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Index › Programming Questions & Help › Syntax Questions › fade in, fade out
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fade in, fade out (Read 1076 times)
annemarie
fade in, fade out
Jul 21st, 2006, 9:54pm  
Hi all,

I would like to decrese the alpha layer in a shape, but it doesn't seem to work with this code:

   if (aniCounter >= 30) {
     int fadeOut = 255;
     fadeOut--;
     if(fadeOut <= 1) {fadeOut = 0; }
     r[9] = 15; g[9] = 245; b[9] = 255;
     alph[9]=fadeOut;
   }

I have some code that increases the alpha value, but I can't get this code to decrease it again ...

r[13] = 15; g[13] = 245; b[13] = 255;
     alph[13]=alph[13]+5; if (alph[13] < 0) { alph[13] = 255; }

thanks for your help!
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pi r 2
Re: fade in, fade out
Reply #1 - Jul 25th, 2006, 2:20am  
Here is some code I wrote for a simple demo of a square with pulsing transparancy. You can extract the logic I used (when the alpha val gets to its min or max, negate the rate of change:


int alphaVal, alphaDelta;

void setup() {
 alphaVal = 255; // initial value
 alphaDelta = 1; // rate of change
 size(400, 400);
 framerate(100); // slow f.r. down to pulse smoothly
 noStroke();
 rectMode(CENTER);
}

void draw() {
  background(120, 0, 120);
  fill(255, 255, 255, alphaVal);
  rect(width/2, height/2, width/2, width/2); 
 
 if ((alphaVal == 0) || (alphaVal == 255))
    alphaDelta = -alphaDelta;

  alphaVal+= alphaDelta;
}


hope that helps.
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[b]pi r squared
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st33d
Re: fade in, fade out
Reply #2 - Jul 25th, 2006, 11:56am  
Hrmm, so if aniCounter is greater than or equal to 30 then set the alpha value to 255.

Then decrement by one.

Then set some colour values and assign the alpha value.

Following your logic in that code block alpha will always be 254. You keep resetting it to 255 before you do anything with it. Could that be the problem?
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