Is the MaterialX blur broken? I can't get it to blur anything.

I don't think those Convolution nodes can really work with a shading pipeline:

https://www.materialx.org/assets/MaterialX.v1.38.Spec.pdf
Convolution Nodes
Convolution nodes have one input named "in", and apply a defined convolution function on the input
stream. Some of these nodes may not be implementable in ray tracing applications; they are provided for
the benefit of purely 2D image processing applications.
● blur: a convolution blur.

Hmm, interesting. So that particular node wouldn't have any application in Solaris?

I wonder if use immediately following an image node could be interpreted as texture blur.

Seems like that's what it should do. I know blurs aren't very common in other renderers since it eats up a lot of processing power. Was just curious since I saw the MaterialX node in Solaris. Maybe SideFX should update the docs to say it doesn't do anything.

jsmack
I wonder if use immediately following an image node could be interpreted as texture blur.

I didn't see anything in the spec that suggests that, but I could have missed it.

I think I'd rather petition the MaterialX council for some Mtlx Tiled Image read-time filters, perhaps in the style of the VEX texture() variadics that we've been spoiled with over the years.

Sorry, missed a few of the compositing/image operations which are unsupported. Should be fixed in the next cut of the docs.

jsmack
I wonder if use immediately following an image node could be interpreted as texture blur.

Yes it should. I remember an early Arnold shader, that did exactly that. Worked with textures and procedural noises. It was quite expensive though.

Andy_23
Yes it should. I remember an early Arnold shader, that did exactly that. Worked with textures and procedural noises. It was quite expensive though

Interesting that they implemented this... yeah, this sounds like it's not doing a "texture blur" per se, but rather a true convolution where you execute the shader multiple times on the texture generation (jittering/moving the texture space, all sans illumination) and average it up. Can be very expensive, yes. I know someone who needed to do this on the procedural shading for the tunnels in The Matrix because trying to figure out the analytical filtering for his effect was just too hard, and brute-forcing it was feasible. While convolution is cool, I can imagine the added complexity and potential to make your renders very slow could dissuade implementation when a fast renderer needs to maintain reputation. Does Arnold still provide this?

I did something like this once myself on thresholded procedural noise while offsetting and evolving the noise to see an aurora effect for the "time bubble" in

Hmm. I really wish they would implement this. Render power is not a problem these days, expensive or not is the user decision to use it or not. I really need this feature to blur out the curvature of an object for example. I do not want to or can not use the curvature node because it changes globally everything so i need to blur ONLY the curvature mask i defined already. Yes in ideal case you would have texture maps and all, but for hard surface industrial stuff with dozes of millions of poly is not fessable or practical and you simply have no time to optimize and make good texture maps so procedural mapping IS the only practical way.
I am searching forhours and hours a way to blur my curvature edge in karma CPU not even xpu, and no luck. Seriously people, this is a 20221 thread and this node still does not work.