On Wed, 29 Mar 2000 23:00:31 +1000, Nigel Stewart wrote:
>
>> : I'd like to see loops and branches raised out of the scene
>> : description language
>>
>>   It's just easier and handier to them to be there. Just think about
>> all those outstanding include files and macros.
>
>	Yes, from a POV-script point of view, macros and stuff
>	are nice to have.  But I think from a data-oriented
>	point of view, it's cleaner to leave them out and
>	leave it open to other language environments to do
>	algorithmic processing.
>
>	Therefore - XML is a data view.  POV-script remains
>	as an alternative - a custom, text oriented POV
>	specific, and POV optimised platform. 

First let me say that I like XML (and I do hand-code it, and I also
think that vi is the best HTML-editor), but I think that omitting the
algorithmic elements of POV-Script in POVML (or whatever we would like
to call it) would be a mistake.

Consider this fragment of POV-Script:

        #declare i = 0;  
        #while (i < 360)  

            object {
                vesta   
                translate <830, 50+10, 0>
                rotate <0, i, 0>
            }       

            #declare i = i + 12; 
        #end    

This puts 30 "vesta" objects in a circle of 830 pov-units radius. 

If this would be converted to

    <object name="vesta">
	<translate><vector>830 60 0</vector></translate>
	<rotate><vector>0, 0, 0</vector></rotate>
    </object>
    <object name="vesta">
	<translate><vector>830 60 0</vector></translate>
	<rotate><vector>0, 12, 0</vector></rotate>
    </object>
    .
    .
    .
    <object name="vesta">
	<translate><vector>830 60 0</vector></translate>
	<rotate><vector>0, 348, 0</vector></rotate>
    </object>

It isn't a circle of objects any more. These are 30 independent objects
which just happen to form a circle.

I do admit that I would prefer something like 

    <loop start="0" end="348" step="12">
	...
    </loop>

to 

    <set variable=i value="0" />
    <while expr="i < 360">
	...
	<set variable=i expr="i+12" />
    </while>

The latter doesn't really feel XMLish to me.

	hp

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