public void readCache(
SimplexCache cache,
DistanceProxy proxyA,
Transform transformA,
DistanceProxy proxyB,
Transform transformB) {
assert (cache.count <= 3);
// Copy data from cache.
m_count = cache.count;
for (int i = 0; i < m_count; ++i) {
SimplexVertex v = vertices[i];
v.indexA = cache.indexA[i];
v.indexB = cache.indexB[i];
Vec2 wALocal = proxyA.getVertex(v.indexA);
Vec2 wBLocal = proxyB.getVertex(v.indexB);
Transform.mulToOutUnsafe(transformA, wALocal, v.wA);
Transform.mulToOutUnsafe(transformB, wBLocal, v.wB);
v.w.set(v.wB).subLocal(v.wA);
v.a = 0.0f;
}
// Compute the new simplex metric, if it is substantially different than
// old metric then flush the simplex.
if (m_count > 1) {
float metric1 = cache.metric;
float metric2 = getMetric();
if (metric2 < 0.5f * metric1 || 2.0f * metric1 < metric2 || metric2 < Settings.EPSILON) {
// Reset the simplex.
m_count = 0;
}
}
// If the cache is empty or invalid ...
if (m_count == 0) {
SimplexVertex v = vertices[0];
v.indexA = 0;
v.indexB = 0;
Vec2 wALocal = proxyA.getVertex(0);
Vec2 wBLocal = proxyB.getVertex(0);
Transform.mulToOutUnsafe(transformA, wALocal, v.wA);
Transform.mulToOutUnsafe(transformB, wBLocal, v.wB);
v.w.set(v.wB).subLocal(v.wA);
m_count = 1;
}
}
/**
* Compute the closest points between two shapes. Supports any combination of: CircleShape and
* PolygonShape. The simplex cache is input/output. On the first call set SimplexCache.count to
* zero.
*
* @param output
* @param cache
* @param input
*/
public final void distance(
final DistanceOutput output, final SimplexCache cache, final DistanceInput input) {
GJK_CALLS++;
final DistanceProxy proxyA = input.proxyA;
final DistanceProxy proxyB = input.proxyB;
Transform transformA = input.transformA;
Transform transformB = input.transformB;
// Initialize the simplex.
simplex.readCache(cache, proxyA, transformA, proxyB, transformB);
// Get simplex vertices as an array.
SimplexVertex[] vertices = simplex.vertices;
// These store the vertices of the last simplex so that we
// can check for duplicates and prevent cycling.
// (pooled above)
int saveCount = 0;
simplex.getClosestPoint(closestPoint);
float distanceSqr1 = closestPoint.lengthSquared();
float distanceSqr2 = distanceSqr1;
// Main iteration loop
int iter = 0;
while (iter < MAX_ITERS) {
// Copy simplex so we can identify duplicates.
saveCount = simplex.m_count;
for (int i = 0; i < saveCount; i++) {
saveA[i] = vertices[i].indexA;
saveB[i] = vertices[i].indexB;
}
switch (simplex.m_count) {
case 1:
break;
case 2:
simplex.solve2();
break;
case 3:
simplex.solve3();
break;
default:
assert (false);
}
// If we have 3 points, then the origin is in the corresponding triangle.
if (simplex.m_count == 3) {
break;
}
// Compute closest point.
simplex.getClosestPoint(closestPoint);
distanceSqr2 = closestPoint.lengthSquared();
// ensure progress
if (distanceSqr2 >= distanceSqr1) {
// break;
}
distanceSqr1 = distanceSqr2;
// get search direction;
simplex.getSearchDirection(d);
// Ensure the search direction is numerically fit.
if (d.lengthSquared() < Settings.EPSILON * Settings.EPSILON) {
// The origin is probably contained by a line segment
// or triangle. Thus the shapes are overlapped.
// We can't return zero here even though there may be overlap.
// In case the simplex is a point, segment, or triangle it is difficult
// to determine if the origin is contained in the CSO or very close to it.
break;
}
/*
* SimplexVertex* vertex = vertices + simplex.m_count; vertex.indexA =
* proxyA.GetSupport(MulT(transformA.R, -d)); vertex.wA = Mul(transformA,
* proxyA.GetVertex(vertex.indexA)); Vec2 wBLocal; vertex.indexB =
* proxyB.GetSupport(MulT(transformB.R, d)); vertex.wB = Mul(transformB,
* proxyB.GetVertex(vertex.indexB)); vertex.w = vertex.wB - vertex.wA;
*/
// Compute a tentative new simplex vertex using support points.
SimplexVertex vertex = vertices[simplex.m_count];
Rot.mulTransUnsafe(transformA.q, d.negateLocal(), temp);
vertex.indexA = proxyA.getSupport(temp);
Transform.mulToOutUnsafe(transformA, proxyA.getVertex(vertex.indexA), vertex.wA);
// Vec2 wBLocal;
Rot.mulTransUnsafe(transformB.q, d.negateLocal(), temp);
vertex.indexB = proxyB.getSupport(temp);
Transform.mulToOutUnsafe(transformB, proxyB.getVertex(vertex.indexB), vertex.wB);
vertex.w.set(vertex.wB).subLocal(vertex.wA);
// Iteration count is equated to the number of support point calls.
++iter;
++GJK_ITERS;
// Check for duplicate support points. This is the main termination criteria.
boolean duplicate = false;
for (int i = 0; i < saveCount; ++i) {
if (vertex.indexA == saveA[i] && vertex.indexB == saveB[i]) {
duplicate = true;
break;
}
}
// If we found a duplicate support point we must exit to avoid cycling.
if (duplicate) {
break;
}
// New vertex is ok and needed.
++simplex.m_count;
}
GJK_MAX_ITERS = MathUtils.max(GJK_MAX_ITERS, iter);
// Prepare output.
simplex.getWitnessPoints(output.pointA, output.pointB);
output.distance = MathUtils.distance(output.pointA, output.pointB);
output.iterations = iter;
// Cache the simplex.
simplex.writeCache(cache);
// Apply radii if requested.
if (input.useRadii) {
float rA = proxyA.m_radius;
float rB = proxyB.m_radius;
if (output.distance > rA + rB && output.distance > Settings.EPSILON) {
// Shapes are still no overlapped.
// Move the witness points to the outer surface.
output.distance -= rA + rB;
normal.set(output.pointB).subLocal(output.pointA);
normal.normalize();
temp.set(normal).mulLocal(rA);
output.pointA.addLocal(temp);
temp.set(normal).mulLocal(rB);
output.pointB.subLocal(temp);
} else {
// Shapes are overlapped when radii are considered.
// Move the witness points to the middle.
// Vec2 p = 0.5f * (output.pointA + output.pointB);
output.pointA.addLocal(output.pointB).mulLocal(.5f);
output.pointB.set(output.pointA);
output.distance = 0.0f;
}
}
}
