| memory for pixmaps: big vs many [message #54599] |
Thu, 21 June 2007 12:20 |
rclark
Messages: 12
Registered: September 1992
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Junior Member |
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In using offscreen pixmaps to preload a sequence of images for smooth
display in an animation you can run up against memory limitations in the
graphics hardware.
Two aproaches are to set up a very large pixmap that is
xsize*total_images by ysize and store the images along the x length
of the pixmap,
or
to set up total_images xsize by ysize pixmaps, one to an image.
The latter aproach gives your OS and graphics hardware more of a chance
to make use virtual memory. Works like a charm on my linux system while
the big pixmap movie loop hits the graphics card memory limit.
But a search through some discussion on the topic suggests that there
will likely be some OS and/or graphics card specific differences in
how well it works.
Does anyone have experience with this on multiple platforms and could
comment? For instance, any OS-wide generalizations that can be made,
or is it hopelessly graphics card dependent?
On a related note, the animation I'm interested in displaying is made
up of b&w images. So using an 8 bit rather than 24 bit mode should
make room for more images to be loaded in the card's memory.
Does using an 8 bit mode make room for 3x, 4x, or 1x times as many
images?
Richard Clark
rclark@lpl.arizona.edu
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