UV Lesson from Angela Yi

Hello! My name is Angela and Grant has given me the chance to write a guest entry in his blog. I thought I would talk a little bit about UV mapping.

What is UV mapping?

UV mapping “is the 3D modeling process of making a 2D image representation of a 3D model” (UV mapping, 2011). If you want to get technical with it, it is hard to explain and there are even math equations to for finding UV coordinates for a sphere. The reason why the letters U and V are used, is because “X, Y, and Z are already used to describe the 3d object in model space” (UV mapping 2011). Once your 3D model is mapped out, you can then save this file and export it into Photoshop to apply textures or colors. Then, you bring it back in to Maya and lay the texture on top of your model.

Let me show you a quick example of how to texture a sphere with the world map.

The first thing I did was create a simple sphere.

Then I clicked on WINDOW > UV TEXTURE EDITOR

You should get something that looks like this.

Once the window UV Texture Editor window is open, I held the right mouse button and clicked UV. Then I highlighted all of the white squares. The image of the world map is not square but a rectangle shape so after clicking all of the white squares, or the UV’s, I scaled it to the best of my judgment to match the shape of the world map image. 

Then within the UV Texture Editor window, click POLYGONS > UV SNAPSHOT and save it to somewhere you can easily find it, like the desktop. The UV’s must be selected or else it won’t let you save the image.

Next open the UV Snapshot and the image of the world map with Photoshop.

Copy the image of the world map, and paste it onto the UV Snapshot image.

Next what I did was, take the UV Snapshot image, and invert it (Ctrl or Cmd + I) so that it is a white image. I placed the image of the world map layer on top of the UV snapshot image. Then scale the image of the world map to within the borders of the UV snapshot.

Next, save this image to an easily locatable file. Make sure that the UV Snapshot image is NOT visible, or else you will see lines on your 3D model texture.

Next I right clicked on the sphere in Maya, and clicked on ASSIGN NEW MATERIAL.

I decided to use a Phong shader. After that under the color tab, you click on the 4 checkered box on the right side, and then click on FILE. Then choose the file where you saved your Photoshop image and hit “6” on your keyboard.

There you have it! You have textured the world!


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UV Lesson from Amanda Jagielski

Amanda is studying Arts & Technology at The University of Texas at Dallas. We’re lucky enough to have her visit and write an explanation of what are called UVs. So here she goes:

When you have a completed model, the next task is to cover it in textures and colors. In order to do this, you need to lay out your model on a flat surface – a process called UV mapping. Imagine your 3D model as being cut into pieces and laid out flat, so you can paint onto it.

Here is a visual of what the UV mapping process looks like, with the completed model on the left and the UV map on the right. I’ll call this a tail wing from now on.

In order to see this map, open the UV Texture Editor by going to Window > UV Texture Editor. This displays all of the UVs of your object. With the mouse in this window, right-click and select UV – this allows you to select the UV points. UV points do not affect the geometry’s makeup (position) but rather how the texture will cover your object. You can move these points just like they were vertices, but remember: you are moving the “map” of where your object is laid out, and not your actual geometry. More details on this later.

Now here are steps to get started with UV mapping.

  1. Click on your 3D model while in Object Mode.
  2. Open the UV Texture Editor (under the Window tab).
    1. Here is an example of the tail wing, before it has been mapped out.

  1. Look at your object, and see if it has a surface that is relatively flat. For that part, you can use a Planar Projection. Select the individual faces that are “flat,” similar to the picture below (I selected the top of the tail wing).

  1. With the faces still selected, go to Create UVs > Planar Mapping > box on the right (see below – it is the options box highlighted in blue).

  1. Then, choose which direction you want the planar projection to project from. For this top view, I’ll use the Y axis.
    1. The projection (the mapping) will appear, and you can now look at the UV Texture Editor to see the results. Basically, Maya tries to fit your selected faces onto a flat square. You’ll need to stretch out the box so that your object’s texture does not get “stretched” in awkward directions.

  1. With your UVs moved, and the UV green dots all selected, now you can manipulate them to see how your object is mapped. To see the stretching, put a texture on your object.
    1. Go to Window > Rendering Editors > Hypershade.
    2. Click on “Lambert” on the left to create a new Lambert shade.
    3. Double-click on the lambert you just created in the Materials section on the right.
    4. Back in the original Maya window, a side bar appears for that lambert.
    5. For color, click on the checkered box on the right (see below).

    1. Click on the Checker pattern.
    2. On the Projection Attributes, after image, click the arrow and box (see below).

    1. Now, select two colors; one light, and one dark. By having a checkered pattern, you can see if the squares are stretched or not.
    2. Now apply that texture to your object. (In the Hypershade window, drag and drop the lambert using the middle scroll button, or right-click and select Assign Material to Selection).

7.    Now, you can use the Scale Tool and Move Tool to move the UVs. I took some UVs        and scaled them out, so that the stretching went away (see image below).

 

  1. Now, repeat this process for any more surfaces that look like a planar mapping would work, as in, the faces are relatively flat.

Other Projections

For your model, a planar mapping won’t always work. There are other mapping options available. These still use the UV Texture Editor and the same tools; the difference is that your object is not flat and it needs a different-shaped projection for its texture.

  • Cylindrical Mapping: Use this for model sections that resemble a cylinder, tube, or round shape. This works well for a robot’s tube-like arm, but not for a sphere (because at the poles, the cylindrical mapping creates a lot of stretching). To see a video tutorial of this, visit: http://vimeo.com/8332500 (Start at 2:30 to skip the intro)
  • Spherical Mapping: Use this for spheres or circular shapes. This may or may not work for the entire sphere, but it will help get a larger connected map with fewer seams than if you did just planar mapping.
  • Automatic Mapping: This is where Maya uses a lot of planar projections and places them all over your model. It creates a lot of seams, so you will have a very hard time texturing on the object. It’s as if you have to make a painting, but your solid canvas has been cut into puzzle pieces that can’t be lined up. Automatic mapping is best used only if that area will be a solid color (because then seams do not matter).

A good video to see the difference between these mapping tools can be found at eHow: http://www.ehow.com/video_4445138_using-uv-mapping-maya.html

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Non-linear Animation Deformers

This is a video podcast discussing Maya’s Non-linear Animation Deformers.

Explanation of the sine function

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Snap to Grid – A Useful Trick

The idea here is that you can select multiple objects, and move them all to the same geometric plane. Here’s a visual example:

To do this, 3 steps are necessary.

1. Go to the settings for the move tool and uncheck “Retain component spacing”.
2. Turn on Snap to Grid by clicking this button at the top of the window. The default hotkey is x.
3. Select the objects you want to move (they can be lines, vertices, separate pieces of geometry, or anything else). and move them. They’ll jump to the mouse, and then you can move them wherever you please.

If you grab the middle of the grab tool, all the objects you’ve grabbed will converge at the same point. If you grab one of the handles, they’ll all move to the same plane on that axis.

Have fun!

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Input from Vincent Lo

Vincent Lo is studying in the Arts & Technology field at UT Dallas. He answered a few questions for us. Enjoy!
How long have you been using Maya, and what do you specialize in?

I’ve been using Maya for almost two years. I’m currently trying to find out what I’m best at. I’ve only worked with a bit of modeling, texturing, lighting, and rigging. I’d say I’m a bit of a generalist, but friends say I have a knack for modeling. And, as for rigging, I find it tedious… But I do respect what they do. They make it possible for animations to be amazing (or bad).

What were some key insights that helped you learn and grow in Maya?

One thing that I’ve learned to be really helpful is hotkeys. For the longest time, I didn’t bother using them up because I didn’t want to spend the time to go and set them up. What I didn’t realize was how much faster my workflow went after setting up a few.

I’ve also learned from working on some animations that all the aspects of production (modeling, texturing, rigging, etc.) are all closely connected. For example, the way you model something can simplify or complicate texturing. The way you model can also affect rigging.

A big part of learning is just practice. And the more practice you get, the better you’ll get. And plus, learning about the different areas of production can help you pass down better, efficient files in the production pipeline. This way, you can avoid future problems and get animations done faster.

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Different Shading Methods

Much of 3D graphics is centered around getting 2D images.

Flat

Flat shading generates a single value (darkness or lightness) of each face based on its orientation to the lights in the scene. 1

Blinn

Blinn shaders use the normals of a surface to calculate the value of the surface and reflections. 2

Phong

Phong shaders are like Blinn shaders, but use a different algorithm to determine reflections. The reflections are tighter and brighter. 3

Gouraud

Gouraud shading smoothes out the edges of the polygons, but isn’t very powerful in the long run. 4

Ambient Occlusion

Ambient Occlusion works in conjunction with a shader to add subtle shadows where they would be in reality. 5

1. SHADING: Flat (aka Lambertian, Cosine or Uniform) Shading. October 2010. http://courses.be.washington.edu/ARCH/481/1.Tapestry%20Reader/2.Rendering/4.Shading/2.Flat%20Shading.html

2. Blinn Shader.  http://www.kxcad.net/autodesk/3ds_max/Autodesk_3ds_Max_9_Reference/blinn_shader.html

3. Phong Shader. http://www.kxcad.net/autodesk/3ds_max/Autodesk_3ds_Max_9_Reference/phong_shader.html

4. Gouraud Shading. http://freespace.virgin.net/hugo.elias/graphics/x_polygo.htm

5. Ambient Occlusion. http://www.game-artist.net/forums/spotlight-articles/1317-tutorial-ambient-occlusion-maya-alchemist101.html

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Input from the Audience

Yash Sharma is Biology a student at UT Dallas. Movies are a hobby of his. He offered his insights as a knowledgeable member of our target audience.

What are some movies you’ve seen in which the computer graphics make a valuable contribution?

In Pirates of the Carribean, the work done on Davey Jones is incredible. There is no make-up work at all. Computer graphics is done well when the audience can choose to admire it or go along with the story – or in my case, both. They completely pulled it off in that movie.

The ability to create impossible worlds with seamless realism adds a whole new level of audience involvement. Its great to be in a generation of movie-goers who get to see this stuff in its infancy.

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