Re: [Algorithms] Blurring in HLSL

[Mark S. <ma...@4c...>]

Ivan-Assen Ivanov wrote:
>> Second, you can calculate the Gaussian blur in a single post-processing
>> pass if you want. It's no different from doing the horizontal and
>> vertical in two different passes, except for the amount of math
>> involved. If you do that, then you'll be using a large amount of pixel
>> shader instructions compared to framebuffer writes, which will generally
>> be slower than just doing two separate passes on render targets. All
>> hardware is decent enough at fill rate compared to shader instructions
>> that it doesn't make sense to try to do it in a single post-process
>> pass. When we get a 1000:1 ratio of shader ops:framebuffer writes, that
>> detemrination may change, but we're nowhere near there just yet :-)
>>     
>
> I beg to disagree - it still depends on the particular hardware and
> filter sizes.
>
> There's this weird piece of hardware that has
> sold in the mid-two-digit millions, yet refuses to sample from its framebuffer,
> so if you're doing two passes, you have to do transfer the results from the
> first pass into RAM, and 5x5 and 9x9 Gaussian kernels turn out faster
> in one pass instead of separated in H and V.
>
>   
I'm curious, what hardware is that? This is the first I've heard of this 
and I'm wondering if it's something I'd need to worry about.