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Index › Programming Questions & Help › Syntax Questions › Translating single objects among multiple
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Translating single objects among multiple (Read 940 times)
sonic
Translating single objects among multiple
Nov 6th, 2009, 9:44am  
I'd like to use translate and rotate on just a few lines that are being drawn amongst hundreds. Is there a simple way to do this?? It seems that translate changes the coordinate system for everything being drawn.
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PhiLho 
Re: Translating single objects among multiple
Reply #1 - Nov 6th, 2009, 11:21am  
Look at pushMatrix() Smiley
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sonic
Re: Translating single objects among multiple
Reply #2 - Nov 8th, 2009, 7:52am  
I have looked at it, PhiLho, but it's not clear how I would use it in a method in which I use a for loop to draw 200 objects from an array of objects every frame, and I only want handful of them to translate . . .
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blindfish
Re: Translating single objects among multiple
Reply #3 - Nov 8th, 2009, 8:10am  
How do you determine which ones you want to translate?  Presumably a condition...  So wrap the pushMatrix/popMatrix calls around the translation code within this condition.
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Where is the what if the what is in why?
 
sonic
Re: Translating single objects among multiple
Reply #4 - Nov 9th, 2009, 2:02am  
OK - I've got it working now, thanks. I have a follow-up question, though: how can I rotate a two-dimensional object about its own axis (i.e. spin it). I've tried rotate(), but that rotates things about the axis of the entire grid, it seems.
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blindfish
Re: Translating single objects among multiple
Reply #5 - Nov 9th, 2009, 5:11am  
IIRC you first need to translate() to the desired axis of rotation.  The problem with that is you would need to be using translate to position the object on screen.  Alternatively you can use trigonometry and write methods to rotate the local coordinates of the objects...

That's a bit of a rushed and not thought-through answer; but this is something that has been asked before so I'm sure you might find something more detailed if you do a search Wink
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