Leaving textures in memory, good or bad? 2004-03-05 - By NoiseCrime
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-- -- Original Message -- --
From: "Barry Swan" <gerbil@(protected)>
To: <dir3d-l@(protected)>
Sent: Thursday, March 04, 2004 8:42 PM
Subject: [Dir3d-l] Leaving textures in memory, good or bad?
Memory usage of textures, my take on it.
1. Cast member
You gotta get you texture from somewhere, and most of the time it will be a
cast member. So Director most load and decompress the bitmap into standard
ram . It will remain there until you unload it, or Directors own
housekeeping detects its no longer in use.
2. Texture
When you create a texture SW3D will store a bitmap version into main ram,
this will be compressed if you set the texture to have compression. Then
this bitmap is uploaded to the API (not card) as a texture to the properties
you've set in the texture palette entry (renderformat and renderquality (i.e
mipmaps)) If it has mipmaps these will be created and also uploaded.
However there is no gaurantee at this stage that the texture will be placed
in the cards vram, thats entirely up to the API to decide, you have no
control over it. If its not on the card then its going to be in your main
memory.
So in terms of memory a single texture can actually use quite a bit. First
there is the bitmap in Directors cast, then there is the stored bitmap for
sw3d, that allows you to switch renderformat/qauilty on the fly, and
finallly the version that is 'meant' to be on the card, but might not be
(which also might have mipmaps).
First its clear that the director copy of the bitmap is usually surpluss to
requirements, and so once its been loaded as a texture the member may be
deleted, unloaded or ignored (allow Director to sort it out).
Secondly you'll have two copies of the texture, the bitmap (compressed)
version and the actual texture version. The first will remain in main memory
until it is deleted from sw3d,the second may be on the card or in main
memory and is used by the API, including mipmaps. Again this version remains
until deleted from sw3d.
In the main there is no need to delete these versions, unless you no longer
need them. If you do a resetworld() between levels of a game or something
they will automatically be deleted anyway. The only possible reason is if
you need to display many large textures and would run out of main memory
unless you deleted ones that were no longer in use. I thinking here if
you're doing a slide show with 2048x2048 textures or something, where its
clear you'd want to delete old ones from memory.
Hope this helps.
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