Join Adam Crespi for an in-depth discussion in this video Laying out the UV coordinates, part of Maya: Game Prop Creation.
I've finished unwrapping this gas pump. Everything is fairly well proportionate and all the squares are squares as I spin around and check. Now it's time to layout these UVs to make best use of my texture space. The way I've set it up is that I've got mirrored sides and fronts, and the top is unique. I've also planned it so I've got a clean texture scene here where there is a natural seam in the reference, where the top has a lip that laps over the side. On the front I've planned in that texture to correspond with the joint between the white and the red paint. So as long as I paint to it and have decent rust around, it will be a good match.
Now I'm going to lay this out. I'll go into my Texture Editor and look at stacking and laying out UVs to make the best use of this. Textures tend to be square, and they're powers of two. What we need to do then is make the best use of our texture space and accommodate possible variation in the number of objects and also wear and tear. What we're seeing here right now is that I'm out of my zero to one space, which is called the normal range. I need to stay within this so I'm always safe when exporting. Depending on where you're going, you can use the full UV range if you need, but it's better to stay within zero to one, depending on which engine you're exporting to.
This size is relative; it's not pinned to a pixel size until we do a snapshot. What I'll do is start to lay out some pieces. I'll pick my Move UV Shell tool and start to grab UVs and pull them off to the side so I can see what's going on. There are the sides and tops, and I can see that they're a little out of order. What I need to do is to flip these around so that bump maps work the same on both sides. If UVs are flipped and they're backwards, as shown here in red, bump maps that should go out will go in.
Things like flaking paint will appear to go into the object instead of sticking out from the surface. What I can do to make the selection easy here is to convert some selections back and forth so I can flip things and keep both sides aligned. Here's how I will make this work. Instead of spacing out my UVs, I'll undo. I'll get these stacked back up as they were, and I'll go and pick both fronts and move them off. Over in my viewport I can press F11 for face and pick a face. I'll spin around and pick one face on the other front.
Up here in the UV Texture Editor, I'll choose Select and select Shell. It selects all the faces in that UV shell. And I can press Ctrl+F12 and convert that selection to UVs. Then I can move them using the Move UV Shell tool off, and there are both fronts and both sides now separate. Now I can deal with the backwards-facing UVs. I can see that A, B, C, and D are flipped here. That's why I put those letters in that UV map, so I can tell which way it's facing. What I will do is use the same technique, only picking one side and flipping it.
I'll pick one face and here under Select, choose Select Shell. I'll press Ctrl+F12 to convert to the UV Shell and choose Polygons > Flip. They flip around but are still stacked. Whether we use all of it or not, we're still loading this texture space in memory. My plan then is to stack these UVs. That way they share texture on fronts and sides, and I can get more detail painted in that UV space. Then I'll get these arranged and laid out once they're all stacked in and see what else I have space for.
Because it's a gas pump, I need to allot some space in here eventually for a hose and nozzle. Or maybe there's another fitting I want to end up using. I'll repeat this process on the sides, looking for this side that's backwards. There it is, and I will pick that face. I'll choose Select > Select Shell and Ctrl+F12. Then I'll take this face and choose Polygons > Flip. Now I've got the sides stacked, and I can start to lay this out. I'll use my Move UV Shell tool. I'll pick these shells and slide them over next to the fronts.
This way I've got some continuity I can paint across here if needed. Finally, I'll pick the top and press R for Scale. After all that work to get it proportionate, I want to make sure I'm scaling uniformly, so I'm going to click in the middle and scale it down. I'll move it over and place it in right here. It's a decent layout. The one last thing to do is to make sure these shells are not touching the edge. I've got some leftover space here, which I can probably use for something else like a tool or maybe there is a tire or maybe there is an air and water nozzle or something else that I can use here.
What I do need to do so it imports properly into Unity is make sure I select these shells and scale them down. Unity tends to have issues if shells are touching the edge of the UV space, so I'm going to pull them down slightly and then move them over, just making sure they're inside. I want to give myself a little bit of a margin here. That way, depending on the size of this texture, if this comes near the edge, it's still going to be okay. I'm ready to snap-shot this and start painting.
I'll save this model. Then I'll figure out how big to paint and start in on first the clean paint and then to the general wear and tear. This is a fairly easy object to model. Really what I'm after when I'm modeling props is that I'm using my texture space elegantly, and I'm modeling to get the right silhouette and the right number of curves in the model, keeping it low poly. We can still spend some faces where we need, on key contours, to make sure it really looks like the model it's supposed to, watching out for the hallmarks of the design, things like those round corners and slight tapered shape that really denote it as Art Deco.
It's going to match in with my gas station nicely. And I'll be able to paint on it easily, and my UVs are laid out cleanly so that I get distortion-free rust and general grime on my gas pump when I'm all done.
- Planning for modular textures and models
- Blocking out the overall form of a prop
- Moving and sewing UVs
- Laying out UV coordinates
- Texturing with bump maps
- Converting bump maps to normal maps
- Unwrapping and cloning objects
- Breaking up a model for texturing
- Painting textures from scratch
- Adding detail with beveling and extruding
- Baking high poly model onto a low poly model
- Painting in Mudbox
- Importing and assigning objects and maps in Unity
- Adding lights in Unity