With the recent talk about the object collection I thought I might 
contribute an object I've been meaning to add.  It's simple, it lacks 
bolts, it's got a lot of messy looking calculations, and most of the 
dimensions are hard coded, but I think it gets at the gist of what it's 
supposed to be.

I posted it in p.t.scenes: 
http://news.povray.org/povray.text.scene-files/message/%3C47ec91d7%40news.povray.org%3E/#%3C47ec91d7%40news.povray.org%3E

Anyway, before I submit it, I was hoping to get some feedback, in 
general and specifically on this:  I like using a system where something 
like Main_Scene_File is a global variable and if it's already defined, a 
given include file knows not to use a self-contained demo scene.   It 
means an include file can stand alone as exactly one file.

Un-comment the line near the beginning which starts with 
"//#ifndef(Main_Scene_File)..." and render the file itself.

I know I've asked this before, and I've even wished for a 
main_scene_file keyword, but I don't remember how it turned out for the 
object collection.  What gobals can be truly global?

Thanks,
Charles

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"Charles C" <"nospam a nospam.com"> wrote in message 
news:47ec9326@news.povray.org...
> With the recent talk about the object collection I thought I might 
> contribute an object I've been meaning to add.  It's simple, it lacks 
> bolts, ...
> Anyway, before I submit it, I was hoping to get some feedback, in general 
> and specifically on this:  I like using a system where something like 
> Main_Scene_File is a global variable and if it's already defined, a given 
> include file knows not to use a self-contained demo scene.   It means an 
> include file can stand alone as exactly one file.
> ... I know I've asked this before, and I've even wished for a 
> main_scene_file keyword, but I don't remember how it turned out for the 
> object collection.  What gobals can be truly global?

It looks fine to me the way you've done it, with the line commented out and 
a description of how to use it at the top of the file. Those wishing to use 
this system can readily uncomment the line. I think it would cause problems 
if it were distributed without the line being commented out because it would 
break the scene file of anyone who didn't know the system.

I too would like some system defined way of interrogating the include file 
chain. My preference would probably be for a read-only array listing the 
chain of files. If the array dimension length is '1' you'd know that the 
file you're in is being rendered directly. Anyone needing additional info 
about the include file sequence could start trolling back through the 
contents of the array.

I don't recall ever seeing a concensus or any agreement from the POV-Team to 
include such a feature in a future version of POV-Ray. I seem to remember 
rather that the discussion exploded into one about rewriting the whole 
language. It might be worth re-opening discussions about this on 
povray.general on the off-chance of getting some simple solution into 3.7.

I've explored quite a few alternative ways of achieving similar results with 
the current version of POV-Ray and I've not found any solution that I would 
claim to be 'best' in all situations.

Regards,
Chris B.

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Chris B wrote:
> "Charles C" <"nospam a nospam.com"> wrote in message 
>> Anyway, before I submit it, I was hoping to get some feedback, in general 
>> and specifically on this:  I like using a system where something like 
>> Main_Scene_File is a global variable and if it's already defined, a given 
>> include file knows not to use a self-contained demo scene.   It means an 
>> include file can stand alone as exactly one file.
>> ... I know I've asked this before, and I've even wished for a 
>> main_scene_file keyword, but I don't remember how it turned out for the 
>> object collection.  What gobals can be truly global?
> 
> It looks fine to me the way you've done it, with the line commented out and 
> a description of how to use it at the top of the file. Those wishing to use 
> this system can readily uncomment the line. I think it would cause problems 
> if it were distributed without the line being commented out because it would 
> break the scene file of anyone who didn't know the system.
> 

OK, I'll submit it as is.  I try to check for things that might be 
defined already, Red or camera, but that definitely remains a drawback 
of doing this in SDL.  If main_scene_file were an actual keyword, it 
wouldn't break it.

> I too would like some system defined way of interrogating the include file 
> chain. My preference would probably be for a read-only array listing the 
> chain of files. If the array dimension length is '1' you'd know that the 
> file you're in is being rendered directly. Anyone needing additional info 
> about the include file sequence could start trolling back through the 
> contents of the array.

That sounds like an even more robust version of what I had in mind... :) 
   Would that be an array of strings?  Do you mean a special array which 
changes length dynamically?  If the starting-file performs some 
ifndef()'s and includes whatever it happens to need, then the array 
would grow.  But unless it shrinks by the time the parsing returns to 
the starting-file, you wouldn't be able to use that test.  OTOH, a 
strcmp() on the fist element should work.  Another possibility might be 
a float value/keyword like include_layer_number.

> 
> I don't recall ever seeing a concensus or any agreement from the POV-Team to 
> include such a feature in a future version of POV-Ray. I seem to remember 
> rather that the discussion exploded into one about rewriting the whole 
> language. It might be worth re-opening discussions about this on 
> povray.general on the off-chance of getting some simple solution into 3.7.

As far as a keyword and POV-Ray itself goes, Chris Cason responded to my 
   suggestion saying it may have some merit but took it in a slightly 
different direction: He implemented the alternate-file-render feature 
starting in beta 20b.  That addressed the convenience-of-editing include 
files, but not the self-demoing of include-file-objects that I was 
dreaming about.    (I guess I have a thing for standalone files whenever 
possible :-)

IIRC, I think he did mention that if there were such a variable, it 
might work better letting POV-Ray keep track of whether it's parsing the 
first file and have the keyword be a binary variable which toggles 
accordingly.  Maybe I'm mis-remembering.  It's been a while.

> 
> I've explored quite a few alternative ways of achieving similar results with 
> the current version of POV-Ray and I've not found any solution that I would 
> claim to be 'best' in all situations.
> 
> Regards,
> Chris B. 
> 
> 
I'd be interested to know what other ideas you've had.  Anything that 
does not break people's scenes if they don't use that system and makes t 
possible to do what I'm trying to do would satisfy me.  I suspect it's 
not possible without adding a keyword of some sort.


Charles

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