Karma XPU, Matt Shadow catcher

Forums Technical Discussion Karma XPU, Matt Shadow catcher

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Tser: Member; 89 posts; Joined: Dec. 2014; Offline

Oct. 12, 2025 11:13 p.m.

My XPU Shadow Catcher is created in the Object level, so the shadows and AO are present in the scene for other scene objects to react to, so you can see the shadows in reflections/refraction's in the beauty pass, no compositing needed, it works just like all other Renderers Shadow Catcher, you also have full control over the shadow quality. It works with any 360deg HDRimage, the ones I use are from https://polyhaven.com/hdris [polyhaven.com]


Tser: Member; 89 posts; Joined: Dec. 2014; Offline

Oct. 14, 2025 10:33 p.m.

Did some more work on the shader and some more tweaking, left is XPU, right is Arnold.

Attachments:
Arnold_XPU_Comparison_4.png (5.2 MB)


Mirko Jankovic: Member; 277 posts; Joined: Aug. 2015; Offline

Oct. 14, 2025 11:51 p.m.

Does your shader handle matte properly??
Currently there is problem with shadowcatcher in H21,I;ve submitted bug a while ago:

In this case, grid is shadowcatcher and torus is matte. But instead having full matte torus still show shadows on it.
Does your shader handle situation like this properly?

Attachments:
shadow_matte.png (1.4 MB)


Tser: Member; 89 posts; Joined: Dec. 2014; Offline

Oct. 15, 2025 8:23 p.m.

Hi Mirko Jankovic, My Shadow Catcher has no issues related to the Shadow Catcher which comes with Houdini 21, My Shadow Catcher is in the Object level and is rendered with all the objects in the scene so the scene reacts to the shadows as they are really there, no compositing required, it's all in the beauty pass, my Shadow Catcher is a hda and is a single node, all the environment mapping, catcher grid and material are included, just select your hdri, select the objects you want to cast shadows from, import the ShadowCatcher node and your Objects into the Stage and Render with XPU, very easy, also you can store Recipes of the ShadowCatcher node with all your settings and HDRI to recreate any time, I have parameter settings to adjust the Shadow/AO, Light, Environment, Grid etc to suit any HDR image environment, I've been working on this for a couple of years on and off, but now I'm pleased with the results, no need for my Arnold Renderer any more.

Attachments:
Ford_1934_AbandonedGH_Front_Latest_1.png (9.6 MB)


Tser: Member; 89 posts; Joined: Dec. 2014; Offline

Oct. 15, 2025 9:10 p.m.

Seems to work fine...

Attachments:
Matte_Torus_Test_1.png (4.3 MB)
Matte_Torus_Test_2.png (4.3 MB)
Matte_Torus_Test_3.png (4.3 MB)


Tser: Member; 89 posts; Joined: Dec. 2014; Offline

Oct. 15, 2025 10:35 p.m.

Same scene but with the parameters of the AO/Shadow tweaked

Attachments:
Matte_Torus_Test_4.png (4.1 MB)


Tser: Member; 89 posts; Joined: Dec. 2014; Offline

Oct. 15, 2025 10:51 p.m.

The Matte torus shows up in reflections, is this normal?

Attachments:
Matte_Torus_Test_5.png (4.1 MB)


Mirko Jankovic: Member; 277 posts; Joined: Aug. 2015; Offline

Oct. 16, 2025 4:17 a.m.

That actually looks perfect!

Ok @SideFX... buy this and implement!


Tser: Member; 89 posts; Joined: Dec. 2014; Offline

Oct. 16, 2025 5:30 p.m.

It's very easy to match the shadows in the HDRI

Attachments:
Matte_Torus_Test_7.png (3.4 MB)


Mirko Jankovic: Member; 277 posts; Joined: Aug. 2015; Offline

Oct. 17, 2025 4:17 a.m.

Any plans to put that on gumroad maybe>?

With nice video tutor or documents to speed people in, why not to monetize your effort a bit, and help others as well.


Tser: Member; 89 posts; Joined: Dec. 2014; Offline

Oct. 17, 2025 5:14 p.m.

I'm in the process of dialing in all the parameters and refining, optimizing everything to make it perfect, I wouldn't know anything about monetizing it, but that does sound attractive...

Attachments:
Test_8.png (4.0 MB)


Tser: Member; 89 posts; Joined: Dec. 2014; Offline

Oct. 17, 2025 5:50 p.m.

A bit of moving around the scene

Attachments:
Compressed_4.mp4 (10.3 MB)


Tser: Member; 89 posts; Joined: Dec. 2014; Offline

Oct. 23, 2025 7:09 p.m.

Still Tweaking...

Attachments:
Compressed_7.mp4 (437.6 KB)


Tser: Member; 89 posts; Joined: Dec. 2014; Offline

Oct. 25, 2025 7:55 p.m.

Still tweaking...

Attachments:
Compressed_8.mp4 (1.2 MB)


Tser: Member; 89 posts; Joined: Dec. 2014; Offline

Oct. 25, 2025 8:53 p.m.

Another HDRI...

Attachments:
Compressed_9.mp4 (1.3 MB)


Tser: Member; 89 posts; Joined: Dec. 2014; Offline

Nov. 6, 2025 5:09 p.m.

Hi Guy's, well I have the shadow catcher as good as I can possibly do, but I cannot find a way to blackbox it so that I can make a couple of dollars on Gumroad, I can blackbox the nodes, but they won't work importing into Stage, any suggestions? I just don't want to give all my hard work away to others who can resell it as their own.

Edited by Tser - Nov. 6, 2025 17:28:01

Attachments:
Compressed_10.mp4 (2.2 MB)


Tser: Member; 89 posts; Joined: Dec. 2014; Offline

Dec. 7, 2025 6:43 p.m.

Will be releasing my ShadowCatcher on Gumroad in a couple of weeks, it's a blackboxed Lop node which is directly added to the Solaris /stage context from the Digital Assets tab menu, it is very fast, at it's highest quality setting it only takes a second to create the Shadow/AO just before the render begins, with lower quality settings it takes a fraction of a second, it is multi threaded CPU, my CPU is a Threadripper 24core @ 4GHz, any higher clocked CPU will be even faster. All you need to setup a scene is a Grid to catch the Shadows/AO, a HDR image for the environment map and your objects you want to cast Shadows/AO from. I have created 8 video's to help with setting up a scene. The ShadowCatcher was designed to work with Karma XPU, but it works equally with Karma CPU, I haven't tested it with any other renderer, it uses a MaterialX material, so if a renderer can utilize this material then it should work.

Attachments:
Ford_1934_XPU_BLagoon_19.png (8.2 MB)


Tser: Member; 89 posts; Joined: Dec. 2014; Offline

Dec. 9, 2025 7:16 p.m.

Well I have released it a bit earlier than expected, I've just spent days of constant testing to make sure it does what it's supposed to, I had an issue with the catching Grid loosing the material, but only if I had the blackboxed version on it's own in the /otls folder, if the un-blackboxed version was in the folder also there was no issues, go figure, but it has been tested on multiple machines now with the blackboxed hda only in the /otls folder and all is well.
The Gumroad page is:
https://houdinishadowcatcher.gumroad.com/l/gggwv [houdinishadowcatcher.gumroad.com]
I hope you like it...


Mirko Jankovic: Member; 277 posts; Joined: Aug. 2015; Offline

Dec. 9, 2025 11:40 p.m.

"All you need is a Grid to catch the Shadows, an Environment image (eg. HDRI) to cast the rays and Objects you want to cast Shadows from."

Just to check, catcher can only be grid or it can be any other object in the scene as well?
I mean wording seems a bit exclusive to grid so figured to check.


Tser: Member; 89 posts; Joined: Dec. 2014; Offline

Dec. 10, 2025 12:58 a.m.

Mirko Jankovic
"All you need is a Grid to catch the Shadows, an Environment image (eg. HDRI) to cast the rays and Objects you want to cast Shadows from."

Just to check, catcher can only be grid or it can be any other object in the scene as well?
I mean wording seems a bit exclusive to grid so figured to check.

Catcher was designed on a Grid and the algorithm automatically trims up the Grid like trimming off fat from a piece of steak, but, I created a sphere Radius 50x10x50 Center 0x-10x0 with Rows/Columns = 50 and used it instead of the Grid and it worked, as you can see, the underside of the squashed sphere also catches the Shadow, I don't think it would be a good idea to have a 3D object catching the Shadows, but a 2D object (without a bottom) would be fine:

Edited by Tser - Dec. 10, 2025 01:03:37

Attachments:
CarOnSphere_1.png (3.6 MB)
CarOnSphere_2.png (3.6 MB)

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