UV mapping research

Planar UV mapping

Planar mapping projects UVs onto a mesh through a plane. This projection is best for objects that are relatively flat, or at least are completely visible from one camera angle.

Planar mapping typically gives overlapping UV shells. The UV shells may be perfectly superimposed and look like a single UV shell. You should use UV > Layout after mapping to separate overlapping UVs.

The Best Plane Texturing Tool assigns UVs to the faces you select based on a plane computed from vertices you specify.

You can select the faces you want to map before you choose the Best Plane Texturing tool, or you can choose the tool and then click each face you want to map.

To map based on the best fit plane of the selection

1. Select the faces you want to map UVs onto.
2. Select UV > Best Plane Texturing Tool.
3. You click faces to add them to the selection.
4. Select one or more faces on which you want to map the texture. You cannot marquee-select the faces—you must select the faces one by one, or select the faces before using the operation.
5. Press Enter.
6. Select one or more vertices (press the right mouse button on the mesh and choose Vertex to switch to selecting vertices).
7. Press Enter.
8. Use the UV Editor to view and edit the resulting UVs.
   

To project from a plane defined by the view

1. Select the faces you want to project UVs onto.
2. Tumble the perspective view, or track an orthographic view to look at the faces.
3. Select UV > Camera-Based.
   

To map based on a planar projection

1. Select the faces you want to project UVs onto.
2. Select UV > Planar > .
   The Planar Mapping Options window appears.
3. Set the following options as required:
   • Click Best Plane to position the manipulator based on the faces you selected.
   • Click Bounding Box to position the manipulator based on the bounding box of the mesh.
4. Click Project.
5. Use the projection manipulator to control how the plane distributes UVs.
6. Use the UV Editor to view and edit the resulting UVs.
   
   You can also rotate the manipulator by clicking the red crossed lines, which reveals the Show Manipulator tool. Click the light blue circle around the Show Manipulator handle to activate the rotate handles.

Notes

• Planar mapping can create shared, overlapping UVs that can look like texture borders. Turn on texture border display (in Display > Polygons > Texture Border Edges) to clearly show texture borders.
• Shared, overlapping UVs can create seam problems if you paint over them with the 3D Paint or Paint Fur Attributes Tools.
  To avoid these problems, manually separate the UVs with UV > Layout > . Set Separate shells to Folds and the Shell layout option to Along U or Into Square.
• Projection mapping only works properly on a single object at a time. If you need to apply a projection to multiple polygonal objects in a single step, combine the objects into one, apply the projection, and then separate the parts back out. Otherwise, perform a projection on each object separately.
• When a model’s form is very organic, and you require a complete UV representation of that model for texture mapping, a planar projection can produce UVs that overlap and appear distorted. Unless you want this to occur it is recommended you try another UV mapping technique.
  

Cylindrical UV mapping

Cylindrical mapping creates UVs for an object based on a cylindrical projection shape that gets wrapped around the mesh. This projection is best for shapes which can be completely enclosed and visible within a cylinder, without projecting or hollow parts.

1. Select the faces you want to project UVs onto.
2. Select UV > Cylindrical Mapping.
3. Use the manipulator to change the position and size of the projection shape.
4. Use the UV Editor to view and edit the resulting UVs.
   
   Note:
   

   Projection mapping only works properly on a single object at a time. If you need to apply a projection to multiple polygonal objects in a single step, combine the objects into one, apply the projection, and then separate the parts back out. Otherwise, perform a projection on each object separately.
   

Spherical UV mapping

Spherical mapping create UVs using a projection that is based on a spherical shape wrapped around the mesh. This projection is best for shapes which can be completely enclosed and visible within a sphere, without projecting or hollow parts.

To create UVs using a spherical mapping technique

1. Select the faces you want to project UVs onto.
2. Select UV > Spherical Mapping.
3. Use the manipulator to change the position and size of the projection shape.
4. Use the UV Editor to view and edit the resulting UVs.
   
   Note:
   

   Projection mapping only works properly on a single object at a time. If you need to apply a projection to multiple polygonal objects in a single step, combine the objects into one, apply the projection, and then separate the parts back out. Otherwise, perform a projection on each object separately.

Automatic UV mapping

Automatic mapping creates UVs for a polygon mesh by attempting to find the best UV placement by simultaneously projecting from multiple planes. This method of UV mapping is useful on more complex shapes where the basic planar, cylindrical, or spherical projections do not produce UVs that are useful, especially on components that project outwards or are hollow in nature.

Automatic mapping creates several UV map pieces or shells in texture space. This is fine if you are using tools that deal with UVs automatically for you, such as standard (not combed) fur and the 3D Paint tool in projection mode. If you need to work with the UVs manually, you will need to stitch the UV shells back together in the UV Editor using the Move and Sew UV Edges feature.

You can also specify user-defined planes for the projection of UV texture coordinates. The Load Projection option uses a polygon object you specify from the current scene.

To facilitate more accurate UV projections a projection manipulator is displayed when using the Automatic Mapping feature. The projection manipulator lets you correlate the multiple planar UV projections that occur in the scene view with how the resulting UVs appear in the UV Editor.

The projection manipulator appears centered about the selected object in the scene view with blue planes that correspond to the number of planes set by the Automatic Mapping’s Planes option. A light blue color indicates that the projection plane is oriented facing away from the selected object, while a dark blue plane indicates the side of the projection plane that is oriented facing towards the selected object.

The manipulator’s planes are displayed semi-transparent at a scale of 50% of the actual projection plane so they don’t fully occlude the object when using the manipulator. Red and green lines appear along the edge of each plane to indicate the corresponding U and V axes within the UV Editor.

You can move, rotate, and scale the UV projection manipulator just like other manipulators in Maya. Scaling the manipulator affects the resulting scale of the projected UVs in the UV Editor.

You can reset any transformations for the projection manipulator using the Channel Box. When a custom projection object is specified using the Load Projection option, the projection manipulator gets updated to reflect the planes specified by the custom projection.

To map UVs for a polygon object using Automatic Mapping

1. Select a polygon object in the scene view that you want to project UVs texture coordinates.
2. Select UV > UV Editor to display the UV Editor or select the Persp/UV Texture Editor layout shortcut from the Toolbar to view the perspective view and the UV Editor side by side.
   When you project the UVs they will appear in the UV Editor’s 2D view.
3. From the Polygons menu set, select UV > Automatic > .
   The Polygon Automatic Mapping Options window appears.
4. Set the following options depending on your requirements:
   • Set the Planes setting to the desired number of projections you require and click Project. (The more planes you use, the less distortion in the UV layout but the more shells are created).
   The automatic mapping projection manipulator appears centered about the object in the scene view with blue projection planes that correspond to the Planes setting you specified. That is, if the Planes option was set to 4, then 4 planes appear on the manipulator.
5. To move, rotate, or scale the projection manipulator do the following:
   • To move the projection manipulator in X, Y, Z, drag any of the three colored arrow handles while moving your mouse.
   • To rotate the projection manipulator, click the light blue circular rotate handle to make the X, Y, Z rotate handles appear. Dragging any of the three circles rotates the manipulator about X, Y, or Z.
   • To non-proportionally scale the projection manipulator, drag any of the three colored box handles on the manipulator.
   • To uniformly scale the projection manipulator, click any of the three box handles on the tip of the manipulator so a 3D box appears. Drag the box to scale the manipulator uniformly.
6. Use the UV Editor to view and edit the resulting UVs.
   Note:
   

   Projection mapping only works properly on a single object at a time. If you need to apply a projection to multiple polygonal objects in a single step, combine the objects into one, apply the projection, and then separate the parts again Otherwise, perform a projection on each object separately.

User-defined UV mapping

You can map UV texture coordinates by specifying user-defined planes for UV projection using the Load Projection option within the Automatic Mapping feature.

The Load Projection option uses a polygon object that you specify from the current Maya scene. The object can form a cage around the object or be comprised of separate faces that intersect each other at its center. TheAutomatic Mapping projection manipulator updates when a user-defined object is specified for projection.

Criteria for user-defined projection objects

• The object used as a user-defined projection object must have UV texture coordinates.
• It is recommended that the projection object be comprised of separated polygon faces. That is, a polygon primitive that gets used as a projection object should first be separated into separate meshes using Edit Mesh > Extract. (NURBS and subdivision surfaces are not valid surface types for use with Load Projection.)

In addition, it is useful to know that:

• The UVs of the projection object determine the shape and location of the final projection mapping that occurs.
• You can translate any face from the Load Projection object along its normal with no affect on the resulting projection.
• Scaling or rotating any face from the Load Projection object will affect the resulting orientation and scale of the final UV projection. The projection manipulator updates when this occurs.
• The maximum number of polygon faces that can be specified for a projection object is 31.

To load a user-defined polygon object for use with Automatic Mapping

1. Select a polygon object in the scene view that you want to project UVs onto.
2. Select UV > UV Editor to open the UV Editor.
   The existing UVs for the object appear in the UV Editor’s 2D view.
3. From the Polygons menu set, select UV > Automatic > .
   The Polygon Automatic Mapping Options window appears.
4. In the Polygon Automatic Mapping Options window, turn on the Load Projection option, then do one of the following:
   • Specify the object in your current scene you want to have loaded as the projection object by typing its name in the Projection Object box.
   • Select the object in your current scene that you want to have loaded as the projection object, and then click Load Selected. The name of the object appears in the Projection Object box. See Criteria for user-defined projection objects above.
5. Click Project or Apply to execute the Automatic Mapping feature.
   The automatic mapping projection manipulator appears centered about the object in the scene view with blue projection planes that correspond in orientation to the planes of the Load Projection object you specified. That is, if the Load Projection object has 8 planes in various angles of orientation, the projection manipulator displays similarly.
   Note: In some instances, the Load Projection object may cause the planes on the automatic mapping projection manipulator to appear unexpectedly offset or skewed from the object you’re projecting on. This UV offset is based on the original UVs for the Load Projection object and doesn’t affect the quality of the projection.
   

   You can unitize the UVs for the Load Projection object prior to projection so its UVs reside in the 0 to 1 texture space. While this will make the projection manipulator appear more centered about the polygon object it may not provide the UV mapping results you were expecting as the UVs will be projected similar to having explicitly specified the Overlap feature.
6. Translate, rotate, or scale the manipulator as required to achieve the UV projections you require. The projected UVs appear in the UV Editor. You can observe them update within the UV Editor whenever the manipulator is moved within the scene view.

Confirm UV placement

Confirming that UVs are positioned correctly for a surface mesh is critical if you want the textures to appear correctly on the surfaces of your mesh. One method of confirming the UV placement is to assign a shader that contains a texture with visual characteristics that help indicate how the UVs are mapping the texture onto the surface.

When you turn on UV > Assign Shader, Maya will assign a checkerboard texture shader to the mesh as you project UVs. This provides a quick visual indication of the UV placement.

You can use a different texture on the defaultPolygonShader. For example, if you’re going to be mapping a stone texture to many objects, edit the defaultPolygonShader to use a stone texture for previewing.

You can also create your own custom 2D image using a paint or 2D image manipulation application.

If you do not need to pre-adjust your texture maps, turn off Assign Shader to Each Projection. The option is off by default.

Transfer UVs between meshes

You can map your UVs to a smoothed version of your polygon model, where it may be easier to get good UVs (for example, you can smooth out wrinkles which cause overlapping UVs). Then you can use the Transfer operation to copy the mapped UVs back onto the complex original model.

To transfer smoothed UVs between polygon meshes

1. Duplicate your polygon mesh.
2. On the duplicate, select the vertices you want to smooth.
3. Select Edit Mesh > Average Vertices > .
4. In the Average Vertices Options that appear, set the Smoothing amount then click Apply.
   Note: Increase the Smoothing amount value to smooth the selection quickly. You can also click Apply repeatedly to smooth repeatedly.
5. Project UVs onto the smoothed duplicate model using any of the mapping options in the Create UVs menu.
6. Use Mesh > Transfer Attributes to copy the UVs from the smoothed duplicated back to the original mesh.

All information obtained from - (Help.autodesk.com)