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Index › Programming Questions & Help › Programs › Why jitter with moving curves
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Why jitter with moving curves? (Read 955 times)
sonic
Why jitter with moving curves?
Oct 20th, 2009, 12:05pm  
If you run the code below, at some point within the first couple minutes you should see floating curves whose edges occasionally 'snap' into and out of place - it's not completely smooth and has an obvious jittery quality. Can someone explain this to me, and is there a way to eliminate it?


import processing.opengl.*;

void setup() {
 size(720, 720, OPENGL);
 frameRate(40);
}

float a = random(-1, 1);
float b = random(-1, 1);
float c = random(-1, 1);
float d = random(-1, 1);
float e = random(-1, 1);
float f = random(-1, 1);
float g = random(-1, 1);
float h = random(-1, 1);


void draw() {
 background(75, 60, 85);

 a = a + .002;
 b = b + .0025;
 c = c + .001;
 d = d + .0015;
 e = e + .0005;
 f = f + .003;
 g = g + .0035;
 h = h + .0015;

 noStroke();
 fill(20, 220);
 curve(width/2+sin(b)*(width/2+100), width/2+sin(c)*(width/2+100), width/2+sin(d)*(width/2+100), width/2+sin(e)*(width/2+100), width/2+sin(f)*(width/2+100), width/2+sin(g)*(width/2+100), width/2+sin(h)*(width/2+100), width/2+sin(a)*(width/2+100));
}
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PhiLho 
Re: Why jitter with moving curves?
Reply #1 - Oct 21st, 2009, 12:00am  
It might be a problem with the renderer. I see the same issue with P3D but not with default one (JAVA2D).
I think it is when going over some critical numbers (PI or 2*PI for example).
I used
Code:
void mousePressed()
{
  println(a + " " + b + " " + c + " " + d + " " + e + " " + f + " " + g + " " + h);
}

to check that.
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sonic
Re: Why jitter with moving curves?
Reply #2 - Oct 21st, 2009, 2:10am  
Thanks, PhiLho - that's very helpful. I just assumed that the OpenGL graphics would be superior. I suppose I should report this as a bug? It's possibly a problem with the anti-aliasing algorithms?

I have a couple of related questions. First, since I'm now using the default renderer, does it make a difference whether I put smooth() in setup or within draw? Second, does it make sense to use both smooth() and bezierDetail if I'm working with bezier curves? And finally, if you  look at this image:

http://www.mti.dmu.ac.uk/~rherrema/graphics/sf-05757.tif

you will see how jagged are the lines on the curves. Since I'd like to print out some of these frame grabs, this is a real problem. What is the best way to solve this? Run at very large resolution?

Again, many thanks for your help.
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PhiLho 
Re: Why jitter with moving curves?
Reply #3 - Oct 21st, 2009, 2:56am  
It is better to put smooth() in setup, it is a global setting.
bezierDetail(): the reference says it is not useful in JAVA2D.
And for printing, yes, larger images can help. Or use PDF output (vector based).
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sonic
Re: Why jitter with moving curves?
Reply #4 - Oct 21st, 2009, 3:31am  
Do you mean convert the TIFF to PDF? saveFrame() doesn't offer PDF . . .
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PhiLho 
Re: Why jitter with moving curves?
Reply #5 - Oct 21st, 2009, 6:50am  
See PDF Export.
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