Is there a way to specify which mip levels of a texture the driver should keep in VRAM and which not?I need to texture a large terrain so I want to be able to page in/out mip levels as needed to have texture detail only where it counts and keep the textures resident.Is this possible?
as mip maps are stored in the texture object wiht the main texture ide persume that if the main texture isnt in the vid mem then the mips aint.
There is also an extension for specifying which mipmaps you want created (up to what level) but I forgot the name. I think it was an SGI extension.
V-man
Sorry for taking so long to reply but I’m having trouble with my monitor…
Anyway I need a way to keep the texture object in video memory and some of its mipmap levels out.The texture lod extensions wich is the one I assume you mean V-Man lets you specify wich levels to use not which ones to actually store in video memory.At least that’s what the spec says.
On some cards, mipmaps can be loaded into video memory as they are required, rather than loading all levels at once (e.g. http://www.3dlabs.com/product/technology/pdf/vtpaper.pdf)..) I don’t know if, say, the GeForce3 is such a card, though.
If your card can do this, you can implicitly “page out” mipmap levels by controlling GL_TEXTURE_BASE_LEVEL and GL_TEXTURE_MAX_LEVEL. You still can’t explicitly decide which mipmaps to page in or out, but mipmaps that aren’t used anymore will get paged out automatically.
– Tom
I don’t like to use vendor-specific extensions but I assume that the TEXTURE_LOD extension is implemented most opengl implementations.Still, are you sure about the fact that the driver pages on a mipmap level and not on a texture level.This means: are you sure that(most) drivers will page in/out individual mipmaps?I believe a driver developer(for nvidia) said in a previous thread of mine that these parameters could in theory control which levels to keep in memory but do not do so.
btw I believe that the GL_TEXTURE_BASE_LEVEL and GL_TEXTURE_MAX_LEVEL parameters are part of the opengl specification.Is that true or is checking for the SGIS_TEXTURE_LOD extension still required.
I think that I need to start a more specific thread on this.
These aren’t vendor specific, but Matt from NVIDIA has already told us that these tokens are not used to determine residency of MIP levels on NVIDIA, right after telling us how wonderful the NVIDIA texture memory manager was.
Yes Dorbie,that was the driver developer I was reffering to.So I guess the answer to my initial question is no.