2015, but I'm also a graphic designer and do a different kind of work. I'm also into branding and marketing imaging, love to try 3d for advertising, branding and illustration, I like to play with particles and massFX and to try new stuff, I still have lots to explore even in 3dsmax... and maybe even go into motion (tried already a small animation with corona) so... the sky is the limit...

That's great! We (speaking for the whole Corona team) enjoy seeing amazing photorealistic archviz shots, but abstract/surreal works are often even more inspiring. It is perfectly fine to post all kinds of works in our gallery, and to ask any kinds of questions.

About the new scene - as usual, could you send it? :)
https://corona-renderer.com/upload

Generally I try to stay away from development settings, but here is something I think might help in your case:
- Enable devel/debug settings - https://coronarenderer.freshdesk.com/support/solutions/articles/12000021288
- Go to the Performance tab, make sure you have the caustics solver enabled, and you will see a new rollout called "Caustics solver settings"
- Increase "Max photons/iteration" from the default 5 000 to a higher number. I would recommend trying with 15 000 for the beginning, but you can try with much more, even up to 50 000. Just please note that this can slow down the rendering of the non-caustics part of the scene, and may greatly increase RAM usage, so in worst case you may even get a crash.

Another idea would be to try the newest daily build, which already has some caustics improvements implemented:
https://coronarenderer.freshdesk.com/support/solutions/articles/5000570015

[evalery]

Thanks a lot! just installed the latest daily build so I'll do more experiments :)

Thanks so much Corona team for the great support

[evalery]

hi, i did another test on the same scene with the daily built. As you told me, I increased  "Max photons/iteration" from the default 5 000 to 15 000.
tried to upload the scene on the link you shared but it didn't want to upload, maybe it's my internet or smth i don't know.

here's the scene anyway:
https://drive.google.com/drive/folders/110DX3D1F1QtrCuiUZurDZMYFBkWxnqKQ?usp=sharing

I attach the stats but you can find everything in the folder. This scene is a bit over the top anyway but i just wanted to kind of "push it" just for test. It's highly unlikely to have such a scene for a client but this is just a play.

many thanks,
cheers

[evalery]

so i tried again to render the scene with the glass (from the beginning of the thread) with some changes of materials and lighting, i mean simplifying it and i had a funny error (attached)

[TomG]

As the message says, please send us the scene - the info to include, and the link to the private uploader, is on https://coronarenderer.freshdesk.com/support/solutions/articles/5000524006-how-to-report-issues-3ds-max. Thanks!

[evalery]

yeah, thanks, I did. I tried before and it just didn't upload it, now i hope it is

[rowmanns]

Hi,

Thanks I have the scene, we will investigate this.

Cheers,

Rowan

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