Splotchy / noisy caustics

[Andrew_G]

Hi,

I use KS11.2 and I try to render very simple scene that includes some caustics. But no matter what I do, I always get very splotchy results. I tried to use HDRI, I tried to use Spot light. I tried on Product and Interior modes ... result was always the same. Usually I render on GPU, but I tried to use Custom Controls on CPU to make results cleaner - but this still didnt work.

Below is an rendered region with insane sample volumes: 13000. Still splotchy...

I`m also attaching scene itself - if some of you might explain what is happening here that would be great.

[RRIS]

Your caustics are blurred because of the diameter of your spotlight. Reduce this diameter and your caustics will start to get crispier. Regardless of that, you will still need a lot of samples.

Attached image is at roughly 500 samples.

[Andrew_G]

Hi RRIS,

Thanks for your reply, but it's not the issue. I know that I had blurred caustics, but I wanted this effect. By the way, this sharpened caustics with this weird grid is looking just bad, and I`m not sure what is causing this. Caustics generator (glass object) is quite smooth, and there shouldnt be any harsh lines...

But the main concern still remains. Your render is still very noisy, and no matter how much samples you will set, it will be  still noisy and splotchy... Ok. I can use a lot of samples to avoid this, but in my opinion no matter how many samples you will use, you cant get clear results.

So the main question still remains, what should I do to avoid this? Or is there something wrong in my scene that is causing this?

[RRIS]

Hi RRIS,

Thanks for your reply, but it's not the issue. I know that I had blurred caustics, but I wanted this effect. By the way, this sharpened caustics with this weird grid is looking just bad, and I`m not sure what is causing this. Caustics generator (glass object) is quite smooth, and there shouldnt be any harsh lines...

But the main concern still remains. Your render is still very noisy, and no matter how much samples you will set, it will be  still noisy and splotchy... Ok. I can use a lot of samples to avoid this, but in my opinion no matter how many samples you will use, you cant get clear results.

So the main question still remains, what should I do to avoid this? Or is there something wrong in my scene that is causing this?

Gotcha, well I would instinctively say that it could be due to the size of the photons that are used in the photon mapping (the size of the spots in the first couple of samples).. after all, there's only so much detail you can create when your brush is a certain size. But that could be completely wrong and I lack the technical know-how of how Keyshot works under the hood to give a valid answer.