Quote - Most nodes don't increase memory use. An ImageMap node does, because it holds the entire image. Any math you do on the image does not generate new images. Instead, each point is calculated on the fly and then discarded when no longer needed. So a purely procedural texture (using no ImageMap nodes) is always going to take up less system memory.

Are you certain?  How did you come to know that?  I don't think that's very likely.  As you reposition a camera, the graphics engine would have to regenerate the entire bitmap from scratch for every increment of the camera, or I expect any change in lighting.  From a programmer's perspective I certainly wouldn't do it that way, I think it'd be stupid.  Granted, the preview bitmap can be much smaller than the rendered bitmap, but that's still a ton of wasted cycles that you need for other things, like moving the polygons themselves around.

Quote - Video memory is irrelevent except for the preview in P7. The renderer is purely software - you don't even need a 3D graphics card to do software rendering.

True enough, but it may matter a great deal when the scene has many bitmaps to preview and the graphics card has a small amount of memory (e.g. some dinky old card with 32mb).  If there's enough texture data (and depending on how the card works, this may be shared with 3d data) then the card may be unable to display the preview.  I think it's kind of a moot point in respect to this question, since I'm pretty sure both situations would use equal video memory.

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