UV Tag

The UV Tag extends polygon objects with editable UV coordinates. These coordinates are needed to texture objects. You can only add a UV Tag to polygon objects.

Attention: The UV Tag tells Cheetah3D to export UV coordinates in the various 3D file exporters. Every object which should export UV coords must have a UV Tag even if you only use its natural UV coords.

The UV Tag is initially one of the most confusing parts of Cheetah3D because it is both a tool and a tag. However, once you get used to it, you will find that it is quite handy. To properly use the UV Tag you have to understand how it works internally. There are three families of object on which the UV Tag behaves, each with different results.

  1. Parametric polygon objects
    When you add a UV Tag to a parametric polygon object, the natural UV coordinates of this object will be used if you set the mapping type to "UV-mapping". Every parametric polygon object has one set of natural UV coordinates, but if the natural UV coordinates don't fulfil your needs, then you can use the other mapping types which are available in Cheetah3D. The mapping types then overwrite the natural UV coordinates of the parametric polygon object.
  2. Raw Polygonobject
    Raw Polygonobjects don't have natural UV coordinates, so you have to assign the UV coords to these objects manually. With raw polygon objects it is also possible to map UV coords to single polygon selections. See Example 2 to learn how to assign UV coordinates to polygon selections.
    Also take care to read about the save property below.
  3. Creator objects
    Creator object also have natural UV coords but they normally inherit them from the child objects which build up the creator object. The child object therefore needs a correctly assigned UV Tag so that the creator object can calculate the natural UV coords. The other behaviour is like in parametric objects.

Properties

  • position: Position of the texture mapping geometry. The position can also be modified with the move tool when the UV Tag is selected.
  • rotation: Rotation of the texture mapping geometry. The rotation can also be modified with the rotate tool when the UV Tag is selected.
  • scale: Scale of the texture mapping geometry. The scale can also be modified with the scale tool when the UV Tag is selected.
  • adapt scale: Sets the scale of the UV Tag to the size of the bounding box of the tags owner.
  • mapping type:
    • UV: Three behaviors:
      • If the tag is assigned to a parametric polygon object, the natural UV coordinates will be calculated.
      • If the tag is assigned to a creator object, the UV coordinates will be inherited from the children.
      • If the tag is assigned to a raw polygon object, the saved UV coordinates will be used.
    • spherical: Spherical texture mapping geometry.
    • cubic: Cubic texture mapping geometry.
    • flat: Flat texture mapping geometry.
    • cylindrical: Cylindrical texture mapping geometry.
    • frontal: UV mapping via the screen space
  • map: Determines if UV coordinates should be assigned to all polygons or only to the selected polygons.
  • offset U: Add an offset to the U coordinate.
  • offset V: Add an offset to the V coordinate.
  • scale U: Multiply the U coordinate.
  • scale V: Multiply the V coordinate.
  • save: The save button is only needed when you map UV coords to raw polygon objects. If you use another mapping type than "UV-mapping" the UV coords will only be calculated on the fly for the 3D preview and won't be written into the UV Tag. To write the coords into the UV Tag you have to press the save button. Once this is done, the newly assigned UV coords will also be available for the creator objects and can also be exported to files.
    The advantage of this approach is that you often have models which already have UV coords. For example, when you make a Parametric object editable, you can then adjust the UV coords without damaging anything. You have to press the save button before the new UV coords will be stored in the UV Tag. If you messed up your UV coords you just have to set the mapping type back to UV-mapping and you get back your last saved state.

Example 1
Assign UV coordinates to parametric polygon objects:

  • Select the object.
  • Add the UV Tag.
  • Select the mapping type. And eventually position the mapping geometry.
  • You're finished!

Example 2
Assign UV coordinates to a polygon selection

  1. Select a raw polygon object.
  2. Add the UV Tag.
  3. Switch into polygon mode.
  4. Set the UV Tag property map to selection.
  5. Select the polygons to which you want to assign UV coordinates.
  6. Select the mapping type in the UV Tag properties.
  7. Position the mapping geometry with the transform tool. The UV Tag must be selected to see the mapping geometry.
  8. When you are finished press the save button. Now the new UV coords will be written into the UV Tag.
  9. Continue with step 5 until you have assigned UV coords to all polygons.

© 2001-2010 Martin Wengenmayer. All rights reserved.