/// <summary>
/// Creates a chain.
/// </summary>
/// <param name="world">The world.</param>
/// <param name="start">The start.</param>
/// <param name="end">The end.</param>
/// <param name="linkWidth">The width.</param>
/// <param name="linkHeight">The height.</param>
/// <param name="fixStart">if set to <c>true</c> [fix start].</param>
/// <param name="fixEnd">if set to <c>true</c> [fix end].</param>
/// <param name="numberOfLinks">The number of links.</param>
/// <param name="linkDensity">The link density.</param>
/// <returns></returns>
public static Path CreateChain(World world, Vector2 start, Vector2 end, float linkWidth, float linkHeight,
bool fixStart, bool fixEnd, int numberOfLinks, float linkDensity)
{
//Chain start / end
Path path = new Path();
path.Add(start);
path.Add(end);
//A single chainlink
PolygonShape shape = new PolygonShape(PolygonTools.CreateRectangle(linkWidth, linkHeight), linkDensity);
//Use PathManager to create all the chainlinks based on the chainlink created before.
List<Body> chainLinks = PathManager.EvenlyDistributeShapesAlongPath(world, path, shape, BodyType.Dynamic,
numberOfLinks);
if (fixStart)
{
//Fix the first chainlink to the world
JointFactory.CreateFixedRevoluteJoint(world, chainLinks[0], new Vector2(0, -(linkHeight/2)),
chainLinks[0].Position);
}
if (fixEnd)
{
//Fix the last chainlink to the world
JointFactory.CreateFixedRevoluteJoint(world, chainLinks[chainLinks.Count - 1],
new Vector2(0, (linkHeight/2)),
chainLinks[chainLinks.Count - 1].Position);
}
//Attach all the chainlinks together with a revolute joint
PathManager.AttachBodiesWithRevoluteJoint(world, chainLinks, new Vector2(0, -linkHeight),
new Vector2(0, linkHeight),
false, false);
return (path);
}
/// <summary>
/// Special overload that takes in an existing body.
/// </summary>
/// <param name="width">The width.</param>
/// <param name="height">The height.</param>
/// <param name="density">The density.</param>
/// <param name="offset">The offset. The new shape is offset by this value</param>
/// <param name="body">The body.</param>
/// <returns></returns>
public static Fixture CreateRectangle(float width, float height, float density, Vector2 offset, Body body,
Object userData)
{
Vertices rectangleVertices = PolygonTools.CreateRectangle(width/2, height/2);
rectangleVertices.Translate(ref offset);
PolygonShape rectangleShape = new PolygonShape(rectangleVertices, density);
return body.CreateFixture(rectangleShape, userData);
}
public override Shape Clone()
{
PolygonShape clone = new PolygonShape();
clone.ShapeType = ShapeType;
clone.Radius = Radius;
if (Settings.ConserveMemory)
clone.Vertices = Vertices;
else
clone.Vertices = new Vertices(Vertices);
clone.Normals = Normals;
clone._density = _density;
clone.MassData = MassData;
return clone;
}
public static Fixture CreatePolygon(Vertices vertices, float density, Body body, Object userData)
{
if (vertices.Count <= 1)
throw new ArgumentOutOfRangeException("vertices", "Too few points to be a polygon");
PolygonShape polygon = new PolygonShape(vertices, density);
return body.CreateFixture(polygon, userData);
}
public static Fixture CreateRectangle(World world, float width, float height, float density, Vector2 position,
Object userData)
{
if (width <= 0)
throw new ArgumentOutOfRangeException("width", "Width must be more than 0 meters");
if (height <= 0)
throw new ArgumentOutOfRangeException("height", "Height must be more than 0 meters");
Body newBody = BodyFactory.CreateBody(world, position);
Vertices rectangleVertices = PolygonTools.CreateRectangle(width/2, height/2);
PolygonShape rectangleShape = new PolygonShape(rectangleVertices, density);
return newBody.CreateFixture(rectangleShape, userData);
}
public static List<Fixture> CreateCompoundPolygon(List<Vertices> list, float density, Body body, Object userData)
{
List<Fixture> fixtures = new List<Fixture>(list.Count);
//Then we create several fixtures using the body
foreach (Vertices vertices in list)
{
PolygonShape shape = new PolygonShape(vertices, density);
fixtures.Add(body.CreateFixture(shape, userData));
}
return fixtures;
}
public static Fixture CreateEllipse(float xRadius, float yRadius, int edges, float density, Body body,
Object userData)
{
if (xRadius <= 0)
throw new ArgumentOutOfRangeException("xRadius", "X-radius must be more than 0");
if (yRadius <= 0)
throw new ArgumentOutOfRangeException("yRadius", "Y-radius must be more than 0");
Vertices ellipseVertices = PolygonTools.CreateEllipse(xRadius, yRadius, edges);
PolygonShape polygonShape = new PolygonShape(ellipseVertices, density);
return body.CreateFixture(polygonShape, userData);
}
/// <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
}
public BreakableBody(IEnumerable<Vertices> vertices, World world, float density, Object userData)
{
_world = world;
_world.ContactManager.PostSolve += PostSolve;
MainBody = new Body(_world);
MainBody.BodyType = BodyType.Dynamic;
foreach (Vertices part in vertices)
{
PolygonShape polygonShape = new PolygonShape(part, density);
Fixture fixture = MainBody.CreateFixture(polygonShape, userData);
Parts.Add(fixture);
}
}
/// <summary>
/// Find the max separation between poly1 and poly2 using edge normals from poly1.
/// </summary>
/// <param name="edgeIndex">Index of the edge.</param>
/// <param name="poly1">The poly1.</param>
/// <param name="xf1">The XF1.</param>
/// <param name="poly2">The poly2.</param>
/// <param name="xf2">The XF2.</param>
/// <returns></returns>
private static float FindMaxSeparation(out int edgeIndex,
PolygonShape poly1, ref Transform xf1,
PolygonShape poly2, ref Transform xf2)
{
int count1 = poly1.Vertices.Count;
// Vector pointing from the centroid of poly1 to the centroid of poly2.
float dx = (xf2.Position.X + xf2.R.Col1.X*poly2.MassData.Centroid.X + xf2.R.Col2.X*poly2.MassData.Centroid.Y) -
(xf1.Position.X + xf1.R.Col1.X*poly1.MassData.Centroid.X + xf1.R.Col2.X*poly1.MassData.Centroid.Y);
float dy = (xf2.Position.Y + xf2.R.Col1.Y*poly2.MassData.Centroid.X + xf2.R.Col2.Y*poly2.MassData.Centroid.Y) -
(xf1.Position.Y + xf1.R.Col1.Y*poly1.MassData.Centroid.X + xf1.R.Col2.Y*poly1.MassData.Centroid.Y);
Vector2 dLocal1 = new Vector2(dx*xf1.R.Col1.X + dy*xf1.R.Col1.Y, dx*xf1.R.Col2.X + dy*xf1.R.Col2.Y);
// Find edge normal on poly1 that has the largest projection onto d.
int edge = 0;
float maxDot = -Settings.MaxFloat;
for (int i = 0; i < count1; ++i)
{
float dot = Vector2.Dot(poly1.Normals[i], dLocal1);
if (dot > maxDot)
{
maxDot = dot;
edge = i;
}
}
// Get the separation for the edge normal.
float s = EdgeSeparation(poly1, ref xf1, edge, poly2, ref xf2);
// Check the separation for the previous edge normal.
int prevEdge = edge - 1 >= 0 ? edge - 1 : count1 - 1;
float sPrev = EdgeSeparation(poly1, ref xf1, prevEdge, poly2, ref xf2);
// Check the separation for the next edge normal.
int nextEdge = edge + 1 < count1 ? edge + 1 : 0;
float sNext = EdgeSeparation(poly1, ref xf1, nextEdge, poly2, ref xf2);
// Find the best edge and the search direction.
int bestEdge;
float bestSeparation;
int increment;
if (sPrev > s && sPrev > sNext)
{
increment = -1;
bestEdge = prevEdge;
bestSeparation = sPrev;
}
else if (sNext > s)
{
increment = 1;
bestEdge = nextEdge;
bestSeparation = sNext;
}
else
{
edgeIndex = edge;
return s;
}
// Perform a local search for the best edge normal.
for (;;)
{
if (increment == -1)
edge = bestEdge - 1 >= 0 ? bestEdge - 1 : count1 - 1;
else
edge = bestEdge + 1 < count1 ? bestEdge + 1 : 0;
s = EdgeSeparation(poly1, ref xf1, edge, poly2, ref xf2);
if (s > bestSeparation)
{
bestEdge = edge;
bestSeparation = s;
}
else
{
break;
}
}
edgeIndex = bestEdge;
return bestSeparation;
}
private static void FindIncidentEdge(out FixedArray2<ClipVertex> c,
PolygonShape poly1, ref Transform xf1, int edge1,
PolygonShape poly2, ref Transform xf2)
{
c = new FixedArray2<ClipVertex>();
int count2 = poly2.Vertices.Count;
Debug.Assert(0 <= edge1 && edge1 < poly1.Vertices.Count);
// Get the normal of the reference edge in poly2's frame.
Vector2 v = poly1.Normals[edge1];
float tmpx = xf1.R.Col1.X*v.X + xf1.R.Col2.X*v.Y;
float tmpy = xf1.R.Col1.Y*v.X + xf1.R.Col2.Y*v.Y;
Vector2 normal1 = new Vector2(tmpx*xf2.R.Col1.X + tmpy*xf2.R.Col1.Y, tmpx*xf2.R.Col2.X + tmpy*xf2.R.Col2.Y);
// Find the incident edge on poly2.
int index = 0;
float minDot = Settings.MaxFloat;
for (int i = 0; i < count2; ++i)
{
float dot = Vector2.Dot(normal1, poly2.Normals[i]);
if (dot < minDot)
{
minDot = dot;
index = i;
}
}
// Build the clip vertices for the incident edge.
int i1 = index;
int i2 = i1 + 1 < count2 ? i1 + 1 : 0;
ClipVertex cv0 = c[0];
Vector2 v1 = poly2.Vertices[i1];
cv0.V.X = xf2.Position.X + xf2.R.Col1.X*v1.X + xf2.R.Col2.X*v1.Y;
cv0.V.Y = xf2.Position.Y + xf2.R.Col1.Y*v1.X + xf2.R.Col2.Y*v1.Y;
cv0.ID.Features.IndexA = (byte) edge1;
cv0.ID.Features.IndexB = (byte) i1;
cv0.ID.Features.TypeA = (byte) ContactFeatureType.Face;
cv0.ID.Features.TypeB = (byte) ContactFeatureType.Vertex;
c[0] = cv0;
ClipVertex cv1 = c[1];
Vector2 v2 = poly2.Vertices[i2];
cv1.V.X = xf2.Position.X + xf2.R.Col1.X*v2.X + xf2.R.Col2.X*v2.Y;
cv1.V.Y = xf2.Position.Y + xf2.R.Col1.Y*v2.X + xf2.R.Col2.Y*v2.Y;
cv1.ID.Features.IndexA = (byte) edge1;
cv1.ID.Features.IndexB = (byte) i2;
cv1.ID.Features.TypeA = (byte) ContactFeatureType.Face;
cv1.ID.Features.TypeB = (byte) ContactFeatureType.Vertex;
c[1] = cv1;
}
/// <summary>
/// Find the separation between poly1 and poly2 for a give edge normal on poly1.
/// </summary>
/// <param name="poly1">The poly1.</param>
/// <param name="xf1">The XF1.</param>
/// <param name="edge1">The edge1.</param>
/// <param name="poly2">The poly2.</param>
/// <param name="xf2">The XF2.</param>
/// <returns></returns>
private static float EdgeSeparation(PolygonShape poly1, ref Transform xf1, int edge1,
PolygonShape poly2, ref Transform xf2)
{
int count2 = poly2.Vertices.Count;
Debug.Assert(0 <= edge1 && edge1 < poly1.Vertices.Count);
// Convert normal from poly1's frame into poly2's frame.
Vector2 p1n = poly1.Normals[edge1];
float normalWorldx = xf1.R.Col1.X*p1n.X + xf1.R.Col2.X*p1n.Y;
float normalWorldy = xf1.R.Col1.Y*p1n.X + xf1.R.Col2.Y*p1n.Y;
Vector2 normal = new Vector2(normalWorldx*xf2.R.Col1.X + normalWorldy*xf2.R.Col1.Y,
normalWorldx*xf2.R.Col2.X + normalWorldy*xf2.R.Col2.Y);
// Find support vertex on poly2 for -normal.
int index = 0;
float minDot = Settings.MaxFloat;
for (int i = 0; i < count2; ++i)
{
float dot = Vector2.Dot(poly2.Vertices[i], normal);
if (dot < minDot)
{
minDot = dot;
index = i;
}
}
Vector2 p1ve = poly1.Vertices[edge1];
Vector2 p2vi = poly2.Vertices[index];
return ((xf2.Position.X + xf2.R.Col1.X*p2vi.X + xf2.R.Col2.X*p2vi.Y) -
(xf1.Position.X + xf1.R.Col1.X*p1ve.X + xf1.R.Col2.X*p1ve.Y))*normalWorldx +
((xf2.Position.Y + xf2.R.Col1.Y*p2vi.X + xf2.R.Col2.Y*p2vi.Y) -
(xf1.Position.Y + xf1.R.Col1.Y*p1ve.X + xf1.R.Col2.Y*p1ve.Y))*normalWorldy;
}
/// <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;
}
}
