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Index › Programming Questions & Help › Syntax Questions › floating point pixels
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floating point pixels (Read 916 times)
carthach
floating point pixels
Mar 21st, 2010, 11:34am  
Hi,

Just a quick question regarding integer pixel values versus floating point pixel values. If I supply say, (50,50) as parameters to the point function, presumably this addresses this single pixel. But if I use (50.5,50.5), what is this referring to. Is it addressing the RGB elements at a sub pixel level?

Thanks,
Cárthach
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Smitty
Re: floating point pixels
Reply #1 - Mar 21st, 2010, 12:26pm  
The point function doesn't address a pixel; it plots a point in model-space.  If you haven't done any transformations (e.g., translate(), rotate(), scale() etc) then point(50,50) will indeed plot on the (50, 50)-pixel.  But if you've previously called, say, scale(4,4), then point(50,50) will plot on the (200,200)-pixel, and point (50.5, 50.5) will plot on the (202,202)-pixel.
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carthach
Re: floating point pixels
Reply #2 - Mar 21st, 2010, 1:30pm  
Thank you, that makes sense, but if I haven't done any scaling i.e. I've opened a Processing file and just added the following lines

point(50,50);
point(50.5,50.5);

what's the second statement actually referring to?
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PhiLho 
Re: floating point pixels
Reply #3 - Mar 21st, 2010, 3:33pm  
I think they refer to the same point: if you don't scale anything, floating point coordinates are just truncated to integer coordinates.
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carthach
Re: floating point pixels
Reply #4 - Mar 21st, 2010, 5:08pm  
I thought so too Phil, but when I try it I see two points. It's not a problem, I'm just curious!
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yconst
Re: floating point pixels
Reply #5 - Mar 21st, 2010, 5:19pm  
It makes a difference depending on the renderer you use:
Code:
import processing.opengl.*;

size(300,300,P3D); //Try OPENGL, P2D, JAVA2D
//hint(ENABLE_OPENGL_4X_SMOOTH); //This apparently has no effect.
point(50.0,50.5);
point(50.1,51.5);
point(50.2,52.5);
point(50.3,53.5);
point(50.4,54.5);
point(50.5,55.5);
point(50.6,56.5);
point(50.7,57.5);
point(50.8,58.5);
point(50.9,59.5);
point(51.0,60.5);

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Yiannis Chatzikonstantinou
volatile prototypes
 
Smitty
Re: floating point pixels
Reply #6 - Mar 21st, 2010, 5:38pm  
carthach wrote on Mar 21st, 2010, 5:08pm:
I thought so too Phil, but when I try it I see two points. It's not a problem, I'm just curious!

What yconst said; in this case it may be rounding 50.5 up to 51.
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