uv mapping 101 – part 2

This tutorial follows the dice texturing tutorial that showed how a file texture can be mapped to the different faces of a cube. Download the spaceship scene file and open it in Maya. This process is rather tedious and takes time.

1. Open the spaceship file . You can see a rough version of the model that has not been smoothed yet.

2. You can apply a PolySmooth (Polygons >Smooth) to see what the model looks like when it’s smoothed. Because selecting faces on the rough model is easier we will use the rough model to map the UVs and then we will smooth the model before painting it.

3. Use the paint selection tool to select faces. Right click on the object to be in face selection mode and choose Edit > Paint Selection. The brush appears and you can select faces. This goes faster than selecting faces one by one and it prevents selecting faces that are at the back of the model. Once you have a section selected choose Create > Sets > Quick Select Sets and create a set for the major parts of the spaceship. You have to be able to analyze the model and come up with your own slicing of the model.

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4. Make sure you have delected everything before building a new selection when using the Paint Selection tool! It’s easy to create a set and then add to it unvoluntarily and create a new set that includes the previous one (I can’t think of a project where I spaced out thinking how cool the paint selection tool was and I had to redo some sets afterwards). If it happens to you, delete the set in the outliner and build the set again.

5. Once you are done building the sets it’s time to save with a different file name. And let’s take a look at the UV Texture Editor. There’s not much going on there. UVs need to be organized to allow us to paint a flat texture map in Photoshop. So we are going to unwrap the spaceship as if it was built with cardboard.

6. Because we want to see any weird texture stretching and tearing that would appear assign a material with a checker texture to the spaceship.

7. Select the Quick Select Set ( Edit > Quick Select Sets ) that you created for the top of the spaceship and choose Edit Polygons > Texture > Planar Projection and you should have something like the following result.

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8. If by any chance you lose the manipulator for the projection select it in the Channel Box or the Hypergraph and press T or click on the Show Manipulator button. This should bring back the projection gizmo.

9. Turn on the hardware texturing (Shading > Hardware Texturing) to see how the checkered patterned is distributed across the surface. Adjust the size of the projection manipulator to have something like this.

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10. Move on to the next set of faces (bottom for instance) and apply projections. Everytime you create a projection look right away in the UV Texture Editor to see how the set of faces is laid out there. You can usually move the set out of the way to have a better look at it. Also experiment with the different projection modes. The Automatic Projection can be quite handy as it doesn’t generate much distortion. As shown below the Planar Projection can be done along different axis

11. If you choose to use the Automatic Mapping you probably will end up with different pieces as below. In the UV Texture Editor right click to select the edges and Sew them or Move & Sew them. Sometimes you can select only one face on the model, do a planar projection on that face and sew the UVs of that particular face to another piece in the UV Texture Editor.

12. As you project and assemble the UV set in the UV texture editor it’s important to keep the checker texture even across the surface of the model. If the checker texture starts to smear or tear it’s a sign that your UVs are not laid out correctly and any texture you will paint later in Photoshop will also smear when applied to the model. Instead, the checker texture should look like this on your model, as if it’s evenly distributed. Also be patient, it takes time to get it all right. Unfortunately there’s no button that does that automatically for you.

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13. When you are done laying out all the UVs from the spaceship your UV set should look like this. Select all the UVs and arrange them all in the texture space (the upper right square grid of the UV Texture Editor).

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14. Now you can smooth the model and you will see that the UVs get smoothed too. Now you need to export the UV set for painting in Photoshop. In the UV Texture Editor Choose Polygons > UV Snapshot and save the file (it should be saved in your project folder) – I used a resolution of 1024 x 1024 which is a minimum for painting a texture. It’s easier to paint a texture at high resolution and shrink it down later. I also chose to save it to the Maya IFF format because it has an alpha channel.

15. Open the file in Photoshop. At this stage I usually resave it in my texture folder and I apply it to the object to check the alignment of the UV set with the vertices and edges.

click for larger image

click for larger image

16. And now the fun actually begins. We can start painting the texture in Photoshop Get a tablet because mice are not made for painting! Also tons of stock textures are available online and also use your digital camera to sample real life textures. Also it’s a good idea to have just the lines of the UV set on top of all the layers in Photoshop and paint on the layers below. Save the texture file often (without the UV lines of course!) and check how it looks in Maya (go to the attribute editor for the material and reload the file texture).

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17. Render the model.

Conclusion: you have practiced on a dice and on a simple spaceship how to lay out UVs and texture a model. UV mapping is pretty much something one needs to practice a lot as well as texture painting. Here I rendered the spaceship using mental ray and I added some glass spheres with a glow.

What I should also have painted and applied to the model is a bump map and possibly specular and reflection maps. Those texture maps would use the same UV set as the Color map. See below an example of a UV map for Rodax, one of Cleaners characters.

click for larger image

click for larger image

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