hi, 

 

thanks for solution to previous query. I have added a simple zoom functionality to the sketch. However, when i zoom in, the ellipse jumps position and the mouse pointer controls segments at too large a distance. how can i fix this please?

 

float[][] ang;
int ind;

int zoom = 1;

boolean over = false;
boolean selected = false;
int posX, posY;
int offsetX, offsetY;
float radius = 20.0f;

void setup()
{
  size(512, 512);
  ang = new float[][]
  {
    {
      0, HALF_PI
    }
    ,
    {
      HALF_PI, PI
    }
    ,
    {
      PI+HALF_PI, TWO_PI
    }
    ,
    {
      PI, PI+HALF_PI
    }
  };

  posX = width/2;
  posY = height/2;
  smooth();
}

void draw()

{ 
  background(0, 0, 255);
  scale(zoom);

  ind = 0;
  float mx = mouseX-posX;
  float my = mouseY-posY;

  background(0, 0, 255);

  strokeWeight (0.3);
  stroke(255, 0, 0, 240);

 

  line(posX, 0, posX, height);
  line(0, posY, width, posY);
  fill (255, 0, 0, 190);
  ellipse (posX, posY, radius*2.0f, radius*2.0f);

  strokeWeight(2);

  if (my < 0) ind+=2;
  if (mx < 0) ind++;
  float rad = dist(0, 0, mx, my)*2;
 

  arc(posX, posY, rad, rad, ang[ind][0], ang[ind][1]);

  if (selected)
    strokeWeight (2.0f);

  fill (255, 0, 0, 190);

  if (key == '+') {
    zoom=2;
  }
  else if (key == '-') {
    zoom= 1;
  }
}

void mouseMoved() {
  over = false;
  if (sqrt(sq(mouseX-posX)+sq(mouseY-posY))<=radius) {
    over = true;
  }
}

void mousePressed() {
  if (over) {
    selected = true;
    offsetX = posX-mouseX;
    offsetY = posY-mouseY;
  }
}

void mouseReleased() {
  selected = false;
}

void mouseDragged()
{
  if (selected) {
    posX = max(0, min(mouseX+offsetX, width));
    posY = max(0, min(mouseY+offsetY, height));
  }
}

Two comments:

- with zoom <>1, your viewport coordinates (the visible part of the coordinate system of your model) and the screen coordinates are not the same. Your model is drawn in viewport coordinates, the mouse pointer still in screen coordinates. You have to transform one of them into the other to get the mouse picking right.

- you have to define the center of your zoom. Must it be in the center of the screen coordinates or in the center of the drawn circle? At present, it is at (0,0), upper left corner. Depending on your choice, you have to adapt the x,y offset. See translate().