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ASUS 3DP-V500TX
B. OPENGL ENVIRONMENT
OpenGL Overlay Planes Support
Introduction
Overlay planes provide a method by which OpenGL applications can render over
screen areas in a nondestructive way. A typical use of such functionality would be to
draw dialog boxes above a rendered 3d scene. There would be no need to save and
restore from a bitmap or re-render the scene when the dialog is cleared as the stan-
dard, main-plane, rendering remains intact. Overlay planes are used by many high
end OpenGL applications as they are a common feature on Silicon Graphics hard-
ware.
Overlay planes are not provided as a standard part of OpenGL in the way that stencil
or depth buffers are. On Windows NT Microsoft define a standard overlay plane
specification as part of the WGL interface. This interface is used by Windows NT
OpenGL applications which require overlay functionality, notably Softimage.
Implementation
The Microsoft overlays standard provides for up to 15 levels of underlay and 15
levels of overlay in addition to the main rendering plane. Each level of underlay or
overlay, referred to as a layer plane, has it own layer plane descriptor structure.
OpenGL Registry Variables
OpenGL.SupportSoftimage: This variable is used to optimise the OpenGL driv-
ers for use with version 3.01 of the SoftImage rendering package. We do not recom-
mend use of this variable unless you will be using the SoftImage application. If this
variable is defined and set to 1 then the optimizations will be enabled.
A system reboot is necessary for changes in this variable to take effect.
OpenGL.SupportSoftimage351: This variable will optimise the drivers for ver-
sion 3.51 of the SoftImage rendering package. Once again we recommend that you
only use this variable when using Softimage. If this variable is defined and set to 1
then the optimization will be enabled.
A system reboot is necessary for changes in this variable to take effect.
Miscellaneous Registry Variables
UseSoftwareCursor: If defined and set to 1 a software cursor is used instead of the
normal hardware cursor. This variable is not created by default.
A system reboot is necessary for changes in this variable to take effect.
B. OPENGL
ENV
.
Registry V
ariables
