New Features

Texture Map Object

The new Texture Map object provides a simplified way of doing texture mapping at optimal performance. This object extends the texture mapping functionality provided in the Data Map Texture object in previous releases. As with the Data Map Texture object, the Texture Map object uses a raster image specified by the MipMap Texture object for the texture. Mapping a texture onto a surface can now be defined using the vertex, normal, or data fields of the polygon vertices. The Texture Map object provides sampling methods such as point, bilinear and trilinear to obtain texture values and provides several color composition techniques, such as blend, decal and modulate.

In a future release, the Texture Map object will replace the Data Map Texture object; at this release, however, the Data Map Texture object is retained to provide backward compatibility.

Pcache Object

The new Pcache object provides non-editable, non-hierarchical display list functionality for XGL. This object allows XGL programmers to tune XGL code for the high performance that display lists can provide. The use of a Pcache object can optimize performance for most 3D graphics applications running on graphics adaptors with display list capabilities.

CGM Functionality

CGM device functionality is now provided through the XGL Stream Device. The CGM device allows XGL to open and write to a Computer Graphics Metafile. In the XGL CGM implementation, stroke text, 3D circles, circular arcs, ellipses, elliptical arcs, and NURBs are output as polylines or polygons. Lines are interpolated, and surfaces are constant shaded. Although the XGL CGM Device outputs only 2D integer coordinates, all stages of the viewing pipeline are supported.

Transparent Overlay Support

Transparent overlays give applications the ability to superimpose images on the graphics in a display window. The XGL library provides support for transparent overlay windows, using the window system interface provided in the OpenWindows environment.

For detailed information on changes to the XGL library, see Appendix A, "Changes to the XGL Library".