static void EstimateCrushing(cpBody body, cpArbiter arb, ref CrushingContext context)
{
cpVect j = arb.TotalImpulse();
context.magnitudeSum += (float)cpVect.cpvlength(j);
context.vectorSum = cpVect.cpvadd(context.vectorSum, j);
}
public override void Update(float dt)
{
base.Update(dt);
space.Step(dt);
SetSubTitle("Place objects on the scale to weigh them. The ball marks the shapes it's sitting on.\n");
// Sum the total impulse applied to the scale from all collision pairs in the contact graph.
// If your compiler supports blocks, your life is a little easier.
// You can use the "Block" versions of the functions without needing the callbacks above.
cpVect impulseSum = cpVect.Zero;
scaleStaticBody.EachArbiter(
(a, o) => ScaleIterator(scaleStaticBody, a, ref impulseSum)
, null);
// Force is the impulse divided by the timestep.
float force = cpVect.cpvlength(impulseSum) / dt;
// Weight can be found similarly from the gravity vector.
cpVect g = space.GetGravity(); // cpSpaceGetGravity();
float weight = cpVect.cpvdot(g, impulseSum) / (cpVect.cpvlengthsq(g) * dt);
SetSubTitle(string.Format("Total force: {0}, Total weight: {1}. ", force, weight));
// Highlight and count the number of shapes the ball is touching.
int count = 0;
ballBody.EachArbiter((a, o) => BallIterator(ballBody, a, ref count), null);
SetSubTitle(string.Format("The ball is touching {0} shapes.", count));
CrushingContext crush = new CrushingContext(0.0f, cpVect.Zero);
ballBody.EachArbiter((a, o) => EstimateCrushing(ballBody, a, ref crush), null);
float crushForce = (crush.magnitudeSum - cpVect.cpvlength(crush.vectorSum)) * dt;
if (crushForce > 10.0f)
{
SetSubTitle(string.Format("The ball is being crushed. (f: {0})", crushForce));
}
else
{
SetSubTitle(string.Format("The ball is not being crushed. (f: {0})", crushForce));
}
draw.Clear();
}
