Jus Wonderin

J.Melo · 4th July 2007, 05:31

Is there any difference between atan(a/b) and atan2(a,b)?

Grandchild · 7th July 2007, 11:39

i think it's faster because it's implemented so it doesn't have to translate the 'a/b' from avs-code to "computer-code" anymore.
but the difference will be hardly noticeable if you don't use it in the pixelbox with, say, n=5000 so it'll be executed 5000 times per frame.

gc

J.Melo · 7th July 2007, 15:02

Ok, so It's just a bit faster then?

Edit: I just tested it and I got 120+-5 fps for atan and only 90+-5 fps for atan2.

???

Why would there be an atan2 function then? Try it on your PC. Maybe it varies between processors, or somthin. Use this preset. Just change the atan func. to atan2.

J.Melo · 7th July 2007, 15:17

I had to post a new reply because apparently you cant attatch a file while editing

Grandchild · 9th July 2007, 04:58

it seems you're right... strange.

but now i remember that in pak-9's programming tutorial he says that atan2 comes with some additional features like avoiding division by zero and some wrapping around the "ends" of a circle [you know, between r=0 and r=2*$PI]
/looks into the guide
hm can't find it now, maybe he told me on irc one time, i don't know.
when i use atan instead of atan2 in a movement there are some glitches to be found but they really are minor. and there's a small dot in the middle of the screen. plus it's slightly slower than atan2.
so i think it might actually be sometimes faster to use atan(a/b) than atan2(a,b) in an ssc but i'll stick to atan2 in movements.

but have a look [it's all in the movement]:

J.Melo · 9th July 2007, 09:47

I see what you mean. The edges look so much smoother in atan2, and there is no dot in the middle. I did get about 3 fps faster in atan2 also.

shreyas_potnis · 11th July 2007, 12:33

atan2 returns the correct angle that the vector (a,b) makes with the x-axis....atan(b/a) returns, well just that.
like atan((-3)/4) and atan(4/(-3)) will be the same but atan2 wont be.

J.Melo · 11th July 2007, 16:23

atan((-3)/4) and atan(4/(-3)) are different. The thing is, atan(4/-3) and atan2(4,-3) are not the same. I found something in an AVS preset. Anyone wanna process it and explain?

4th July 2007, 05:31	#1
J.Melo Senior Member Join Date: Oct 2006 Posts: 328	Jus Wonderin Is there any difference between atan(a/b) and atan2(a,b)?

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7th July 2007, 11:39	#2
Grandchild Senior Member Join Date: Oct 2005 Location: Germany Posts: 324	i think it's faster because it's implemented so it doesn't have to translate the 'a/b' from avs-code to "computer-code" anymore. but the difference will be hardly noticeable if you don't use it in the pixelbox with, say, n=5000 so it'll be executed 5000 times per frame. gc

7th July 2007, 15:02	#3
J.Melo Senior Member Join Date: Oct 2006 Posts: 328	Ok, so It's just a bit faster then? Edit: I just tested it and I got 120+-5 fps for atan and only 90+-5 fps for atan2. ??? Why would there be an atan2 function then? Try it on your PC. Maybe it varies between processors, or somthin. Use this preset. Just change the atan func. to atan2.

9th July 2007, 09:47	#6
J.Melo Senior Member Join Date: Oct 2006 Posts: 328	I see what you mean. The edges look so much smoother in atan2, and there is no dot in the middle. I did get about 3 fps faster in atan2 also.

11th July 2007, 12:33	#7
shreyas_potnis Major Dude Join Date: Jan 2003 Location: Mumbai, India Posts: 787	atan2 returns the correct angle that the vector (a,b) makes with the x-axis....atan(b/a) returns, well just that. like atan((-3)/4) and atan(4/(-3)) will be the same but atan2 wont be.