Maya: UV Mapping Polygons                 by Eric Siu

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mental_ray02
smallarrows.GIF

UV Poly mapping (Dice)
Create a polygon cube with single division on each side.

Create a Blinn material in  Hypershade.
Map dice_texture.tif to the color of the blinn material.
Assign the material to the cube.
Press key 6 to show texture in the view.

You will see you the texture is not mapping correctly. The dot on the dice are stretched and 2 faces on the side appeared as empty green.

To fix this problem, you can select individual faces and assign individual texture, but that means you need 6 materials for one object, which is very inconvenient.
Here, we try to modify the UV mapping to solve the problem, and have the object use only one material.

Make sure the cube is selected, and open Windows > Modeling Editors > UV Editor.

Dolly out
Right mouse key menu > Select UV

marquee select all the UVs.

Note: all transform tools you use to move, rotate and scale objects apply to UV Texture Editor.

Now, click on Modify->Rotate-> (option box). Enter 180 for the Rotation angle and click Apply, .
 

Scale the UV in X and move to match up with the texture as shown below.

Now, the dots on the cube are no longer stretched, but we still have two faces missing.

Right click select face.
Select the top left face and right face.
In the UV Texture Editor's menu bar select Cut/Sew->Cut

uvte_05

These two faces are now separate UV components.

uvte_06

Right click select UV Shell.
Move the UVs to fit the texture. To get your UVs in the precise location you can change the pivot point by holding down the D key and then V
Drag the Pivot to the top right corner of the first face. Snap the face to the new location by holding down the V key.
Repeat the process on the other side to have the all UVs mapped as below.

Now, you have a dice perfectly textured with a single material!

UV Poly mapping (Bump Sign)
Open sign_bump_undone.ma

Select all the frontal faces of the diamond shape include the bottom face hidden in the rectangle. You can press 4 to view wireframe select that face.

In the Modeling section, in the menu bar, select UV > Planar > (Option box)
In the Option Window:
Fit Projection to - Bounding box
Project from - Z axis


After creating the planar mapping, you will see a manipulator (the bounding box), which allows you to move the UVs around the texture image.
Press 6 to show the texture to see the interactive changes when you play with the manipulator.
Use the handle and scale box to fit the bump sign to the diamond.

You can also move the manipulator in the UV Texture Editor.
Play around with the manipulator until the texture fit perfectly as below.

Select all the back face of the diamond including the faces of the border.
Create a Planar Mapping again, and fit the manipulator to the back metal texture as below (outer edge to the outer edge of the metal).

Now the edge UVs are overlapping, we have to unfold it.
Select only the back faces of the diamond (excluding the border).

In UV Texture Editor, Choose Select > Convert Selection to UVs.
Now, you have the UVs selected on the faces you had selected before.
Scale the UVs down to the inner edge of the border as below.

Repeat the process to the rectangle.

The back side of the rectangle

In Object mode, select the bolt on the diamond sign.
In UV texture Editor, choose Select > Convert Selection to UVs.

For the Bolt, you don't have to create a planar mapping, move and scale it to the bolt texture. Complete all 3 bolts.

Select the faces of the pole except the top and bottom faces.
In the Modeling section, in the menu bar, select UV > Cylindrical.
You will see the manipulator is different to the planar one. It is in a cylinder shape.
Zoom to the middle part of the manipulator.
Drag the scale handle to make a complete circle of cylindrical mapping.

Scale and move the manipulator in the UV Texture Editor to fit the UVs to the pole.

Select and create planar mapping to the top and bottom face of the pole separately.
Note: you should project from Y axis this time.

DONE!!

UV Poly mapping (Car)

Select the car body.
Open Windows >Modeling Editors > UV Editor.
From the menu bar select Image > UV Snapshot
Click Browse to locate the destination of the UV snapshot image.

Open you snapshot tiff in Photoshop.
Go to Channels, select Alpha 1, and click the icon Load channel as selection.
Go to layer, add a new layer and fill it with blue.
Delete Alpha 1.
Now, for the fun part. You can drag on the wireframe to draw anywhere on the car body.

Save your texture as a psd file, name it as Citroen_color.psd
Note: you should hide the wireframe layer when you save the psd, otherwise it will appear on the car body.
Back to Maya assign the texture to the car body material.

Every time you edit and saved the image in Photoshop, you should press the Reload under the attribute of the texture to update the image.

Note: The UV mapping is coorespond to any images assign to the material of the object. ie. color, bump or specular map share the same UV cooridinate. You can use one UV snapshot to create all different map.