RE: [Algorithms] Hash function and cache implementation

[Marcelo A. C. <ca...@es...>]

> Maybe a quick crc32/16?
> Or... The sum of the first 3 pixels%something?

Two options worth trying. I will do some reserch on CRC. Never played
with it so it may be a good opportunity to learn more about the subject.
The second option seems to offer the best cost to beneffit ratio,
though.

--camelo


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> -----Original Message-----
> From: gda...@li...
> [mailto:gda...@li...] On 
> Behalf Of Marcelo A. Camelo
> Sent: Tuesday, July 01, 2003 4:41 PM
> To: gda...@li...
> Subject: [Algorithms] Hash function and cache implementation
> 
> 
> Hi!!!
> 
> I'm about to implement a cache for my terrain textures and I could use

> some help on choosing an appropriate data container and hash function 
> for cache look-up.
> 
> Some specific information about the problem:
> 
> I'm working on a terrain engine that uses textures much like warcraft 
> III, using tiny tiled textures (32x32 pixels) at the quads level. Each

> tile is built on-the-fly, using the texture type information stored on

> each of its four vertices (yielding c_tile_types_count^4 individual 
> tile textures).
> 
> To speed-up rendering, I group tiles in patches of size 8x8,
> as they are
> needed (rendering them to a new texture). This texture is 
> what I want to
> cache.
> 
> The key to my cache should be derived from the tile data in
> each vertex
> used to render the texture, plus the desired level of detail. The tile
> data is an array of unsigned chars [of dimension 
> (c_patch_size + 1)^2],
> although each entry is usually in the range [0,3] ([0,7] in the worst
> case). The LOD is also a char within those ranges. Any ideas on a hash
> function I can use?
> 
> If I were not limited to the MSVC6 stl, hash_map would be my first 
> option for the cache container but, unfortunately, I'm stuck to it. 
> I've found an stand alone implementation of the hash_map container 
> called my_hash_map
> (http://www.csua.berkeley.edu/~emin/source_code/hash_map/index.html)
> which I'll be evaluating. May save me some time. Any 
> suggestions on this
> area?
> 
> --camelo
> 
> 
> 
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