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Index › Programming Questions & Help › Programs › Glow

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Glow (Read 1438 times)

Glow
Aug 28^th, 2006, 7:13am

Hi,
Was just trying out a glow effect, and it works pretty well with shades of black and white.
But getting a gradient of RGB colours seems a little too complicated.
Like if I want the outer circles to have a tinge of blue, it would need a bunch of R,G and B values to colour the circles.
Anyone got a better idea for a glow that could blend in with the background colour, or at least give a torch-type glow?
Thanks!
SD :-)

Nothing is Impossible

Re: Glow
Reply #1 - Aug 28^th, 2006, 7:14am

//the code that I made
int r=100,c=0,ra=70,b=255,movt=1;
void setup()
{
size(200,200);
noStroke();
background(0);
framerate(30);
//noLoop();
}
void draw()
{
background(0);
glow(100,100,ra,b);
glow(150,100,ra,b);
if (ra>=100) movt=0;
if (ra<=0) movt=1;
if (movt==1) ra=ra+3; else ra=ra-3;
}
void glow(int r,int c,int ra,int b)
{
fill(b*.0392,100);ellipse(c,r,ra,ra);
fill(b*.0784,100);ellipse(c,r,ra*.8,ra*.8);
fill(b*.1176,100);ellipse(c,r,ra*.7,ra*.7);
fill(b*.196,100);ellipse(c,r,ra*.6,ra*.6);
fill(b*.3137,100);ellipse(c,r,ra*.5,ra*.5);
fill(b*.4705,100);ellipse(c,r,ra*.4,ra*.4);
fill(b*.5882,100);ellipse(c,r,ra*.34,ra*.34);
fill(b*.7058,100);ellipse(c,r,ra*.28,ra*.28);
fill(b*.8235,100);ellipse(c,r,ra*.2,ra*.2);
fill(b*.9019,100);ellipse(c,r,ra*.14,ra*.14);
fill(b,100);ellipse(c,r,ra*.12,ra*.12);
}

Nothing is Impossible

ddf

Re: Glow
Reply #2 - Sep 19^th, 2006, 5:10am

Rather than changing the color, you should just use the same color and change the alpha value. Also, once you draw the center ellipse you only have to draw the outer ellipses as lines. Something like this:

Code:


color c = color(255, 124, 0);
float rMin = 2;
float rMax = 4;
float r = rMin;
boolean grow = true;

void setup()
{
  size(200,200);
  framerate(30);
  ellipseMode(CENTER_RADIUS);
  smooth();
  r = rMin;
}
void draw()
{
 background(0);
 stroke(c);
 fill(c);
 ellipse(height/2, width/2, r, r);
 noFill();
 for (int i = 1; i < 20; i++)
 {
   stroke(red(c), green(c), blue(c), 255/i);
   strokeWeight(2);
   ellipse(height/2, width/2, r+i, r+i);
 }
 if ( grow ) 
 {
   r += 8/framerate;
   if ( r > rMax ) grow = false;
 }
 else
 {
   r -= 8/framerate;
   if ( r < rMin ) grow = true;
 } 
}

« Last Edit: Sep 28^th, 2006, 4:56pm by ddf »

http://www.compartmental.net

Re: Glow
Reply #3 - Sep 23^rd, 2006, 1:26pm

Thanks a zillion for that example.

What I also found out, is that if you want a good glow effect with transparency, you can create a tiny glow image in photoshop. Then use that image in the function given below.
This way, the alpha values of the pixels are adjusted according to its brightness. So the darkest pixels become most transparent and vice versa.
I got this idea from the StarNursery program.
Cheers!

void brightToAlpha(PImage b)
{
b.format = RGB;
for(int i=0; i < b.pixels.length; i++) {
float j=(brightness(b.pixels[i])/225)*100;
b.pixels[i] = color(255,255,255,j);
}
}

Nothing is Impossible

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