/// <summary>
/// Get the contact manifold. Do not modify the manifold unless you understand the
/// internals of Box2D.
/// </summary>
/// <param name="manifold">The manifold.</param>
public void GetManifold(out Manifold manifold)
{
manifold = Manifold;
}
/// <summary>
/// Evaluate this contact with your own manifold and transforms.
/// </summary>
/// <param name="manifold">The manifold.</param>
/// <param name="transformA">The first transform.</param>
/// <param name="transformB">The second transform.</param>
private void Evaluate(ref Manifold manifold, ref Transform transformA, ref Transform transformB)
{
switch (_type)
{
case ContactType.Polygon:
Collision.Collision.CollidePolygons(ref manifold,
(PolygonShape)FixtureA.Shape, ref transformA,
(PolygonShape)FixtureB.Shape, ref transformB);
break;
case ContactType.PolygonAndCircle:
Collision.Collision.CollidePolygonAndCircle(ref manifold,
(PolygonShape)FixtureA.Shape, ref transformA,
(CircleShape)FixtureB.Shape, ref transformB);
break;
case ContactType.EdgeAndCircle:
Collision.Collision.CollideEdgeAndCircle(ref manifold,
(EdgeShape)FixtureA.Shape, ref transformA,
(CircleShape)FixtureB.Shape, ref transformB);
break;
case ContactType.EdgeAndPolygon:
Collision.Collision.CollideEdgeAndPolygon(ref manifold,
(EdgeShape)FixtureA.Shape, ref transformA,
(PolygonShape)FixtureB.Shape, ref transformB);
break;
case ContactType.LoopAndCircle:
LoopShape loop = (LoopShape)FixtureA.Shape;
loop.GetChildEdge(ref _edge, ChildIndexA);
Collision.Collision.CollideEdgeAndCircle(ref manifold, _edge, ref transformA,
(CircleShape)FixtureB.Shape, ref transformB);
break;
case ContactType.LoopAndPolygon:
LoopShape loop2 = (LoopShape)FixtureA.Shape;
loop2.GetChildEdge(ref _edge, ChildIndexA);
Collision.Collision.CollideEdgeAndPolygon(ref manifold, _edge, ref transformA,
(PolygonShape)FixtureB.Shape, ref transformB);
break;
case ContactType.Circle:
Collision.Collision.CollideCircles(ref manifold,
(CircleShape)FixtureA.Shape, ref transformA,
(CircleShape)FixtureB.Shape, ref transformB);
break;
}
}
/// <summary>
/// Compute contact points for edge versus circle.
/// This accounts for edge connectivity.
/// </summary>
/// <param name="manifold">The manifold.</param>
/// <param name="edgeA">The edge A.</param>
/// <param name="transformA">The transform A.</param>
/// <param name="circleB">The circle B.</param>
/// <param name="transformB">The transform B.</param>
public static void CollideEdgeAndCircle(ref Manifold manifold,
EdgeShape edgeA, ref Transform transformA,
CircleShape circleB, ref Transform transformB)
{
manifold.PointCount = 0;
// Compute circle in frame of edge
Vector2 Q = MathUtils.MultiplyT(ref transformA, MathUtils.Multiply(ref transformB, ref circleB._position));
Vector2 A = edgeA.Vertex1, B = edgeA.Vertex2;
Vector2 e = B - A;
// Barycentric coordinates
float u = Vector2.Dot(e, B - Q);
float v = Vector2.Dot(e, Q - A);
float radius = edgeA.Radius + circleB.Radius;
ContactFeature cf;
cf.IndexB = 0;
cf.TypeB = (byte)ContactFeatureType.Vertex;
Vector2 P, d;
// Region A
if (v <= 0.0f)
{
P = A;
d = Q - P;
float dd;
Vector2.Dot(ref d, ref d, out dd);
if (dd > radius * radius)
{
return;
}
// Is there an edge connected to A?
if (edgeA.HasVertex0)
{
Vector2 A1 = edgeA.Vertex0;
Vector2 B1 = A;
Vector2 e1 = B1 - A1;
float u1 = Vector2.Dot(e1, B1 - Q);
// Is the circle in Region AB of the previous edge?
if (u1 > 0.0f)
{
return;
}
}
cf.IndexA = 0;
cf.TypeA = (byte)ContactFeatureType.Vertex;
manifold.PointCount = 1;
manifold.Type = ManifoldType.Circles;
manifold.LocalNormal = Vector2.Zero;
manifold.LocalPoint = P;
ManifoldPoint mp = new ManifoldPoint();
mp.Id.Key = 0;
mp.Id.Features = cf;
mp.LocalPoint = circleB.Position;
manifold.Points[0] = mp;
return;
}
// Region B
if (u <= 0.0f)
{
P = B;
d = Q - P;
float dd;
Vector2.Dot(ref d, ref d, out dd);
if (dd > radius * radius)
{
return;
}
// Is there an edge connected to B?
if (edgeA.HasVertex3)
{
Vector2 B2 = edgeA.Vertex3;
Vector2 A2 = B;
Vector2 e2 = B2 - A2;
float v2 = Vector2.Dot(e2, Q - A2);
// Is the circle in Region AB of the next edge?
if (v2 > 0.0f)
{
return;
}
}
cf.IndexA = 1;
cf.TypeA = (byte)ContactFeatureType.Vertex;
manifold.PointCount = 1;
manifold.Type = ManifoldType.Circles;
manifold.LocalNormal = Vector2.Zero;
manifold.LocalPoint = P;
ManifoldPoint mp = new ManifoldPoint();
mp.Id.Key = 0;
mp.Id.Features = cf;
mp.LocalPoint = circleB.Position;
manifold.Points[0] = mp;
return;
}
// Region AB
float den;
Vector2.Dot(ref e, ref e, out den);
Debug.Assert(den > 0.0f);
P = (1.0f / den) * (u * A + v * B);
d = Q - P;
float dd2;
Vector2.Dot(ref d, ref d, out dd2);
if (dd2 > radius * radius)
{
return;
}
Vector2 n = new Vector2(-e.Y, e.X);
if (Vector2.Dot(n, Q - A) < 0.0f)
{
n = new Vector2(-n.X, -n.Y);
}
n.Normalize();
cf.IndexA = 0;
cf.TypeA = (byte)ContactFeatureType.Face;
manifold.PointCount = 1;
manifold.Type = ManifoldType.FaceA;
manifold.LocalNormal = n;
manifold.LocalPoint = A;
ManifoldPoint mp2 = new ManifoldPoint();
mp2.Id.Key = 0;
mp2.Id.Features = cf;
mp2.LocalPoint = circleB.Position;
manifold.Points[0] = mp2;
}
/// <summary>
/// Collides and edge and a polygon, taking into account edge adjacency.
/// </summary>
/// <param name="manifold">The manifold.</param>
/// <param name="edgeA">The edge A.</param>
/// <param name="xfA">The xf A.</param>
/// <param name="polygonB">The polygon B.</param>
/// <param name="xfB">The xf B.</param>
public static void CollideEdgeAndPolygon(ref Manifold manifold,
EdgeShape edgeA, ref Transform xfA,
PolygonShape polygonB, ref Transform xfB)
{
MathUtils.MultiplyT(ref xfA, ref xfB, out _xf);
// Edge geometry
_edgeA.V0 = edgeA.Vertex0;
_edgeA.V1 = edgeA.Vertex1;
_edgeA.V2 = edgeA.Vertex2;
_edgeA.V3 = edgeA.Vertex3;
Vector2 e = _edgeA.V2 - _edgeA.V1;
// Normal points outwards in CCW order.
_edgeA.Normal = new Vector2(e.Y, -e.X);
_edgeA.Normal.Normalize();
_edgeA.HasVertex0 = edgeA.HasVertex0;
_edgeA.HasVertex3 = edgeA.HasVertex3;
// Proxy for edge
_proxyA.Vertices[0] = _edgeA.V1;
_proxyA.Vertices[1] = _edgeA.V2;
_proxyA.Normals[0] = _edgeA.Normal;
_proxyA.Normals[1] = -_edgeA.Normal;
_proxyA.Centroid = 0.5f * (_edgeA.V1 + _edgeA.V2);
_proxyA.Count = 2;
// Proxy for polygon
_proxyB.Count = polygonB.Vertices.Count;
_proxyB.Centroid = MathUtils.Multiply(ref _xf, ref polygonB.MassData.Centroid);
for (int i = 0; i < polygonB.Vertices.Count; ++i)
{
_proxyB.Vertices[i] = MathUtils.Multiply(ref _xf, polygonB.Vertices[i]);
_proxyB.Normals[i] = MathUtils.Multiply(ref _xf.R, polygonB.Normals[i]);
}
_radius = 2.0f * Settings.PolygonRadius;
_limit11 = Vector2.Zero;
_limit12 = Vector2.Zero;
_limit21 = Vector2.Zero;
_limit22 = Vector2.Zero;
//Collide(ref manifold); inline start
manifold.PointCount = 0;
//ComputeAdjacency(); inline start
Vector2 v0 = _edgeA.V0;
Vector2 v1 = _edgeA.V1;
Vector2 v2 = _edgeA.V2;
Vector2 v3 = _edgeA.V3;
// Determine allowable the normal regions based on adjacency.
// Note: it may be possible that no normal is admissable.
Vector2 centerB = _proxyB.Centroid;
if (_edgeA.HasVertex0)
{
Vector2 e0 = v1 - v0;
Vector2 e1 = v2 - v1;
Vector2 n0 = new Vector2(e0.Y, -e0.X);
Vector2 n1 = new Vector2(e1.Y, -e1.X);
n0.Normalize();
n1.Normalize();
bool convex = MathUtils.Cross(n0, n1) >= 0.0f;
bool front0 = Vector2.Dot(n0, centerB - v0) >= 0.0f;
bool front1 = Vector2.Dot(n1, centerB - v1) >= 0.0f;
if (convex)
{
if (front0 || front1)
{
_limit11 = n1;
_limit12 = n0;
}
else
{
_limit11 = -n1;
_limit12 = -n0;
}
}
else
{
if (front0 && front1)
{
_limit11 = n0;
_limit12 = n1;
}
else
{
_limit11 = -n0;
_limit12 = -n1;
}
}
}
else
{
_limit11 = Vector2.Zero;
_limit12 = Vector2.Zero;
}
if (_edgeA.HasVertex3)
{
Vector2 e1 = v2 - v1;
Vector2 e2 = v3 - v2;
Vector2 n1 = new Vector2(e1.Y, -e1.X);
Vector2 n2 = new Vector2(e2.Y, -e2.X);
n1.Normalize();
n2.Normalize();
bool convex = MathUtils.Cross(n1, n2) >= 0.0f;
bool front1 = Vector2.Dot(n1, centerB - v1) >= 0.0f;
bool front2 = Vector2.Dot(n2, centerB - v2) >= 0.0f;
if (convex)
{
if (front1 || front2)
{
_limit21 = n2;
_limit22 = n1;
}
else
{
_limit21 = -n2;
_limit22 = -n1;
}
}
else
{
if (front1 && front2)
{
_limit21 = n1;
_limit22 = n2;
}
else
{
_limit21 = -n1;
_limit22 = -n2;
}
}
}
else
{
_limit21 = Vector2.Zero;
_limit22 = Vector2.Zero;
}
//ComputeAdjacency(); inline end
//EPAxis edgeAxis = ComputeEdgeSeparation(); inline start
EPAxis edgeAxis = ComputeEdgeSeparation();
// If no valid normal can be found than this edge should not collide.
// This can happen on the middle edge of a 3-edge zig-zag chain.
if (edgeAxis.Type == EPAxisType.Unknown)
{
return;
}
if (edgeAxis.Separation > _radius)
{
return;
}
EPAxis polygonAxis = ComputePolygonSeparation();
if (polygonAxis.Type != EPAxisType.Unknown && polygonAxis.Separation > _radius)
{
return;
}
// Use hysteresis for jitter reduction.
const float k_relativeTol = 0.98f;
const float k_absoluteTol = 0.001f;
EPAxis primaryAxis;
if (polygonAxis.Type == EPAxisType.Unknown)
{
primaryAxis = edgeAxis;
}
else if (polygonAxis.Separation > k_relativeTol * edgeAxis.Separation + k_absoluteTol)
{
primaryAxis = polygonAxis;
}
else
{
primaryAxis = edgeAxis;
}
EPProxy proxy1;
EPProxy proxy2;
FixedArray2<ClipVertex> incidentEdge = new FixedArray2<ClipVertex>();
if (primaryAxis.Type == EPAxisType.EdgeA)
{
proxy1 = _proxyA;
proxy2 = _proxyB;
manifold.Type = ManifoldType.FaceA;
}
else
{
proxy1 = _proxyB;
proxy2 = _proxyA;
manifold.Type = ManifoldType.FaceB;
}
int edge1 = primaryAxis.Index;
FindIncidentEdge(ref incidentEdge, proxy1, primaryAxis.Index, proxy2);
int count1 = proxy1.Count;
int iv1 = edge1;
int iv2 = edge1 + 1 < count1 ? edge1 + 1 : 0;
Vector2 v11 = proxy1.Vertices[iv1];
Vector2 v12 = proxy1.Vertices[iv2];
Vector2 tangent = v12 - v11;
tangent.Normalize();
Vector2 normal = MathUtils.Cross(tangent, 1.0f);
Vector2 planePoint = 0.5f * (v11 + v12);
// Face offset.
float frontOffset = Vector2.Dot(normal, v11);
// Side offsets, extended by polytope skin thickness.
float sideOffset1 = -Vector2.Dot(tangent, v11) + _radius;
float sideOffset2 = Vector2.Dot(tangent, v12) + _radius;
// Clip incident edge against extruded edge1 side edges.
FixedArray2<ClipVertex> clipPoints1;
FixedArray2<ClipVertex> clipPoints2;
int np;
// Clip to box side 1
np = ClipSegmentToLine(out clipPoints1, ref incidentEdge, -tangent, sideOffset1, iv1);
if (np < Settings.MaxManifoldPoints)
{
return;
}
// Clip to negative box side 1
np = ClipSegmentToLine(out clipPoints2, ref clipPoints1, tangent, sideOffset2, iv2);
if (np < Settings.MaxManifoldPoints)
{
return;
}
// Now clipPoints2 contains the clipped points.
if (primaryAxis.Type == EPAxisType.EdgeA)
{
manifold.LocalNormal = normal;
manifold.LocalPoint = planePoint;
}
else
{
manifold.LocalNormal = MathUtils.MultiplyT(ref _xf.R, ref normal);
manifold.LocalPoint = MathUtils.MultiplyT(ref _xf, ref planePoint);
}
int pointCount = 0;
for (int i1 = 0; i1 < Settings.MaxManifoldPoints; ++i1)
{
float separation = Vector2.Dot(normal, clipPoints2[i1].V) - frontOffset;
if (separation <= _radius)
{
ManifoldPoint cp = manifold.Points[pointCount];
if (primaryAxis.Type == EPAxisType.EdgeA)
{
cp.LocalPoint = MathUtils.MultiplyT(ref _xf, clipPoints2[i1].V);
cp.Id = clipPoints2[i1].ID;
}
else
{
cp.LocalPoint = clipPoints2[i1].V;
cp.Id.Features.TypeA = clipPoints2[i1].ID.Features.TypeB;
cp.Id.Features.TypeB = clipPoints2[i1].ID.Features.TypeA;
cp.Id.Features.IndexA = clipPoints2[i1].ID.Features.IndexB;
cp.Id.Features.IndexB = clipPoints2[i1].ID.Features.IndexA;
}
manifold.Points[pointCount] = cp;
++pointCount;
}
}
manifold.PointCount = pointCount;
//Collide(ref manifold); inline end
}
/// Compute the collision manifold between two circles.
public static void CollideCircles(ref Manifold manifold,
CircleShape circleA, ref Transform xfA,
CircleShape circleB, ref Transform xfB)
{
manifold.PointCount = 0;
float pAx = xfA.Position.X + xfA.R.Col1.X * circleA.Position.X + xfA.R.Col2.X * circleA.Position.Y;
float pAy = xfA.Position.Y + xfA.R.Col1.Y * circleA.Position.X + xfA.R.Col2.Y * circleA.Position.Y;
float pBx = xfB.Position.X + xfB.R.Col1.X * circleB.Position.X + xfB.R.Col2.X * circleB.Position.Y;
float pBy = xfB.Position.Y + xfB.R.Col1.Y * circleB.Position.X + xfB.R.Col2.Y * circleB.Position.Y;
float distSqr = (pBx - pAx) * (pBx - pAx) + (pBy - pAy) * (pBy - pAy);
float radius = circleA.Radius + circleB.Radius;
if (distSqr > radius * radius)
{
return;
}
manifold.Type = ManifoldType.Circles;
manifold.LocalPoint = circleA.Position;
manifold.LocalNormal = Vector2.Zero;
manifold.PointCount = 1;
ManifoldPoint p0 = manifold.Points[0];
p0.LocalPoint = circleB.Position;
p0.Id.Key = 0;
manifold.Points[0] = p0;
}
/// <summary>
/// Evaluate the manifold with supplied transforms. This assumes
/// modest motion from the original state. This does not change the
/// point count, impulses, etc. The radii must come from the Shapes
/// that generated the manifold.
/// </summary>
/// <param name="manifold">The manifold.</param>
/// <param name="transformA">The transform for A.</param>
/// <param name="radiusA">The radius for A.</param>
/// <param name="transformB">The transform for B.</param>
/// <param name="radiusB">The radius for B.</param>
/// <param name="normal">World vector pointing from A to B</param>
/// <param name="points">Torld contact point (point of intersection).</param>
public static void GetWorldManifold(ref Manifold manifold,
ref Transform transformA, float radiusA,
ref Transform transformB, float radiusB, out Vector2 normal,
out FixedArray2<Vector2> points)
{
points = new FixedArray2<Vector2>();
normal = Vector2.Zero;
if (manifold.PointCount == 0)
{
normal = Vector2.UnitY;
return;
}
switch (manifold.Type)
{
case ManifoldType.Circles:
{
Vector2 tmp = manifold.Points[0].LocalPoint;
float pointAx = transformA.Position.X + transformA.R.Col1.X * manifold.LocalPoint.X +
transformA.R.Col2.X * manifold.LocalPoint.Y;
float pointAy = transformA.Position.Y + transformA.R.Col1.Y * manifold.LocalPoint.X +
transformA.R.Col2.Y * manifold.LocalPoint.Y;
float pointBx = transformB.Position.X + transformB.R.Col1.X * tmp.X +
transformB.R.Col2.X * tmp.Y;
float pointBy = transformB.Position.Y + transformB.R.Col1.Y * tmp.X +
transformB.R.Col2.Y * tmp.Y;
normal.X = 1;
normal.Y = 0;
float result = (pointAx - pointBx) * (pointAx - pointBx) +
(pointAy - pointBy) * (pointAy - pointBy);
if (result > Settings.Epsilon * Settings.Epsilon)
{
float tmpNormalx = pointBx - pointAx;
float tmpNormaly = pointBy - pointAy;
float factor = 1f / (float)Math.Sqrt(tmpNormalx * tmpNormalx + tmpNormaly * tmpNormaly);
normal.X = tmpNormalx * factor;
normal.Y = tmpNormaly * factor;
}
Vector2 c = Vector2.Zero;
c.X = (pointAx + radiusA * normal.X) + (pointBx - radiusB * normal.X);
c.Y = (pointAy + radiusA * normal.Y) + (pointBy - radiusB * normal.Y);
points[0] = 0.5f * c;
}
break;
case ManifoldType.FaceA:
{
normal.X = transformA.R.Col1.X * manifold.LocalNormal.X +
transformA.R.Col2.X * manifold.LocalNormal.Y;
normal.Y = transformA.R.Col1.Y * manifold.LocalNormal.X +
transformA.R.Col2.Y * manifold.LocalNormal.Y;
float planePointx = transformA.Position.X + transformA.R.Col1.X * manifold.LocalPoint.X +
transformA.R.Col2.X * manifold.LocalPoint.Y;
float planePointy = transformA.Position.Y + transformA.R.Col1.Y * manifold.LocalPoint.X +
transformA.R.Col2.Y * manifold.LocalPoint.Y;
for (int i = 0; i < manifold.PointCount; ++i)
{
Vector2 tmp = manifold.Points[i].LocalPoint;
float clipPointx = transformB.Position.X + transformB.R.Col1.X * tmp.X +
transformB.R.Col2.X * tmp.Y;
float clipPointy = transformB.Position.Y + transformB.R.Col1.Y * tmp.X +
transformB.R.Col2.Y * tmp.Y;
float value = (clipPointx - planePointx) * normal.X + (clipPointy - planePointy) * normal.Y;
Vector2 c = Vector2.Zero;
c.X = (clipPointx + (radiusA - value) * normal.X) + (clipPointx - radiusB * normal.X);
c.Y = (clipPointy + (radiusA - value) * normal.Y) + (clipPointy - radiusB * normal.Y);
points[i] = 0.5f * c;
}
}
break;
case ManifoldType.FaceB:
{
normal.X = transformB.R.Col1.X * manifold.LocalNormal.X +
transformB.R.Col2.X * manifold.LocalNormal.Y;
normal.Y = transformB.R.Col1.Y * manifold.LocalNormal.X +
transformB.R.Col2.Y * manifold.LocalNormal.Y;
float planePointx = transformB.Position.X + transformB.R.Col1.X * manifold.LocalPoint.X +
transformB.R.Col2.X * manifold.LocalPoint.Y;
float planePointy = transformB.Position.Y + transformB.R.Col1.Y * manifold.LocalPoint.X +
transformB.R.Col2.Y * manifold.LocalPoint.Y;
for (int i = 0; i < manifold.PointCount; ++i)
{
Vector2 tmp = manifold.Points[i].LocalPoint;
float clipPointx = transformA.Position.X + transformA.R.Col1.X * tmp.X +
transformA.R.Col2.X * tmp.Y;
float clipPointy = transformA.Position.Y + transformA.R.Col1.Y * tmp.X +
transformA.R.Col2.Y * tmp.Y;
float value = (clipPointx - planePointx) * normal.X + (clipPointy - planePointy) * normal.Y;
Vector2 c = Vector2.Zero;
c.X = (clipPointx - radiusA * normal.X) + (clipPointx + (radiusB - value) * normal.X);
c.Y = (clipPointy - radiusA * normal.Y) + (clipPointy + (radiusB - value) * normal.Y);
points[i] = 0.5f * c;
}
// Ensure normal points from A to B.
normal *= -1;
}
break;
default:
normal = Vector2.UnitY;
break;
}
}
public static void GetPointStates(out FixedArray2<PointState> state1, out FixedArray2<PointState> state2,
ref Manifold manifold1, ref Manifold manifold2)
{
state1 = new FixedArray2<PointState>();
state2 = new FixedArray2<PointState>();
// Detect persists and removes.
for (int i = 0; i < manifold1.PointCount; ++i)
{
ContactID id = manifold1.Points[i].Id;
state1[i] = PointState.Remove;
for (int j = 0; j < manifold2.PointCount; ++j)
{
if (manifold2.Points[j].Id.Key == id.Key)
{
state1[i] = PointState.Persist;
break;
}
}
}
// Detect persists and adds.
for (int i = 0; i < manifold2.PointCount; ++i)
{
ContactID id = manifold2.Points[i].Id;
state2[i] = PointState.Add;
for (int j = 0; j < manifold1.PointCount; ++j)
{
if (manifold1.Points[j].Id.Key == id.Key)
{
state2[i] = PointState.Persist;
break;
}
}
}
}
/// <summary>
/// Compute the collision manifold between two polygons.
/// </summary>
/// <param name="manifold">The manifold.</param>
/// <param name="polyA">The poly A.</param>
/// <param name="transformA">The transform A.</param>
/// <param name="polyB">The poly B.</param>
/// <param name="transformB">The transform B.</param>
public static void CollidePolygons(ref Manifold manifold,
PolygonShape polyA, ref Transform transformA,
PolygonShape polyB, ref Transform transformB)
{
manifold.PointCount = 0;
float totalRadius = polyA.Radius + polyB.Radius;
int edgeA = 0;
float separationA = FindMaxSeparation(out edgeA, polyA, ref transformA, polyB, ref transformB);
if (separationA > totalRadius)
return;
int edgeB = 0;
float separationB = FindMaxSeparation(out edgeB, polyB, ref transformB, polyA, ref transformA);
if (separationB > totalRadius)
return;
PolygonShape poly1; // reference polygon
PolygonShape poly2; // incident polygon
Transform xf1, xf2;
int edge1; // reference edge
bool flip;
const float k_relativeTol = 0.98f;
const float k_absoluteTol = 0.001f;
if (separationB > k_relativeTol * separationA + k_absoluteTol)
{
poly1 = polyB;
poly2 = polyA;
xf1 = transformB;
xf2 = transformA;
edge1 = edgeB;
manifold.Type = ManifoldType.FaceB;
flip = true;
}
else
{
poly1 = polyA;
poly2 = polyB;
xf1 = transformA;
xf2 = transformB;
edge1 = edgeA;
manifold.Type = ManifoldType.FaceA;
flip = false;
}
FixedArray2<ClipVertex> incidentEdge;
FindIncidentEdge(out incidentEdge, poly1, ref xf1, edge1, poly2, ref xf2);
int count1 = poly1.Vertices.Count;
int iv1 = edge1;
int iv2 = edge1 + 1 < count1 ? edge1 + 1 : 0;
Vector2 v11 = poly1.Vertices[iv1];
Vector2 v12 = poly1.Vertices[iv2];
float localTangentX = v12.X - v11.X;
float localTangentY = v12.Y - v11.Y;
float factor = 1f / (float)Math.Sqrt(localTangentX * localTangentX + localTangentY * localTangentY);
localTangentX = localTangentX * factor;
localTangentY = localTangentY * factor;
Vector2 localNormal = new Vector2(localTangentY, -localTangentX);
Vector2 planePoint = 0.5f * (v11 + v12);
Vector2 tangent = new Vector2(xf1.R.Col1.X * localTangentX + xf1.R.Col2.X * localTangentY,
xf1.R.Col1.Y * localTangentX + xf1.R.Col2.Y * localTangentY);
float normalx = tangent.Y;
float normaly = -tangent.X;
v11 = new Vector2(xf1.Position.X + xf1.R.Col1.X * v11.X + xf1.R.Col2.X * v11.Y,
xf1.Position.Y + xf1.R.Col1.Y * v11.X + xf1.R.Col2.Y * v11.Y);
v12 = new Vector2(xf1.Position.X + xf1.R.Col1.X * v12.X + xf1.R.Col2.X * v12.Y,
xf1.Position.Y + xf1.R.Col1.Y * v12.X + xf1.R.Col2.Y * v12.Y);
// Face offset.
float frontOffset = normalx * v11.X + normaly * v11.Y;
// Side offsets, extended by polytope skin thickness.
float sideOffset1 = -(tangent.X * v11.X + tangent.Y * v11.Y) + totalRadius;
float sideOffset2 = tangent.X * v12.X + tangent.Y * v12.Y + totalRadius;
// Clip incident edge against extruded edge1 side edges.
FixedArray2<ClipVertex> clipPoints1;
FixedArray2<ClipVertex> clipPoints2;
// Clip to box side 1
int np = ClipSegmentToLine(out clipPoints1, ref incidentEdge, -tangent, sideOffset1, iv1);
if (np < 2)
return;
// Clip to negative box side 1
np = ClipSegmentToLine(out clipPoints2, ref clipPoints1, tangent, sideOffset2, iv2);
if (np < 2)
{
return;
}
// Now clipPoints2 contains the clipped points.
manifold.LocalNormal = localNormal;
manifold.LocalPoint = planePoint;
int pointCount = 0;
for (int i = 0; i < Settings.MaxManifoldPoints; ++i)
{
Vector2 value = clipPoints2[i].V;
float separation = normalx * value.X + normaly * value.Y - frontOffset;
if (separation <= totalRadius)
{
ManifoldPoint cp = manifold.Points[pointCount];
Vector2 tmp = clipPoints2[i].V;
float tmp1X = tmp.X - xf2.Position.X;
float tmp1Y = tmp.Y - xf2.Position.Y;
cp.LocalPoint.X = tmp1X * xf2.R.Col1.X + tmp1Y * xf2.R.Col1.Y;
cp.LocalPoint.Y = tmp1X * xf2.R.Col2.X + tmp1Y * xf2.R.Col2.Y;
cp.Id = clipPoints2[i].ID;
if (flip)
{
// Swap features
ContactFeature cf = cp.Id.Features;
cp.Id.Features.IndexA = cf.IndexB;
cp.Id.Features.IndexB = cf.IndexA;
cp.Id.Features.TypeA = cf.TypeB;
cp.Id.Features.TypeB = cf.TypeA;
}
manifold.Points[pointCount] = cp;
++pointCount;
}
}
manifold.PointCount = pointCount;
}
/// <summary>
/// Compute the collision manifold between a polygon and a circle.
/// </summary>
/// <param name="manifold">The manifold.</param>
/// <param name="polygonA">The polygon A.</param>
/// <param name="transformA">The transform of A.</param>
/// <param name="circleB">The circle B.</param>
/// <param name="transformB">The transform of B.</param>
public static void CollidePolygonAndCircle(ref Manifold manifold,
PolygonShape polygonA, ref Transform transformA,
CircleShape circleB, ref Transform transformB)
{
manifold.PointCount = 0;
// Compute circle position in the frame of the polygon.
Vector2 c =
new Vector2(
transformB.Position.X + transformB.R.Col1.X * circleB.Position.X +
transformB.R.Col2.X * circleB.Position.Y,
transformB.Position.Y + transformB.R.Col1.Y * circleB.Position.X +
transformB.R.Col2.Y * circleB.Position.Y);
Vector2 cLocal =
new Vector2(
(c.X - transformA.Position.X) * transformA.R.Col1.X +
(c.Y - transformA.Position.Y) * transformA.R.Col1.Y,
(c.X - transformA.Position.X) * transformA.R.Col2.X +
(c.Y - transformA.Position.Y) * transformA.R.Col2.Y);
// Find the min separating edge.
int normalIndex = 0;
float separation = -Settings.MaxFloat;
float radius = polygonA.Radius + circleB.Radius;
int vertexCount = polygonA.Vertices.Count;
for (int i = 0; i < vertexCount; ++i)
{
Vector2 value1 = polygonA.Normals[i];
Vector2 value2 = cLocal - polygonA.Vertices[i];
float s = value1.X * value2.X + value1.Y * value2.Y;
if (s > radius)
{
// Early out.
return;
}
if (s > separation)
{
separation = s;
normalIndex = i;
}
}
// Vertices that subtend the incident face.
int vertIndex1 = normalIndex;
int vertIndex2 = vertIndex1 + 1 < vertexCount ? vertIndex1 + 1 : 0;
Vector2 v1 = polygonA.Vertices[vertIndex1];
Vector2 v2 = polygonA.Vertices[vertIndex2];
// If the center is inside the polygon ...
if (separation < Settings.Epsilon)
{
manifold.PointCount = 1;
manifold.Type = ManifoldType.FaceA;
manifold.LocalNormal = polygonA.Normals[normalIndex];
manifold.LocalPoint = 0.5f * (v1 + v2);
ManifoldPoint p0 = manifold.Points[0];
p0.LocalPoint = circleB.Position;
p0.Id.Key = 0;
manifold.Points[0] = p0;
return;
}
// Compute barycentric coordinates
float u1 = (cLocal.X - v1.X) * (v2.X - v1.X) + (cLocal.Y - v1.Y) * (v2.Y - v1.Y);
float u2 = (cLocal.X - v2.X) * (v1.X - v2.X) + (cLocal.Y - v2.Y) * (v1.Y - v2.Y);
if (u1 <= 0.0f)
{
float r = (cLocal.X - v1.X) * (cLocal.X - v1.X) + (cLocal.Y - v1.Y) * (cLocal.Y - v1.Y);
if (r > radius * radius)
{
return;
}
manifold.PointCount = 1;
manifold.Type = ManifoldType.FaceA;
manifold.LocalNormal = cLocal - v1;
float factor = 1f /
(float)
Math.Sqrt(manifold.LocalNormal.X * manifold.LocalNormal.X +
manifold.LocalNormal.Y * manifold.LocalNormal.Y);
manifold.LocalNormal.X = manifold.LocalNormal.X * factor;
manifold.LocalNormal.Y = manifold.LocalNormal.Y * factor;
manifold.LocalPoint = v1;
ManifoldPoint p0b = manifold.Points[0];
p0b.LocalPoint = circleB.Position;
p0b.Id.Key = 0;
manifold.Points[0] = p0b;
}
else if (u2 <= 0.0f)
{
float r = (cLocal.X - v2.X) * (cLocal.X - v2.X) + (cLocal.Y - v2.Y) * (cLocal.Y - v2.Y);
if (r > radius * radius)
{
return;
}
manifold.PointCount = 1;
manifold.Type = ManifoldType.FaceA;
manifold.LocalNormal = cLocal - v2;
float factor = 1f /
(float)
Math.Sqrt(manifold.LocalNormal.X * manifold.LocalNormal.X +
manifold.LocalNormal.Y * manifold.LocalNormal.Y);
manifold.LocalNormal.X = manifold.LocalNormal.X * factor;
manifold.LocalNormal.Y = manifold.LocalNormal.Y * factor;
manifold.LocalPoint = v2;
ManifoldPoint p0c = manifold.Points[0];
p0c.LocalPoint = circleB.Position;
p0c.Id.Key = 0;
manifold.Points[0] = p0c;
}
else
{
Vector2 faceCenter = 0.5f * (v1 + v2);
Vector2 value1 = cLocal - faceCenter;
Vector2 value2 = polygonA.Normals[vertIndex1];
float separation2 = value1.X * value2.X + value1.Y * value2.Y;
if (separation2 > radius)
{
return;
}
manifold.PointCount = 1;
manifold.Type = ManifoldType.FaceA;
manifold.LocalNormal = polygonA.Normals[vertIndex1];
manifold.LocalPoint = faceCenter;
ManifoldPoint p0d = manifold.Points[0];
p0d.LocalPoint = circleB.Position;
p0d.Id.Key = 0;
manifold.Points[0] = p0d;
}
}