Programming with QuickTime VR

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QTVRGetBackBufferSettings

You can use the QTVRGetBackBufferSettings function to get information about the resolution, depth, and size of the back buffer maintained internally by QuickTime VR for caching a panoramic image in a particular pixel format.

OSErr QTVRGetBackBufferSettings (
                     QTVRInstance qtvr,
                     UInt16 *resolution,
                     UInt32 *cachePixelFormat,
                     SInt16 *cacheSize);
qtvr
An instance of a QuickTime VR movie.
resolution
On entry, a pointer to an unsigned short integer. On exit, that integer is set to the index of the current image resolution. See "Resolutions" for a description of the available resolutions.
cachePixelFormat
On entry, a pointer to a long integer. On exit, that long integer is set to the pixel format of the current panorama back buffer. See "Pixel Formats" for more information.
cacheSize
On entry, a pointer to a short integer. On exit, that integer is set to a value that describes the size of the current panorama back buffer. See "Cache Sizes" .
function result
A result code.

DESCRIPTION

The QTVRGetBackBufferSettings function returns, through the resolution parameter, the index of the current resolution for the QuickTime VR movie specified by the qtvr parameter. The index indicates which bit in the mask value returned by QTVRGetAvailableResolutions specifies the current resolution. For example, if the returned index is 1, the base resolution is being used. If the returned index is 2, then a resolution of half the base resolution is being used.

QTVRGetBackBufferSettings also returns the pixel format and the cache size in the cachePixelFormat and cacheSize parameters, respectively.

SPECIAL CONSIDERATIONS

QTVRGetBackBufferSettings is valid only for panoramic nodes.

SEE ALSO

Use QTVRSetBackBufferPrefs (next) to set the resolution, cache depth, and cache size of the panorama back buffer maintained internally by QuickTime VR for caching an image. Use QTVRGetAvailableResolutions [link] to determine which resolutions are supported by a node. Use QTVRGetBackBufferMemInfo [link] to determine the memory requirements for the preferred settings.

© 1997 Apple Computer, Inc.

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