[jitter] normalize shader

On Oct 5, 2007, at 4:03 PM, Wesley Smith wrote:

> So here's the best I can think of:
>
> make a fragment shader that looks to the left of itself and above
> itself (and make sure you set border color to (0, 0, 0, 0).  At the
> location you're at, take the max of top and left and current and
> output the result.  This should produce the max values at the bottom
> right corner of the texture.  You can use that to normalize in another
> stage.

FWIW, this is not guaranteed, since fragments can be processed  
asynchronously in any order.

The only guaranteed fragment shader based implementation is to write  
an N pass shader, which folds the texture down in each step, taking  
the maximum value. N will be related to the logarithm of your image  
dimensions. The base on the logarithm will be the number of input  
samples you fold to each output sample. you will probably want to use  
the jit.gl.slab dimscale attribute to scale down the output but the  
same factor as your folding.

However, this might not be any faster than a CPU based implementation.

-Joshua