sign(a)

Graphics and GPU Programming Programming

Started by lomateron September 17, 2014 01:23 PM

3 comments, last by fastcall22 9 years, 7 months ago

lomateron

491

Author

September 17, 2014 01:23 PM

I just discovered that sign() is slow,and that it returns an int

So is there shorter faster code to do something like this?

float3 a;

if (a.x>0.0f){ a.x = 1.0f; } else{a.x = -1.0f;}

if (a.y>0.0f){ a.y = 1.0f; } else{a.y = -1.0f;}

if (a.z>0.0f){ a.z = 1.0f; } else{a.z = -1.0f;}

osmanb

2,082

September 17, 2014 01:35 PM

You can try doing: "a = (a > 0) * 2 - 1;" Depending on architecture, that may (or may not) be faster. (We use several different options, depending on platform, for example).

lomateron

491

Author

September 17, 2014 01:43 PM

So what are the other options?

osmanb

2,082

September 17, 2014 06:33 PM

Ah, sorry - in our actual scenario, we're operating on the Face semantic (or equivalent), which works differently on different platforms. There are some cases where it's already a bool, so we do less math. On all platforms where it's a float, we either use sign or the above math.