There is no dedicated sampler for caustics in Karma yet.

However, you may take a look at Render Geometry Settings for caustics and fake caustics options which give control
over enabling/disabling caustics, the fake caustics color and opacity:
https://www.sidefx.com/docs/houdini/nodes/lop/rendergeometrysettings.html [www.sidefx.com]

You may try Bump Shadow Terminator [www.sidefx.com] (a H20.5 Karma CPU(only) feature) in Render Geometry Settings to soften the hard shadow line.

The Bump Shadow Terminator is H20.5 feature and Karma CPU only(atm).

The next daily build will have a fix to use the smooth goemetry normal so that the facets are not visible as in the above snapshot.

Hi,

The attached hip file has Karma LOP set up for XPU and along with the beauty pass it has an extra "unfilteredZMin" AOV with
"min" pixel filter.
Please could you check the example and let us know if this is what you're after. Thanks.

This should be fixed in the next major release of Houdini. Thank you for all your test cases

Hi timjan,
Thank you for the test scene. We are working for a possible fix on this in xpu.
I would also like to ask if you possibly could mention any further requirements (in this test scene or in your project)
in regards to the background plate node that isn't meet in xpu? Thank you.

Thank you for reporting this.
Could you submit a bug or attach the test scene, please. Thank you.

Please check tomorrow's build for the fix. And thank you for reporting the bug!

Hi Mirko,

You may try the modified hip file from this post [www.sidefx.com] where the portal geometry is added to improve the dome light sampling.

The denoiser can be enabled via
- Karma Render Settings (node) > Image Output > Filters > Denoiser , or
- Display Options > Enable Denoising

There are two denoisers available: Optix (interactive), Intel OIDN (only applies after render is completed).

Setting the denoiser also helps to remove the extra noise left in the render.

There Render Geometry Settings node has "Is Portal" set but there's no associated portal object(the opening object,box2, in sopcreate1 is subtracted from box1 to create a one room object with an opening). Please find attached .hip file that has a portal object added. This should converge quicker in terms of noise.

Also, I the main intensity parameter on Physical Sky was set to 50. This affects both sun & sky intensity. The visible patch of sunlight on the side wall acts an indirect source of light with a high intensity. This also contributes to noise level specially as there are refractive objects in the scene too. In the attached file I left the main intensity as 1 and set the Sky intensity (in sky tab) to 50 instead and Sun intensity to a lower value 7.

improvements to this has been made for the next version of Houdini.