Caustics - Fireflies - again

Corona Corona for 3ds Max Help Required
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That’s what I’ve ended up having to do, rendered the image twice once with and once without caustics.

The downside to this is that the devs say Caustics don’t work with regions, so you have to render the full res image. The full res image is 5000 pixels and with caustics turned on it takes 8x longer to render than without

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This type response is exactly what I was referring to in another thread (the one about DR/RAM), whenever I have an issue the ‘solutions’ always seem to result in a ‘downgrade’ so to speak.

  • I am afraid this is the best response I can currently deliver.

My goal is to create the absolute best images I’m capable of, I select my software based on whichever one allows me to achieve that. If a company tells me they have a ‘1 click caustic’ solution I’d expect at the very least for a 1 click caustic solution, not a 1 click caustic solution providing you do X and Y which will result in a worse image than the one you started with.

  • I agree that the “1 click” does not apply to all kinds of scenes. If the complexity is too high, the render time needed to get reasonable image quality will grow. But still, in many cases the “1 click” is relevant, and we always did explain that additional render time will be needed. Isn’t it the same with many other features? (think of refraction, SSS, volumetric fog, displacement - if you throw too much at the renderer, it will need more resources to finish the job)

I thought Corona had a heavy focus on allowing us to achieve physically correct photorealistic results and that you weren’t about ‘fakes’ etc.

  • Correct. The fakes here are to get as fast rendering as possible and as good quality as possible at the cost of some realism, which should be hard to spot anyway. I don’t think it’s something uncommon though.

With that in mind, to answer your first question, no, i don’t need those reflective caustics because they don’t look particularly great but unfortunately they’re not optional, but I absolutely need my materials to look as good/realistic as they possibly can.

  • As explained in my post, you can disable them using the rayswitch map while keeping the water’s refractive caustics enabled.

Querying whether I need reflections on my materials seems like such an odd thing in a world where we’re striving to achieve CGI’s that are as realistic as possible and pushing the boundaries with PBR etc. If I didn’t need reflections etc I may as well just jump back to 1986 and whip out my crayons.
Out of interest do you have a list of real world materials that don’t have reflections?

  • Sure. It is again a matter of “realism vs performance” and how much you are willing to sacrifice. That’s why I asked if you need those reflections, rather than ordered to disable them to get reasonable performance.

Also just +1 everything Alex said, I missed his messages before typing mine out.
I think the biggest disappointment for me was this was the one scenario where I thought caustics would shine as it’s the one used in all the demos/tutorials/sample scenes/documentation whatever. It’s the most basic caustic setup really. 1 direct light, 1 refractive object. Doesn’t get any simpler in terms of scene setup - obviously I can’t comment on the technical aspect

  • I understand this. Please just note that it’s not the number of lights or objects that decides about the caustics quality/speed. I can easily imagine a scene with just 1 object and 1 light which would produce persistent noise with caustics. It is more about the overall complexity of the scene.

And again, just to avoid any misunderstandings - I am not arguing with you, just explaining how things work and trying to provide as much help as possible. We are aware of various issues with the caustics solver, and we have them logged with good examples so that our developers can improve it in the future.

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No problem Maru - thanks for the assistance on this and your work looking for solutions. It’s appreciated even if I don’t sound like it is :smiley: