Hello-
I'm trying to figure out how to assign material(s) to UV. There are good videos out there which describe how to set up a UV, and others which talk about materials, but I'm having trouble finding a good explanation of how to combine the two.

For example, I have created the geometry of a gear. I have created a simple UV for it using uvunwrap. I can see, in my scene view, the gear with the grey and white UV overlaid on it. I looks pretty cool, but I'd rather see something like oxidized steel and/or copper.

I'm having trouble figuring out how to get the oxidized steel and/or copper onto the UV. Or perhaps “onto the UV” isn't the right term, maybe I mean something like, map the oxidized steel and/or copper onto the gear according to the UV.

I'm saying “and/or” because it is not clear to me whether I should be mapping one or two materials to the UV. It seems to me that it would be two materials, with one corresponding to the grey area of the UV, and the other corresponding to the white area.

It's probably a simple operation, but I'm just not able to figure it out on my own. As always, your help is appreciated.
-Scott

A UV is simply a map for your materials to follow. Even though it might seem like you're trying to do very simple things, there are some very complicated concepts at work here.

At the basic level, you set up the UV map the way you want it, and then you create a material for your object. You can apply the material to your gear by simply dragging and dropping it from the MAT window unto your object in your viewer.

You don't need two materials for the grey and the white, they're just a checkered representation to make it easy to see how your map is wrapping on your object, if it was only one color it would be impossible to tell exactly what is going on.

Our of curiosity, are you just starting out or did you use another DCC app like C4D before switching to Houdini?

Hello Kays-
I tried dragging and dropping a material (oxidized steel) onto my object (the gear) in the scene view, but it didn't change anything. The gear is still just covered with the grey and white UV map.

So I guess I don't understand how materials and UV maps work together in Houdini. I don't understand the point of UV if you're just putting one material on it, like oxidized steel. What exactly are you mapping? I would have expected to place two materials on the UV, with one material in the white area, and the other in the grey area.

I've been sort of a casual off-and-on user of CG for a couple decades now. Back in the day I used programs like Raydream and Carrara. So I went from Carrara to Houdini, quite a leap because Carrara is pretty simple in comparison. Thanks again.
-Scott

Yeah, that's a bit like going from riding a scooter to racing F1.

Anyway, you need to get into the habit of posting your hip files or at the very least a screenshot which illustrates exactly what is going on and shows your node tree.

What I suspect is happening is that you added a UV Quickshade node to your node tree so that you can see the UV map, and the UV Quickshade is overriding your material. Normally you shouldn't be able to see the UV pattern on your object in the viewport.

Also….watch this to get a basic sense of how UV's work in Houdini:

https://www.youtube.com/watch?v=ZYMNkZK4E7c&t=19s [www.youtube.com]

Not the best, but honestly there's not any particularly great explanation video about UV's that I found (yet). Maybe I should make one!

P.S.

If you think UV's are confusing, wait until you find out about UDIM's!