/// Initialize the bodies, anchors, and reference angle using a world
/// anchor point.
// Point-to-point constraint
// C = p2 - p1
// Cdot = v2 - v1
// = v2 + cross(w2, r2) - v1 - cross(w1, r1)
// J = [-I -r1_skew I r2_skew ]
// Identity used:
// w k % (rx i + ry j) = w * (-ry i + rx j)
// Angle constraint
// C = angle2 - angle1 - referenceAngle
// Cdot = w2 - w1
// J = [0 0 -1 0 0 1]
// K = invI1 + invI2
public void Initialize(Body bA, Body bB, Vec2 anchor) {
bodyA = bA;
bodyB = bB;
localAnchorA = bodyA.GetLocalPoint(anchor);
localAnchorB = bodyB.GetLocalPoint(anchor);
referenceAngle = bodyB.GetAngle() - bodyA.GetAngle();
}
// Point-to-point constraint
// C = p2 - p1
// Cdot = v2 - v1
// = v2 + cross(w2, r2) - v1 - cross(w1, r1)
// J = [-I -r1_skew I r2_skew ]
// Identity used:
// w k % (rx i + ry j) = w * (-ry i + rx j)
// Angle constraint
// C = angle2 - angle1 - referenceAngle
// Cdot = w2 - w1
// J = [0 0 -1 0 0 1]
// K = invI1 + invI2
public void Initialize(Body b1, Body b2, Vector2 anchor)
{
bodyA = b1;
bodyB = b2;
localAnchorA = bodyA.GetLocalPoint(anchor);
localAnchorB = bodyB.GetLocalPoint(anchor);
referenceAngle = bodyB.GetAngle() - bodyA.GetAngle();
}
/// Initialize the bodies, anchors, and reference angle using a world
/// anchor point.
// Point-to-point constraint
// C = p2 - p1
// Cdot = v2 - v1
// = v2 + cross(w2, r2) - v1 - cross(w1, r1)
// J = [-I -r1_skew I r2_skew ]
// Identity used:
// w k % (rx i + ry j) = w * (-ry i + rx j)
// Angle constraint
// C = angle2 - angle1 - referenceAngle
// Cdot = w2 - w1
// J = [0 0 -1 0 0 1]
// K = invI1 + invI2
public void Initialize(Body bA, Body bB, Vec2 anchor)
{
bodyA = bA;
bodyB = bB;
localAnchorA = bodyA.GetLocalPoint(anchor);
localAnchorB = bodyB.GetLocalPoint(anchor);
referenceAngle = bodyB.GetAngle() - bodyA.GetAngle();
}
/// Initialize the bodies and offsets using the current transforms.
// Point-to-point constraint
// Cdot = v2 - v1
// = v2 + cross(w2, r2) - v1 - cross(w1, r1)
// J = [-I -r1_skew I r2_skew ]
// Identity used:
// w k % (rx i + ry j) = w * (-ry i + rx j)
// Angle constraint
// Cdot = w2 - w1
// J = [0 0 -1 0 0 1]
// K = invI1 + invI2
public void Initialize(Body bA, Body bB) {
bodyA = bA;
bodyB = bB;
Vec2 xB = bodyB.GetPosition();
linearOffset = bodyA.GetLocalPoint(xB);
float angleA = bodyA.GetAngle();
float angleB = bodyB.GetAngle();
angularOffset = angleB - angleA;
}
/// Initialize the bodies and offsets using the current transforms.
// Point-to-point constraint
// Cdot = v2 - v1
// = v2 + cross(w2, r2) - v1 - cross(w1, r1)
// J = [-I -r1_skew I r2_skew ]
// Identity used:
// w k % (rx i + ry j) = w * (-ry i + rx j)
// Angle constraint
// Cdot = w2 - w1
// J = [0 0 -1 0 0 1]
// K = invI1 + invI2
public void Initialize(Body bA, Body bB)
{
bodyA = bA;
bodyB = bB;
Vec2 xB = bodyB.GetPosition();
linearOffset = bodyA.GetLocalPoint(xB);
float angleA = bodyA.GetAngle();
float angleB = bodyB.GetAngle();
angularOffset = angleB - angleA;
}
static void Main(string[] args)
{
// Define the size of the world. Simulation will still work
// if bodies reach the end of the world, but it will be slower.
AABB worldAABB = new AABB
{
UpperBound = new Vector2(100, 100),
LowerBound = new Vector2(-100, -100)
};
// Define the gravity vector.
Vector2 gravity = new Vector2(0.0f, -10.0f);
// Do we want to let bodies sleep?
bool doSleep = true;
// Construct a world object, which will hold and simulate the rigid bodies.
World world = new World(worldAABB, gravity, doSleep);
// Define the ground body.
BodyDef groundBodyDef = new BodyDef();
groundBodyDef.Position = new Vector2(0.0f, -10.0f);
// Call the body factory which creates the ground box shape.
// The body is also added to the world.
Body groundBody = world.CreateBody(groundBodyDef);
// Define the ground box shape.
PolygonDef groundShapeDef = new PolygonDef();
// The extents are the half-widths of the box.
groundShapeDef.SetAsBox(50.0f, 10.0f);
// Add the ground shape to the ground body.
groundBody.CreateFixture(groundShapeDef);
// Define the dynamic body. We set its position and call the body factory.
BodyDef bodyDef = new BodyDef();
bodyDef.Position = new Vector2(0.0f, 4.0f);
Body body = world.CreateBody(bodyDef);
// Define another box shape for our dynamic body.
PolygonDef shapeDef = new PolygonDef();
shapeDef.SetAsBox(1.0f, 1.0f);
// Set the box density to be non-zero, so it will be dynamic.
shapeDef.Density = 1.0f;
// Override the default friction.
shapeDef.Friction = 0.3f;
// Add the shape to the body.
body.CreateFixture(shapeDef);
// Now tell the dynamic body to compute it's mass properties base
// on its shape.
body.SetMassFromShapes();
// Prepare for simulation. Typically we use a time step of 1/60 of a
// second (60Hz) and 10 iterations. This provides a high quality simulation
// in most game scenarios.
float timeStep = 1.0f / 60.0f;
int velocityIterations = 8;
int positionIterations = 1;
// This is our little game loop.
for (int i = 0; i < 100; ++i)
{
// Instruct the world to perform a single step of simulation. It is
// generally best to keep the time step and iterations fixed.
world.Step(timeStep, velocityIterations, positionIterations);
// Now print the position and angle of the body.
Vector2 position = body.GetPosition();
float angle = body.GetAngle();
Console.WriteLine("Step: {3} - X: {0}, Y: {1}, Angle: {2}", new object[] { position.X.ToString(), position.Y.ToString(), angle.ToString(), i.ToString() });
}
// When the world destructor is called, all bodies and joints are freed. This can
// create orphaned pointers, so be careful about your world management.
Console.ReadLine();
}
