[pstricks] Some Questions about pst-3dplot

[Alan Ristow]

VAFA KHALIGHI wrote:
> 1- Is there any guide where I can learn post script notation for 
> mathematical expressions well? i.e *x^3* is written as *x 3 exp* in 
> postscript notation.

The canonical reference for that is the Postscript Language Reference 
Manual (the "Red Book"):

http://www.adobe.com/products/postscript/pdfs/PLRM.pdf

If all you want is to quickly get some idea of the syntax and some of 
the commands available, though, you might prefer the Postscript Language 
Tutorial and Cookbook (the "Blue Book"):

http://partners.adobe.com/public/developer/en/ps/sdk/sample/BlueBook.zip
http://partners.adobe.com/public/developer/en/ps/sdk/sample/GreenBook.zip

> 2- When you want to skech a function of two variables, do you really 
> need to have
> ** 
> *\psset{Alpha=25,Beta=15}*
>  and what happenes if you do not put it? will you get the wrong graph?

Alpha and Beta have default values that will be used if you do not set 
them explicitly (I don't recall offhand what the defaults are, but 
you'll find them somewhere in the docs). By not setting them explicitly 
you won't get a "wrong graph," but you might get a graph that is 
difficult to read or does not clearly display the feature you wish to 
display.

> 3- How do you know which valuve of Alpha and Beta you need to use?

There's no "right" value for Alpha and Beta -- you just set them so the 
graph you produce looks the way you wish and communicates your message. 
I rarely use pst-3dplot, so when I do I set Alpha and Beta by trial and 
error. Once you've gained some experience with it you'll probably have a 
more intuitive feel for the appropriate values to use in any situation. 
You might also try studying the explanation given in the docs -- it 
might give you a better feel for what these parameters do and help you 
select appropriate values.

Alan