Re: speed question

[Frank C <li...@si...>]

On 13-Jul-04, at 12:37 PM, Keith Wiley wrote:

> On Tue, 13 Jul 2004, Frank C wrote:
>
>> Actually, only pixmaps auto-generate mipmaps (this has long been a
>> source of confusion with QD3D).
>
>> Use pixmap textures and set the quality filter to mid or best and you
>> get instant mipmaps. Well if you're using the current CVS source at
>> least...
>
> So I can create the texture as a pixmap instead of a mipmap and it
> generates the lower res textures for me...or I can use a mipmap but I 
> have
> to create and supply the downsampled textures manually.  Are both 
> points
> made correct so far?

Yes and yes...

> If so, what is the advantage of mipmaps.  They require more work, so 
> what
> do they buy you?  Do they offer more control over when resolution is
> switched, or more gradations of texture dimension?  Any advantage at 
> all?

You can use your own halving algorithm if the built-in mipmap 
generation isn't to your liking (or too slow), or for debugging 
situations where you want to visualize exactly where the mips are 
switching. More importantly, mipmap texture objects let you create 
textures that don't use mipmapping at all by setting useMipmapping to 
false and only supplying the first mip level. This can save RAM for 
objects that are never minimized (like HUDs) or just in general when 
high quality filtering isn't important or desired.

To get back to the original topic of this post, I think your reasoning 
for wanting mipmapping may be flawed - it's probably faster to simply 
_not_ use mipmapping at all, at the cost of image quality.

Frank.