Hi

Houdini newbie here. I'm trying out the materials from the material pane and when I got to marble I get no image when I render. It doesn't matter whether I use it by itself or with other materials nor what kind of object I put it on.

Also, can anybody direct me to some tutorials on the VEX.

Thanks

Marble seems busted to me, I've already moaned about it but no response. It's not you. Basically, it takes forever to generate a map pass (which needs optimization) then when it does render it typically looks solid white - the subsurface layer defaults to far too hot. Also, no work has been done yet to put in veins, which I think the typical user expects.
Most of the other shaders are in a reasonable state, though. You just hit a minefield. I really think it should be removed until it's somewhat usable.
Cheers
JC

Thanks for the reply.

I'm trying to build my own simple marble shader. I have one started but I'm stuck trying to figure out how to wire in some reflectivity. I'm finding it hard to translate old tutorials into the new shader model. Nodes that they use aren't present anymore.

It's very different, yes. Really, it's the lighting models that have changed the most. There are, however, new basic shaders that you can start with if you want to roll your own. The official SESI suggestion is to start with a Mantra Surface from the shader gallery, I personally find that too constricted because the moment you want to customize it, you're stuck with all that multi-renderer-compatible crap inside and just becomes messy. It's handy for fast exploring though. What I prefer to do is make a Material Shader Builder, and stuff a surface model VOP inside of that. That gets you a good chunk of the way along. You have two layers of reflectivity you can assign, and there's SSS there. I still need to crack that open to get the speed acceptable for SSS, but it's a good start.

Cheers,

J.C.

P.S. if I get a sec, I'll clean up and upload an SSS file I was playing with during beta. It's not marble, it's more ceramic, but things like reflections, SSS are all there. I've become a PBR evangelist, but very, very frequently out of the box it's performance-deficient. It typically needs some tweaking and there are several potential pitfalls.

Since we're on this subject: any tips on using the new SSS stuff when starting from scratch under PBR? I've looked at the mantra surface material but I can't make sense of what exactly is going on with regards to subsurface scattering. The Physical SSS VOP doesn't have a bsdf output, and then there's the new, un-documented VOPs like fakealbedo, direct/indirect lighting etc.
The mantra surface and Surface Model are nice, but I'm not a big fan ubershaders and it's getting a bit too blackbox-ish for me (not really a fair statement since all the nodes are right there, it's just I find it confusing as hell).

After the first time you render, be sure to change /shop/dragon/surfacemodel1/Subsurface/Point Cloud Mode to Read From File, to speed up renders. Note that with non-deforming surfaces, you want to only write out one point cloud that is used throughout the animation despite the model translating.

I did kick open the Surface VOP node and change a couple of things - go into the “if2” node inside the SSS section of the network and look at the physicalsss2 node. I click on the two Optimize Secondary Rays in the single and multiple scattering tabs. This has a massive effect on render times with a negligible difference in look. IMHO they should default to on. Also, if for any reason you find you need to bump the samples on your lights up to fixx SSS problems, take a look at the Multiple Scattering/Global Light Quality setting, which defaults to 1. Basically, this hacks the sampling on the lights up *just* for SSS, and nothing else, so you don't need to take a global hit just to fix an SSS issue.

Other than that, the Surface Model VOP sort of speaks for itself - you can see reflections of the envlight in the surface, etc. Hope it's useful.

Cheers,

J.C.

DaJuice, I believe Physical SSS is added as an emission, as opposed to having a bsdf output. I'm not sure about the other VOPs you refer to - there is indeed a fakealbedo VOP, undocumented, but that's not the VOP that's in the Surface Model VOP - it's just called that, and is a multiply VOP. Direct and Indirect lighting are all tied up in PBR.

I hear you about black box shaders, which indeed is exactly why SESI didn't do it - they are exposed on the atomic level. Now, it's perfectly true that digging through them isn't necessarily trivial. One of the contentious issues during testing was the decision to make a ‘one model fits all render engines’ solution. The upside is, you can throw down one regardless of render engine. The downside, which many of us stated, was a more cluttered network and some parameters which just “don't work” because they don't apply to a particular engine. Personally, I would have liked a Surface Model for each engine. <shrug>

Cheers,

J.C.

I've attached a hip file with a marble shader I was messing around with a while ago. It needs a bunch of work but it might get you started. I haven't promoted any of the parameters from the VOPs so you'll have to do that yourself or adjust the parameters on the VOPs themselves. As well, you'll need to use the kr output of the Physical SSS VOP to do something with the light reflected at the surface. If you find it useful and are able to tweak it to make it more complete/usable, perhaps we can replace the gallery entry with it.

John, that pretty much clears everything up with regards to SSS. I never really mess with Ce so I completely forgot about that. Thank you!

This is what I got so far:



Like this:



Its my newbie shader. Still not sure if the reflectivity is showing up.

My new and improved marble. Added in subsurface scattering.



Still working on proper vein size.

Comments welcome.

Thanks