b2MouseJoint Class
A mouse joint is used to make a point on a body track a specified world point. This a soft constraint with a maximum force. This allows the constraint to stretch and without applying huge forces. An instance of this class is created by B2World/createMouseJoint or createMouseJoint
Example:
// using native b2World
var b2x = x / this._world.scale;
var b2y = (System.height-y) / this._world.scale;
var mouseJointDef = {
maxForce : 2500,
frequencyHz : 10000,
dampingRatio : 0.0,
targetX : b2x,
targetY : b2y
};
// crate mouse joint
this._mouseJoint = this._world.createMouseJoint(this._ground, body, mouseJointDef, true);
// OR (using framework PhysicsScene)
// mouse joint definition
var mouseJointDef = {
maxForce : 10000,
frequencyHz : 1000,
dampingRatio : 0.0,
targetX : table.x2box2d(x), // specified in box2d coords
targetY : table.y2box2d(y) // specified in box2d coords
};
this.joint = table.createMouseJoint(table.ground, this.paddle, mouseJointDef, true);
Methods
getTarget
() Multivalue
Use this to get the target point. The target point is the point where the joint tries to move the connected body.
Returns:
Multivalue: Pair of float values: x and y coordinate of target point.
Example:
var (b2x, b2y) = this._mouseJoint.getTarget();
// convert box2d coordinates to screen coordinates
var y = -1*b2y * this._world.scale + System.height;
var x = b2x * this._world.scale;
setTarget
(
xy
Use this to update the target point. The target point is the point where the joint tries to move the connected body.
Example:
....onPointerDragged = function(sender, x, y)
{
if (this._mouseJoint) {
// convert screen coordinates to box2d coordinates
var b2y = (System.height-y) / this._world.scale;
var b2x = x / this._world.scale;
this._mouseJoint.setTarget(b2x, b2y);
}
}