There's too much difference between CPU and XPU as for the lighting. Can this be fixed?
Check my pic

Does the floor have a material or is the ight a prjector?

If the floor has a material try remaking it as a materialX material.

Yes, the floor has a material X network inside a material library stage node. I really don't understand what's going on here. Other Houdini users have exactly the same lighting between CPU and XPU?

For the most part they match. There are some subtle differences in how fresnel is computed and energy is conserved, but they should be the same for the most part. Some bugs were causing them to be different under some circumstances, some of which have been fixed. Normal maps on right-handed geometry were being interpreted in opposite ways between XPU and CPU, but that should be fixed now. XPU was not conserving energy correctly in glancing reflections, which also should be fixed in recent versions. There was a bug that was found recently where color temperature enabled on a light causes the light color attribute to be ignored under XPU. Is that what you're seeing here?

XPU and CPU don't have a fully overlapping feature set, so if you're using features that don't exist under XPU obviously they will look different. Both of your renders are using XPU supported materials and lights?

Hello Jsmack, thanks for your help.

Recently I simplified my scene using a simple grid as a ground, and I replaced my 3 lights system by a simple distant light that does not use color temperature. I found this light on the "LOP Lights and Camera" shelf. Are these lights different from the one in the regular "Lights and Camera" shelf? They don't seem so. But the light I kept should be compatible with Karma XPU.

I think the material I use on the ground should be compatible with XPU as it is a MTLX network.

AND I upgraded to Houdini 19.0.622.

Still the same problem.

I'm enclosing a zip file with my scene and textures in case someone has the time to look at it...

Thanks!

G

Grendizer
Hello Jsmack, thanks for your help.

Recently I simplified my scene using a simple grid as a ground, and I replaced my 3 lights system by a simple distant light that does not use color temperature. I found this light on the "LOP Lights and Camera" shelf. Are these lights different from the one in the regular "Lights and Camera" shelf? They don't seem so. But the light I kept should be compatible with Karma XPU.

I think the material I use on the ground should be compatible with XPU as it is a MTLX network.

AND I upgraded to Houdini 19.0.622.

Still the same problem.

I'm enclosing a zip file with my scene and textures in case someone has the time to look at it...

Thanks!

G

The ground plane doesn't have uv coordinates. Karma CPU treats each patch as its own uv space but XPU treats each micropolygon as a uv tile so each uv tile is only one pixel large. I recommend using proper uv coordinates instead of relying on the implicit ones for polygonal surfaces.

Edit:

Also, keep in mind the subsurface component of the standard surface is not supported in XPU. It appear as a simple diffuse term instead.

Ah, thanks a lot. I added UV's. That seems to have fixed it!

Hello, I'm doing more tests with comparing Karma CPU and XPU. I have found 2 more differences. Please check the attached pictures. Can these be fixed or are they more XPU limitations?
Thanks

Better light bounces

can you please post a scene for these latest lighting issues?
thanks!

Here you go. There's a note inside the stage.
The related files are in the zip file above : Cupboard_4Cigi.zip

I've tested on my latest development code.
There was quite a difference until I enabled the material library (ie without material library it was using principled shader).
With the material library enabled I get a close match.

I can't say the match is now 100% (its not), but in the next version of Houdini it'll be a closer than what you're currently experiencing with H19. You could probably apply to be a beta tester if you like?

Thanks for the test cases.
I've made at least one ticket from them (grazing-angle rough surfaces are still an issue :/)

Thanks!
Brian

Thanks a lot Brian. I'm looking forward to the next Hou version!!
To become a tester, should I email support?