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flicker problem (Read 1130 times)
rct77
flicker problem
Jul 16th, 2007, 6:43pm  
I am attempting to create a black/white random noise pattern ("static"). The size of the animation must be 800x600. Generating this number of random pixles without bogging down the framerate has been a challenge, but Processing is able to handle it nicely. The problem is a troublesome flicker that I have been unable to get rid of.

Any suggestions on how to improve the code would be appreciatd!

Code:


int sx, sy, x, y, bright;

void setup()
{
   size(800,600);
   sx = width;
   sy = height;
}

void draw()
{
   loadPixels();
   for(x=0; x<sx; x=x+1) {
   for(y=0; y<sy; y=y+1) {
	int rn = (int) (Math.random() * 3);
	bright = (rn%2 == 0) ? 255 : 0;
	pixels[x+y*width] = color(bright);
   }
   }
   updatePixels();
}
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V
Re: flicker problem
Reply #1 - Jul 16th, 2007, 6:59pm  
draw your noise on a image and then draw all of it to the screen.. its called double buffering or as i sometimes call it. offscreen rendering.. if you keep drawing directly to screen output, you will noticed flicker coz of the refresh rate and vsync
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Victor Martins | www.pixelnerve.com/v
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JohnG
Re: flicker problem
Reply #2 - Jul 16th, 2007, 8:13pm  
As an aside, I think I can pretty much double the speed of your noise generation:

Change:
Code:
  int rn = (int) (Math.random() * 3);
 bright = (rn%2 == 0) ? 255 : 0;
 pixels[x+y*width] = color(bright);

to
Code:
pixels[x+y*width] = 0xFFFFFFFF ^ ((((int)random(3))%2) * 0x00FFFFFF);


(BTW, you do realise you've got a 2:1 ratio of white:black pixels? If you want to even it out, it's just (int)random(2) and no need for the %2.)
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rct77
Re: flicker problem
Reply #3 - Jul 17th, 2007, 2:02am  
Thanks for the input guys. The suggested changes have greatly improved the sketch, but unfortunately the flicker remains. I am new to Processing, but after poking around here a bit I put together the below code that I *think* implements double-buffering. Please let me know if this is correct, and if you have any additional thoughts on this.

Thanks!

Code:

PGraphics g; 
int sx, sy, x, y;

void setup()
{
  size(800, 600, P3D);
  sx = width;
  sy = height;
  g = createGraphics(800,600, P3D); 
}

void draw()
{
   g.beginDraw();
    g.loadPixels();

    for (x = 0; x < sx; x=x+1) { 
	for (y = 0; y < sy; y=y+1) { 
	  g.pixels[x+y*width] = 0xFFFFFFFF ^ ((int)random(2) * 0x00FFFFFF);
	}
    }
  g.updatePixels();
  g.endDraw();   
image(g,0,0); 
}
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V
Re: flicker problem
Reply #4 - Jul 17th, 2007, 10:53am  
what you're talking about is bad framerate.. you application is running really slow. why dont you just render a couple of noise images and then use those to simulate the effect? that would work just as nice and alot cheaper
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Victor Martins | www.pixelnerve.com/v
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