RE: GLSL pow() Function on ATI and NVIDIA GPUs

Subject: RE: GLSL pow() Function on ATI and NVIDIA GPUs

From: Memo Akten <email@hidden>

Date: Thu, 10 Apr 2008 09:11:17 +0100

Delivered-to: email@hidden

Hi Alex, its strange that they don't work the same...

pow(x, -n) is mathematically the same as 1/pow(x, n).

So if you know that n is less than zero you can always do:

1.0/pow(x, -n); // note that by writing -n its effectively making it positive, probably faster than doing abs.

if you aren't sure whether n is less than zero or not you can always do:

n>0 ? pow(x, n) : 1.0/pow(x, -n);

hope that solves your problem!

Memo (Mehmet S. Akten)

www.memo.tv

On Apr 9, 2008, at 6:42 PM, Alex Drinkwater wrote:

> This is probably way off topic, but...

> has anyone noticed differences between the way the GLSL pow() function works on the two graphics card types? It appears that if you pass a number less than 0 as either of the parameters of the pow() function, on an ATI/Radeon-equipped machine you get a number, while on a machine with an NVIDIA/GeForce card, you get 'undefined'. I wonder if anyone happens to know how I can mimic the result from the ATI card on the NVIDIA GPUs?

> A long-shot, I know...

> alx

> http://machinesdontcare.wordpress.com

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