POV-Ray : Newsgroups : povray.general : Stupid math help Server Time: 22 Oct 2017 21:06:54 GMT
 Stupid math help (Message 1 to 3 of 3)
 From: Mike Horvath Subject: Stupid math help Date: 10 Nov 2016 18:10:00 Message: <5824b7f8\$1@news.povray.org>
```I have this formula from Wikipedia:

[itex]A_v = [/itex] [itex]\log_2[/itex] [itex]A^2[/itex]

How do I use this in POV-Ray? What is the correct syntax? Thanks.

Mike
```
 From: Mike Horvath Subject: Re: Stupid math help Date: 10 Nov 2016 19:37:28 Message: <5824cc78\$1@news.povray.org>
```On 11/10/2016 1:10 PM, Mike Horvath wrote:
> I have this formula from Wikipedia:
>
> [itex]A_v = [/itex] [itex]\log_2[/itex] [itex]A^2[/itex]
>
> How do I use this in POV-Ray? What is the correct syntax? Thanks.
>
>
> Mike

Never mind. I guessed the correct syntax.

Mike
```
 From: Tor Olav Kristensen Subject: Re: Stupid math help Date: 11 Nov 2016 03:35:01 Message:
```Mike Horvath <mik### [at] gmailcom> wrote:
> On 11/10/2016 1:10 PM, Mike Horvath wrote:
> > I have this formula from Wikipedia:
> >
> > [itex]A_v = [/itex] [itex]\log_2[/itex] [itex]A^2[/itex]
> >
> > How do I use this in POV-Ray? What is the correct syntax? Thanks.
> >
> >
> > Mike
>
>
> Never mind. I guessed the correct syntax.

It seems that \log_2 is the binary logarithm, which is not a standard float
function in POV-Ray (AFAIK).

You can get around this by doing something like this:

#declare BinLogFn = function(x) { ln(x)/ln(2) }

#declare Q = 8; // 2^3 = 8
#declare P = BinLogFn(Q);

#debug "\n\n"
#debug concat("2^", str(P, 0, -1), " = ", str(Q, 0, -1))
#debug "\n\n"

- But if you found the correct syntax, then you are probably aware of this.

--
Tor Olav
http://subcube.com
```