Basic HTML version of Foils prepared April 6 1997

Foil 158 Texture Mapping with S and T

From VRML 2 Basic Concepts and Definitions CPS616 -- Information Track of CPS -- Spring Semester 97. by Zeynep Ozdemir(Geoffrey C. Fox)


With image textures, it is considered that it has a 2-D graph and x axis is called S axis and y axis is called as T axis.
Texture image always extends from 0.0 to 1.0 in the S (x) direction and from 0.0 to 1.0 in the T (y) direction in the texture coordinate system.
TextureCoordinate only has a point field and specifies a list of texture coordinates and may be used as the value of the texCoord field in the IndexedFaceSet and ElevationGrid nodes.
  • This is "pointed to" by texCoordIndex field
It is possible to give a point in a TextureCoordinate node which is outside of the texture image such as beyond the left, right, bottom, or top edges of the image.
  • When wrapping (repeatS/repeatT) is allowed, coordinates above the top of the image wrap to the bottom of the image, and coordinates below the bottom edge wrap back to the top, and so on.
When wrapping is not in use, it is called clamping. This mode is useful to make sure that a texture image occurs just once. Clamping restricts the texture images in the S, T, or both directions to lie in range 0 to 1.
repeatS and repeatT fields of texture nodes specifies whether wrapping is on or off in the corresponding Coordinate.



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