Compaq 300 Developing OpenGL Applications on Alpha Platforms, Overlay Planes, Stencil Planes

Operation (Windows NT)

5.3.2.2.2 Overlay Planes

The PowerStorm 300 AGP graphics controller on the Intel platform provides hardware support for 2-bit double-buffered overlay planes. Note that for performance reasons, not all pixel formats support overlay planes. If you do not require overlay planes, selecting a pixel format without overlay support will ensure maximum performance. The availability of pixel formats with overlay planes can be disabled by using the Display Applet.

5.3.2.2.3 Stencil Planes

The PowerStorm display driver provides hardware support for a 4-bit stencil buffer. Note that for performance reasons, not all pixel formats support stencil planes. If you do not require stencil planes, selecting a pixel format without stencil planes will ensure maximum performance. The availability of pixel formats with stencil planes can be disabled by using the Display Applet.

5.3.2.2.4 SoftImage Customizations

When using the PowerStorm 300 AGP graphics controller on the Intel platform with Microsoft’s SoftImage, you should enable SoftImage Customizations using the Display Applet. In addition, you also need to enable 4-bit overlay using the Display Applet. Before starting Softimage, you need to make sure that the following environment variable is set:

SI_OVERLAY = USE_ONE_BIT

When SoftImage Customizations are enabled, other OpenGL applications may not behave correctly. Therefore it is recommended that SoftImage Customizations be disabled before running other OpenGL applications.

5.3.3 Developing OpenGL Applications on Alpha Platforms

This section provides information for developing OpenGL applications that optimize the performance of PowerStorm 300/350 PCI graphics controllers on Windows NT Alpha platforms. If you have a PowerStorm 300 AGP graphics controller on an Intel platform, see Section 5.3.2.

5.3.3.1 Pixel Format Support

The PowerStorm 300/350 PCI graphics controllers and display drivers for the Windows NT Alpha platform support a fully compliant implementation of OpenGL in combination with Windows NT OpenGL. Color index mode support is provided by the Windows NT generic OpenGL implementation, and thus is not hardware-accelerated.

The display driver on the PowerStorm 300 PCI graphics controller for the Windows NT Alpha platform supports the pixel formats listed in Table 5-5. The display driver on the PowerStorm 350 PCI graphics controller for the Windows NT Alpha platform supports the pixel formats listed in Table 5-6.

PowerStorm 300 AGP and 300/350 PCI Graphics Controllers 5–9