In article <399feed3@news.povray.org>, "Thorsten Froehlich" 
<tho### [at] trfde> wrote:

> This still doesn't answer my question: Why?
> Why would more OO features in the scene language improve its usability?

I've often wished I could store a bunch of different types of data for a 
data structure in one chunk. Objects are an obvious place to put them. I 
had to settle for a bunch of global arrays, and eventually gave up.
The technique of #declaring a bunch of variables and #indluding a file 
is clumsy and can lead to variable name conflicts. Macros don't have 
variable numbers of parameters, so you sometimes have to resort to the 
same thing: #declaring variables before calling the macro. Long lists of 
macro parameters are difficult to keep track of. If object-oriented 
features were added, you could simply declare an object that does 
whatever was done by #including or calling a macro. For example, a lens 
flare object could be used like this:

#declare MyFlare = object {PlainLensFlare};

MyFlare.SetSize(5);
MyFlare.SetPos(< 5, 1, 6>);
MyFlare.SetColor(< 1, 0, 0.5>);
object {MyFlare.CalculateFlare();}

#declare MyFlare = object {SparkleLensFlare};
MyFlare.SetSize(2);
MyFlare.SetPos(<-5, 1, 6>);
MyFlare.SetColor(< 0, 1, 0>);
object {MyFlare.CalculateFlare();}

MyFlare.SetPos(< 0, 5, 6>);
MyFlare.SetColor(< 1, 1, 0>);
object {MyFlare.CalculateFlare();}

This would make 3 lens flares, a purple one to the right, a smaller 
green one to the left, and a yellow one above. You would only need to 
specify the parameters which you want to change, you could have as many 
as you want with no trouble, and you would have far fewer problems with 
variable name collision, since you would only need to watch out for the 
object names, not the parameters. If you wanted to make a slightly 
different lens flare, you wouldn't have to copy/paste a bunch of code 
from the original include and modify it, you could just make an object 
from one of the original objects and override some of the member macros.


> Would it be easier to learn? 

No, but since the existing language wouldn't need to be disturbed, you 
wouldn't have to learn it. It would be considerably easier to learn than 
C++, though.


> Would it be fast to parse? 

It probably wouldn't be noticeably slower without benchmarking, and 
could possibly allow doing some things in a way that would parse faster 
than previously possible.


> Would it allow porting C/C++/Java programs to POV-script?

No more than you can already port C or Pascal programs to POV-Script. 
Why would you want to do such a thing, anyway?


> In short : What are the _practical_ benefits for the scene 
> description, the primary purpose of the POV scene description 
> language?

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

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