[PD] Gem coordinates / OpenGL

B. Bogart ben at ekran.org
Thu Mar 9 17:11:41 CET 2006


Gem coords really only represent distances relative to the window aspect
ratio.

0,0,0 is in the middle, -4,-4,0 is the bottom left corner 4,4,0 is the
upper right corner. The camera is at 0,0,4...

That is for a square window.

The height of a gemwindow is always 8 units, -4 to 4, but depending on
the aspect ratio of the window the number of units wide changes. for a
2:1 window the left edge is -8 and the right 8. For a 4:3 window the
left is -5.333 and the right 5.333

try the tutorial at www.ekran.org/pd

..b.

David Powers wrote:
> So, follow up question:
>
> I can make lines with [polygon 2] - easy enough. But, there is one thing
> I still don't get - what are GEM coordinates supposed to represent? The
> length of "1" or "4" in GEM seems arbitrary. I'm sure there's a logical
> explanation though. I was thinking of trying to sketch out some weird
> things, and render them with GEM, but understanding the coordinate
> system would help a lot!
>
> Also, still interested in the OpenGL tutorial - are there any good
> reasons to use OpenGL wrappers over built in GEM functions? What might I
> be able to do better than GEM, or what is missing in GEM that these
> wrappers have?
>
> Thanks,
> David
>
> David Powers wrote:
>
>> Never mind, I guess I was trying to create it without an argument,
>> because I was going to check the arguments AFTER I created it. But
>> without the argument PD won't create it (though I think there should
>> be some default argument built in).
>> ~David
>>
>> David Powers wrote:
>>
>>> Hello,
>>>
>>> According to the GEM manual, there are "curve" and "polygon" objects
>>> in GEM. However, I'm not able to create them. Do they exist?
>>>
>>> Related question, how do I just draw some lines in GEM, is that
>>> possible? Do I need the openGL wrappers, and if so, does anyone know
>>> an easy openGL tutorial that might get me started? Or does someone
>>> have a really simple example patch they could send?
>>>
>>> Thanks,
>>> David
>>>
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>>
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>
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