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Index › Programming Questions & Help › Programs › Curve-Ellipse Intersection
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Curve-Ellipse Intersection (Read 925 times)
_hal9000_
Curve-Ellipse Intersection
Nov 11th, 2009, 1:10pm  
Hi, I´m doing a small game and need to check a collision between a curve, drawing with the mouse like the processing example, and a moving ellipse.

Basically, I store the mouse coordinates in a arraylist and then draw lines between the points stored. I know the equations to check line-circle intersection mathworld.wolfram.com/Circle-LineIntersection.html but the computation is very intense, with many square roots,  and I need to test the intersection with a lot of lines every frame.

I was thinking of checking the colors of the pixeis (the ellipse and th have different collors in my game) but I don´t know if we can access the video buffer in processing. Does anyone know any simpler method?
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TfGuy44
Re: Curve-Ellipse Intersection
Reply #1 - Nov 11th, 2009, 6:33pm  
It is possible to directly access the color of the pixel under the mouse.
For example:

void draw(){
 background(0);
 noStroke();
 fill(color(255,0,0));
 rect(10,10,20,20);
 fill(color(0,0,255));
 rect(10,70,20,20);
 fill(color(0,255,0));
 rect(70,10,20,20);
 fill(color(random(255),random(255),random(255)));
 rect(70,70,20,20);
 loadPixels();
 fill(pixels[(width*mouseY)+mouseX]);
 rect(40,40,20,20);
}

Hope this helps!
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_hal9000_
Re: Curve-Ellipse Intersection
Reply #2 - Nov 12th, 2009, 9:33am  
Thanks for your answer TF. I forgot this function loadPixels. If I can get the pixels around the mouse I can also get the pixels around the center of the ellipse.
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Cedric
Re: Curve-Ellipse Intersection
Reply #3 - Nov 12th, 2009, 11:07am  
or just  fill(get(mouseX,mouseY));
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