/**
* Compute the upper bound on time before two shapes penetrate. Time is represented as a fraction
* between [0,tMax]. This uses a swept separating axis and may miss some intermediate,
* non-tunneling collision. If you change the time interval, you should call this function again.
* Note: use Distance to compute the contact point and normal at the time of impact.
*
* @param output
* @param input
*/
public void timeOfImpact(TOIOutput output, TOIInput input)
{
// CCD via the local separating axis method. This seeks progression
// by computing the largest time at which separation is maintained.
++toiCalls;
output.state = TOIOutputState.UNKNOWN;
output.t = input.tMax;
DistanceProxy proxyA = input.proxyA;
DistanceProxy proxyB = input.proxyB;
sweepA.set(input.sweepA);
sweepB.set(input.sweepB);
// Large rotations can make the root finder fail, so we normalize the
// sweep angles.
sweepA.normalize();
sweepB.normalize();
double tMax = input.tMax;
double totalRadius = proxyA.m_radius + proxyB.m_radius;
// djm: whats with all these constants?
double target = MathUtils.max(Settings.linearSlop, totalRadius - 3.0d * Settings.linearSlop);
double tolerance = 0.25d * Settings.linearSlop;
double t1 = 0d;
int iter = 0;
cache.count = 0;
distanceInput.proxyA = input.proxyA;
distanceInput.proxyB = input.proxyB;
distanceInput.useRadii = false;
// The outer loop progressively attempts to compute new separating axes.
// This loop terminates when an axis is repeated (no progress is made).
for (;;)
{
sweepA.getTransform(xfA, t1);
sweepB.getTransform(xfB, t1);
// System.out.printf("sweepA: %f, %f, sweepB: %f, %f",
// sweepA.c.x, sweepA.c.y, sweepB.c.x, sweepB.c.y);
// Get the distance between shapes. We can also use the results
// to get a separating axis
distanceInput.transformA = xfA;
distanceInput.transformB = xfB;
pool.getDistance().distance(distanceOutput, cache, distanceInput);
// System.out.printf("Dist: %f at points %f, %f and %f, %f. %d iterations",
// distanceOutput.distance, distanceOutput.pointA.x, distanceOutput.pointA.y,
// distanceOutput.pointB.x, distanceOutput.pointB.y,
// distanceOutput.iterations);
// If the shapes are overlapped, we give up on continuous collision.
if (distanceOutput.distance <= 0d)
{
// System.out.println("failure, overlapped");
// Failure!
output.state = TOIOutputState.OVERLAPPED;
output.t = 0d;
break;
}
if (distanceOutput.distance < target + tolerance)
{
// System.out.println("touching, victory");
// Victory!
output.state = TOIOutputState.TOUCHING;
output.t = t1;
break;
}
// Initialize the separating axis.
fcn.initialize(cache, proxyA, sweepA, proxyB, sweepB, t1);
// Compute the TOI on the separating axis. We do this by successively
// resolving the deepest point. This loop is bounded by the number of
// vertices.
bool done = false;
double t2 = tMax;
int pushBackIter = 0;
for (;;)
{
// Find the deepest point at t2. Store the witness point indices.
double s2 = fcn.findMinSeparation(indexes, t2);
// System.out.printf("s2: %f", s2);
// Is the configuration separated?
if (s2 > target + tolerance)
{
// Victory!
// System.out.println("separated");
output.state = TOIOutputState.SEPARATED;
output.t = tMax;
done = true;
break;
}
// Has the separation reached tolerance?
if (s2 > target - tolerance)
{
// System.out.println("advancing");
// Advance the sweeps
t1 = t2;
break;
}
// Compute the initial separation of the witness points.
double s1 = fcn.evaluate(indexes[0], indexes[1], t1);
// Check for initial overlap. This might happen if the root finder
// runs out of iterations.
// System.out.printf("s1: %f, target: %f, tolerance: %f", s1, target,
// tolerance);
if (s1 < target - tolerance)
{
// System.out.println("failed?");
output.state = TOIOutputState.FAILED;
output.t = t1;
done = true;
break;
}
// Check for touching
if (s1 <= target + tolerance)
{
// System.out.println("touching?");
// Victory! t1 should hold the TOI (could be 0.0).
output.state = TOIOutputState.TOUCHING;
output.t = t1;
done = true;
break;
}
// Compute 1D root of: f(x) - target = 0
int rootIterCount = 0;
double a1 = t1, a2 = t2;
for (;;)
{
// Use a mix of the secant rule and bisection.
double t;
if ((rootIterCount & 1) == 1)
{
// Secant rule to improve convergence.
t = a1 + (target - s1) * (a2 - a1) / (s2 - s1);
}
else
{
// Bisection to guarantee progress.
t = 0.5d * (a1 + a2);
}
double s = fcn.evaluate(indexes[0], indexes[1], t);
if (MathUtils.abs(s - target) < tolerance)
{
// t2 holds a tentative value for t1
t2 = t;
break;
}
// Ensure we continue to bracket the root.
if (s > target)
{
a1 = t;
s1 = s;
}
else
{
a2 = t;
s2 = s;
}
++rootIterCount;
++toiRootIters;
// djm: whats with this? put in settings?
if (rootIterCount == 50)
{
break;
}
}
toiMaxRootIters = MathUtils.max(toiMaxRootIters, rootIterCount);
++pushBackIter;
if (pushBackIter == Settings.maxPolygonVertices)
{
break;
}
}
++iter;
++toiIters;
if (done)
{
// System.out.println("done");
break;
}
if (iter == MAX_ITERATIONS)
{
// System.out.println("failed, root finder stuck");
// Root finder got stuck. Semi-victory.
output.state = TOIOutputState.FAILED;
output.t = t1;
break;
}
}
// System.out.printf("sweeps: %f, %f, %f; %f, %f, %f", input.s)
toiMaxIters = MathUtils.max(toiMaxIters, iter);
}