Jonas Hagenvald

sniegockiszymon
Hey I would like to know why this is so crusial for you that you cant use karma because of that. You can mix everything before shader unless you are using the same type of shader. I've started this question deeper here https://www.sidefx.com/forum/topic/93336/ [www.sidefx.com]

I've demonstrated why in my original post here. If you look at the screenshots you can see the difference between the two methods, one using Karma CPU and mixing multiple materials, and the other using XPU mixing each individual PBR texture before going into a single material.

Simply put, it gives different results and the one in Karma CPU looks much more natural, with natural looking gradients between materials, whereas the XPU method has sharp transitions, less details and generally looks less natural to me. Not to mention, as Jacquesf mentioned, it's just easier to mix finished materials rather than multiplying each mix node by however many PBR textures you're using.

To be clear, in both cases I used exactly the same masks, the only difference is where in the node tree I placed the mix nodes. This is as clear of an example as I can give you.

All in all this is a major workflow bottleneck and I'm actually in the process of transitioning to a dedicated procedural texturing software, because I feel this Karma/MtlX workflow is currently limiting me and ultimately reducing my final render quality.

brians
Although this feature might seem trivial, sadly it requires a very large amount of work under the hood. So although we do have plans to address this, it won't be happening in the immediate term. The current design means we need to hard-code common combinations of BSDFs.

Thanks for the insight, great to know. It's unfortunate but understandable - I know Karma XPU is very different from Karma CPU under the hood so it makes sense that it takes a while to get some of these more advanced features implemented.

I suppose I'll just have to invest in a better CPU rather than relying too heavily on XPU for the moment

I realized in the presentations done so far for the Houdini 20 launch, it was mentioned that Karma XPU only supports mixing between 2 MtlX Standard Surface shaders. Any more and it turns into a regular greyshader. Meanwhile, mixing more than 2 shaders works flawlessly in Karma CPU.

As an example I've ran into this limitation while trying to use the new Hex-Tiled Triplanar texturing workflow, where I'm trying to mix multiple PBR materials on a single mesh procedurally. I can already tell that this will be a reoccurring bottleneck for me, and while mixing the individual PBR textures (albedo, roughness, displacement etc) together before inputting into a single Standard Surface shader works, it doesn't give nearly as nice of a result as mixing multiple shaders in Karma CPU. Attaching screenshots to give an example of what I'm talking about.


So my question is, is it in the plans to work on supporting more shaders in a single material for XPU? And if so would it be expected to be far down the line or could it be patched in fairly soon? Maybe it's hard to say but I would love any possible insights on this.