Processing 1.0 - Processing Discourse - Making arrays of pixels in a circle

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Making arrays of pixels in a circle (Read 874 times)

bugscripts

Making arrays of pixels in a circle
Jan 24^th, 2007, 6:50pm

I am making a game with pixel-sized particles. Is there a way to add to two existing arrays, particlesx and particlesy, a value in each for each point inside the circle?
Here is the code I used for adding one pixel where the mouse is clicked, which is what I want to do, only drop down a circle of particles instead of one:

if(mousePressed)
{
if(mode == "draw")
{

if(!particle_exists(mouseX, mouseY))
{
particlesx = append(particlesx, mouseX);
particlesy = append(particlesy, mouseY);
}
}
}

JohnG

Re: Making arrays of pixels in a circle
Reply #1 - Jan 24^th, 2007, 7:02pm

You could try putting something like this instead of the straightforwards single particle addition:

Code:

float radius=3;
int nummberToAdd=6;
for(int i=0;i<numberToAdd;i++)
{
  particlesx=append(particlesx,mouseX+radius*sin(i*(TWO_PI/numberToAdd)));
particlesy=append(particlesy,mouseY+radius*cos(i*(TWO_PI/numberToAdd)));
}

bugscripts YaBB Newbies Offline Posts: 8	Re: Making arrays of pixels in a circle Reply #2 - Jan 24^th, 2007, 10:05pm That seems to work with a few changes, but is there a way to make it fill the circle, like a paint program? Thanks!

JohnG

Re: Making arrays of pixels in a circle
Reply #3 - Jan 24^th, 2007, 10:42pm

It should be possible, though it could be quite a slow operation if you're adding a lot of things.

Code:

int radius=3; // or whatever
float sqRadius=sq(radius); // calculate once only.
for(int x=-radius;x<=radius;x++)
{
  for(int y=-radius;y<=radius;y++)
  {
    if(sq(x)+sq(y) <= sqRadius)
    {
	particlesx=append(particlesx,mouseX+x);
	particlesy=append(particlesy,mouseY+y);
    }
  }
}

bugscripts YaBB Newbies Offline Posts: 8	Re: Making arrays of pixels in a circle Reply #4 - Jan 25^th, 2007, 12:30am That seems to only make a quarter of a circle. (As you may have guessed, I'm not very good at math)

JohnG Ex Member	Re: Making arrays of pixels in a circle Reply #5 - Jan 25^th, 2007, 12:40am I just tested it, and it definitely does a full circle, since it checks every pixel from -radius to radius in the x and y axes to see if the distance from the middle is less than or equal to the radius of the circle.

bugscripts YaBB Newbies Offline Posts: 8	Re: Making arrays of pixels in a circle Reply #6 - Jan 25^th, 2007, 1:00am Hmm, I re-copied and pasted it and it made a circle. I must have copied something wrong...

Alterscape

Re: Making arrays of pixels in a circle
Reply #7 - Jan 25^th, 2007, 2:33am

If you're going to run this snippet of code to create the circle of particles often, you might want to rewrite it to use a lookup table rather than sin() and cos().

Write a snippet of code to populate an array with the values of sin() and cos() you're likely to use, then reference that array instead of using the sin() and cos() functions.

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