Hi there,

I have written a class that scales and rotates a box in 3D. At the moment there is a variable called 'angle' that simply gets incremented in my 'update' method:

Code:

angle += 0.01;

  if(angle > TWO_PI) { 
    angle = 0.0; 
  }
 

Then in my 'render' method, I use that variable to rotate the box:

Code:

void render() {
    rectMode(CENTER);
    noStroke();
    fill(153,75);
    pushMatrix();
    // position object
    translate(x, y, -200);
    pushMatrix();
    // rotate object using 'angle' variable
    rotateX(angle);
    rotateY(angle);
    rotateZ(90);
    // draw box using location vectors
    box(loc.x,loc.y,loc.z);
    popMatrix();
    popMatrix();
  }
 

That all seems to work fine. However, what I am trying to do is get the box to rotate in response to the mouse x/y position, so that the direction of rotation shifts in the opposite direction of the mouse. Kind of like Yugo's 'Rosebox' piece (done in Director): http://yugop.com/ver3/index.asp?id=30

Does anyone know how to do this? I'm sure it involves using mouseX and mouseY in relation to the 'angle' variable - but I can't get it to work. Any help would be much appreciated as always :)

cheers,
Matt

For a direct mouseX/Y to rotation, you can use something like:

Code:

//gives a float between -1 and 1 depending on mouseX
float mx=((float)mouseX-(width/2.0))/(width/2.0);
//as above, but for mouseY
float mx=((float)mouseX-(height/2.0))/(height/2.0); 

To dampen it, you'll need to store a speed of change of angle (e.g. -0.1 radians/frame) and change the angle by that ammount, and then work out if the change in mx/my is larger than the change in angle will be, to set the new speed of change of angle.

I've applied your code to the following:

Code:

float ax = 0.0;
float ay = 0.0;
float rSize;  // rectangle size

void setup() 
{
  size(200, 200, P3D);
  rSize = width/4;  
  noStroke();
  fill(204, 204);
  framerate(30);
}

void draw() 
{
  background(0);

  //gives a float between -1 and 1 depending on mouseX 
  float mx=((float)mouseX-(width/2.0))/(width/2.0); 
  //as above, but for mouseY 
  float my=((float)mouseX-(height/2.0))/(height/2.0);

  ax += mx;
  ay += my;

  translate(width/2, height/2);

  rotateX(ax);
  rotateY(ay);
  rect(-rSize, -rSize, rSize*2, rSize*2);

}
 

Is that the correct way to apply it? I does kind of work - although the spinning gets a bit crazy when the mouse approaches the top left corner.