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Index › Programming Questions & Help › Syntax Questions › Fade-in effect due to low framerate !
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Fade-in effect due to low framerate ?! (Read 530 times)
mattjakob
Fade-in effect due to low framerate ?!
May 2nd, 2007, 4:02pm  
Hi.
Running this simple script:

Code:

void setup()
{
  size(800,800);
  frameRate(1);
}

void draw() {
  //probabilities for 3 different cases (these need to add up to 100% since something always occurs here!)
  float red_prob   = 0.10;		  // 10% chance of red color occurring
  float green_prob = 0.60 + red_prob;   // 60% chance of green color occuring
  float blue_prob  = 0.30 + green_prob; // 30% chance of blue color occuring
  float num = random(1);		    // pick a random number between 0 and 1
  if (num < red_prob) {
    fill(255,0,0,50);
  } 
  else if (num < green_prob) {
    fill(0,255,0,50);
  } 
  else {
    fill(0,0,255,50);
  }
  ellipse(random(width),random(height),16,16);
}


You'll notice that spots appear to "fade in" instead of being printed promptly. I noticed this while lowering the framerate. You know why?
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&&----------------------------------&& aittaM ~ Jakob&&
 
jaylfk
Re: Fade-in effect due to low framerate ?!
Reply #1 - May 2nd, 2007, 4:57pm  
Remove the alpha value in fill()

e.g fill(0,0,255);
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mattjakob
Re: Fade-in effect due to low framerate ?!
Reply #2 - May 2nd, 2007, 4:59pm  
What if I want to mantain it ?
lol

I did understood that this "fade in" effect was due the alpha value of the fillShape() but I cant understand why...
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&&----------------------------------&& aittaM ~ Jakob&&
 
davbol
Re: Fade-in effect due to low framerate ?!
Reply #3 - May 2nd, 2007, 5:01pm  
This may seem like an odd suggestion, but:  put a "background(255)" call right after your size() call.  Now when you run the sketch what color is the background?  White or gray?

Based on what you've described, my guess is you'll see gray, which indicates a problem - specifically, this one: http://processing.org/discourse/yabb_beta/YaBB.cgi?board=SoftwareBugs;action=display;num=1173650269

So, what's happing is that the internal buffer didn't get properly set up, and will have alpha values of 0, except where your ellipses set it to 50.  So each frame when it's blitted to the screen, it will add to itself and "accumulate" your ellipses in the way you've noticed.

Further prove it by putting "if (frameCount==1)" before your ellipse statement, so that ONLY one ellipse is ever drawn.  Do they still "accumulate"?

What to do?  With the background() statement still in place, alter your setup() call as:  setup(800,800,P3D);
Now run the sketch, does it work as expected?
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