Re: [Algorithms] Texture mip streaming prioritization

[Manuel M. <m.m...@wa...>]

Hi Josh,

> I'm currently working on a texture streaming system and looking into ways
> to prioritize which mips on which textures should be loaded.
> I was hoping that people on this list may have experience with these
> algorithms that they could share?
> 
> Currently I know which mips need to be loaded in order to render a scene
> without degradation in image quality.
> I would now like to apply a memory budget to textures, and make decisions
> about which mips of which textures should be loaded over others.
> 
> My current line of thinking involves comparing cost / benefit of loading
> each individual mip.
> i.e.
> 
> How many pixels would be affected by a particular mip level being loaded
> versus how much memory would that mip level use?
> 
> This becomes Priority = Benefit / Cost
> 
> I'd then sort for highest priority and assign memory budget to those mips
> at the top of the list.
> 
> Any thoughts? comments? Alternatives that work better? Alternatives that
> have worked enough?
> 
> Problems that arise with the above algorithm are quite broad, and in
> particular, optimising the tipping point between cost and benifit would be
> necessary. Also, calculating the number of pixels affected would involve
> crude calculations that aren't really going to affect real world values....

I think it might boil down to the question if it is possible to implement
efficient histograms on the GPU (e.g. via 
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.70.40), keyed
on mip-map level and texture ID. Doing a low-res histogram pass should give
you a very good indication on the number of affected pixels.

cheers,

	Manuel