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Index › Programming Questions & Help › Syntax Questions › Atan2 question

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Atan2 question (Read 1185 times)

magnos

Atan2 question
Aug 19^th, 2005, 8:42pm

Hello,

I have a question to 'atan2' in processing.
Regarding the code below, I want to assure myself that the way I write it is correct...
I am a bit irritated that I have to invert the value of atan2...

...since this chart says I dont, but propably its because I am calculating the xy position to a negative value, no?

Code:


void setup()
{
  size(500,500);
}

void draw()
{
background(255);

float xmiddle = width/2;
float ymiddle = height/2;

float angle = -(atan2(mouseY - ymiddle, mouseX - xmiddle) - PI/2);

float d = dist(xmiddle, ymiddle, mouseX, mouseY);

float xp   = sin(angle)  * (d)    + width/2;
float yp   = cos(angle)   * (d)    + height/2;

beginShape(LINES);
vertex(width/2, height/2);
vertex(xp, yp);
endShape();
}

« Last Edit: Aug 19^th, 2005, 10:03pm by magnos »

tource09

Re: Atan2 question
Reply #1 - Aug 20^th, 2005, 12:15pm

I think :

float angle = atan2(xmiddle-mouseX,ymiddle-mouseY);
float xp = sin(angle-PI) * (d) + width/2;
float yp = cos(angle-PI) * (d) + height/2;

Code:



void setup() 
{ 
  size(500,500); 
} 
 
void draw() 
{ 
background(255); 
 
float xmiddle = width/2; 
float ymiddle = height/2; 
 
float angle = atan2(xmiddle-mouseX,ymiddle-mouseY); 
 
float d = dist(xmiddle, ymiddle, mouseX, mouseY); 
 
float xp   = sin(angle-PI)  * (d)    + width/2; 
float yp   = cos(angle-PI)   * (d)    + height/2; 
 
beginShape(LINES); 
vertex(width/2, height/2); 
vertex(xp, yp); 
endShape(); 
}

tource09

Re: Atan2 question
Reply #2 - Aug 20^th, 2005, 11:52pm

Opps!

Code:


Die Funktion atan2...
x = r*cos(atan2(y,x)) < COS
y = r*sin(atan2(y,x)) < SIN

Code:



void setup() 
{ 
  size(500,500); 
} 
 
void draw() 
{ 
background(255); 
 
float xmiddle = width/2; 
float ymiddle = height/2; 
 
float angle = atan2(mouseY - ymiddle, mouseX - xmiddle); 
 
float d = dist(xmiddle, ymiddle, mouseX, mouseY); 
 
float xp   = cos(angle)  * (d)    + width/2; // < COS
float yp   = sin(angle)   * (d)    + height/2; // < SIN 
 
beginShape(LINES); 
vertex(width/2, height/2); 
vertex(xp, yp); 
endShape(); 
}

magnos YaBB Newbies Offline Posts: 14	Re: Atan2 question Reply #3 - Aug 22^nd, 2005, 6:25pm OMG - Im all red for the shame. Thanks for pointing my nose in my mistake!

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