/// <summary>
/// Checks two shapes for collisions.
/// </summary>
/// <param name="support1">The SupportMappable implementation of the first shape to test.</param>
/// <param name="support2">The SupportMappable implementation of the seconds shape to test.</param>
/// <param name="orientation1">The orientation of the first shape.</param>
/// <param name="orientation2">The orientation of the second shape.</param>
/// <param name="position1">The position of the first shape.</param>
/// <param name="position2">The position of the second shape</param>
/// <param name="point">The pointin world coordinates, where collision occur.</param>
/// <param name="normal">The normal pointing from body2 to body1.</param>
/// <param name="penetration">Estimated penetration depth of the collision.</param>
/// <returns>Returns true if there is a collision, false otherwise.</returns>
public static bool Detect(ISupportMappable support1, ISupportMappable support2, ref JMatrix orientation1,
ref JMatrix orientation2, ref JVector position1, ref JVector position2,
out JVector point, out JVector normal, out float penetration)
{
// Used variables
JVector temp1, temp2;
JVector v01, v02, v0;
JVector v11, v12, v1;
JVector v21, v22, v2;
JVector v31, v32, v3;
JVector v41, v42, v4;
JVector mn;
// Initialization of the output
point = normal = JVector.Zero;
penetration = 0.0f;
//JVector right = JVector.Right;
// Get the center of shape1 in world coordinates -> v01
support1.SupportCenter(out v01);
JVector.Transform(ref v01, ref orientation1, out v01);
JVector.Add(ref position1, ref v01, out v01);
// Get the center of shape2 in world coordinates -> v02
support2.SupportCenter(out v02);
JVector.Transform(ref v02, ref orientation2, out v02);
JVector.Add(ref position2, ref v02, out v02);
// v0 is the center of the minkowski difference
JVector.Subtract(ref v02, ref v01, out v0);
// Avoid case where centers overlap -- any direction is fine in this case
if (v0.IsNearlyZero())
{
v0 = new JVector(0.00001f, 0, 0);
}
// v1 = support in direction of origin
mn = v0;
JVector.Negate(ref v0, out normal);
SupportMapTransformed(support1, ref orientation1, ref position1, ref mn, out v11);
SupportMapTransformed(support2, ref orientation2, ref position2, ref normal, out v12);
JVector.Subtract(ref v12, ref v11, out v1);
if (JVector.Dot(ref v1, ref normal) <= 0.0f)
{
return(false);
}
// v2 = support perpendicular to v1,v0
JVector.Cross(ref v1, ref v0, out normal);
if (normal.IsNearlyZero())
{
JVector.Subtract(ref v1, ref v0, out normal);
normal.Normalize();
point = v11;
JVector.Add(ref point, ref v12, out point);
JVector.Multiply(ref point, 0.5f, out point);
JVector.Subtract(ref v12, ref v11, out temp1);
penetration = JVector.Dot(ref temp1, ref normal);
//point = v11;
//point2 = v12;
return(true);
}
JVector.Negate(ref normal, out mn);
SupportMapTransformed(support1, ref orientation1, ref position1, ref mn, out v21);
SupportMapTransformed(support2, ref orientation2, ref position2, ref normal, out v22);
JVector.Subtract(ref v22, ref v21, out v2);
if (JVector.Dot(ref v2, ref normal) <= 0.0f)
{
return(false);
}
// Determine whether origin is on + or - side of plane (v1,v0,v2)
JVector.Subtract(ref v1, ref v0, out temp1);
JVector.Subtract(ref v2, ref v0, out temp2);
JVector.Cross(ref temp1, ref temp2, out normal);
float dist = JVector.Dot(ref normal, ref v0);
// If the origin is on the - side of the plane, reverse the direction of the plane
if (dist > 0.0f)
{
JVector.Swap(ref v1, ref v2);
JVector.Swap(ref v11, ref v21);
JVector.Swap(ref v12, ref v22);
JVector.Negate(ref normal, out normal);
}
int phase2 = 0;
int phase1 = 0;
bool hit = false;
// Phase One: Identify a portal
while (true)
{
if (phase1 > MaximumIterations)
{
return(false);
}
phase1++;
// Obtain the support point in a direction perpendicular to the existing plane
// Note: This point is guaranteed to lie off the plane
JVector.Negate(ref normal, out mn);
SupportMapTransformed(support1, ref orientation1, ref position1, ref mn, out v31);
SupportMapTransformed(support2, ref orientation2, ref position2, ref normal, out v32);
JVector.Subtract(ref v32, ref v31, out v3);
if (JVector.Dot(ref v3, ref normal) <= 0.0f)
{
return(false);
}
// If origin is outside (v1,v0,v3), then eliminate v2 and loop
JVector.Cross(ref v1, ref v3, out temp1);
if (JVector.Dot(ref temp1, ref v0) < 0.0f)
{
v2 = v3;
v21 = v31;
v22 = v32;
JVector.Subtract(ref v1, ref v0, out temp1);
JVector.Subtract(ref v3, ref v0, out temp2);
JVector.Cross(ref temp1, ref temp2, out normal);
continue;
}
// If origin is outside (v3,v0,v2), then eliminate v1 and loop
JVector.Cross(ref v3, ref v2, out temp1);
if (JVector.Dot(ref temp1, ref v0) < 0.0f)
{
v1 = v3;
v11 = v31;
v12 = v32;
JVector.Subtract(ref v3, ref v0, out temp1);
JVector.Subtract(ref v2, ref v0, out temp2);
JVector.Cross(ref temp1, ref temp2, out normal);
continue;
}
// Phase Two: Refine the portal
// We are now inside of a wedge...
while (true)
{
phase2++;
// Compute normal of the wedge face
JVector.Subtract(ref v2, ref v1, out temp1);
JVector.Subtract(ref v3, ref v1, out temp2);
JVector.Cross(ref temp1, ref temp2, out normal);
// Can this happen??? Can it be handled more cleanly?
if (normal.IsNearlyZero())
{
return(true);
}
normal.Normalize();
// Compute distance from origin to wedge face
float d = JVector.Dot(ref normal, ref v1);
// If the origin is inside the wedge, we have a hit
if (d >= 0 && !hit)
{
// HIT!!!
hit = true;
}
// Find the support point in the direction of the wedge face
JVector.Negate(ref normal, out mn);
SupportMapTransformed(support1, ref orientation1, ref position1, ref mn, out v41);
SupportMapTransformed(support2, ref orientation2, ref position2, ref normal, out v42);
JVector.Subtract(ref v42, ref v41, out v4);
JVector.Subtract(ref v4, ref v3, out temp1);
float delta = JVector.Dot(ref temp1, ref normal);
penetration = JVector.Dot(ref v4, ref normal);
// If the boundary is thin enough or the origin is outside the support plane for the newly discovered vertex, then we can terminate
if (delta <= CollideEpsilon || penetration <= 0.0f || phase2 > MaximumIterations)
{
if (hit)
{
JVector.Cross(ref v1, ref v2, out temp1);
float b0 = JVector.Dot(ref temp1, ref v3);
JVector.Cross(ref v3, ref v2, out temp1);
float b1 = JVector.Dot(ref temp1, ref v0);
JVector.Cross(ref v0, ref v1, out temp1);
float b2 = JVector.Dot(ref temp1, ref v3);
JVector.Cross(ref v2, ref v1, out temp1);
float b3 = JVector.Dot(ref temp1, ref v0);
float sum = b0 + b1 + b2 + b3;
if (sum <= 0)
{
b0 = 0;
JVector.Cross(ref v2, ref v3, out temp1);
b1 = JVector.Dot(ref temp1, ref normal);
JVector.Cross(ref v3, ref v1, out temp1);
b2 = JVector.Dot(ref temp1, ref normal);
JVector.Cross(ref v1, ref v2, out temp1);
b3 = JVector.Dot(ref temp1, ref normal);
sum = b1 + b2 + b3;
}
float inv = 1.0f / sum;
JVector.Multiply(ref v01, b0, out point);
JVector.Multiply(ref v11, b1, out temp1);
JVector.Add(ref point, ref temp1, out point);
JVector.Multiply(ref v21, b2, out temp1);
JVector.Add(ref point, ref temp1, out point);
JVector.Multiply(ref v31, b3, out temp1);
JVector.Add(ref point, ref temp1, out point);
JVector.Multiply(ref v02, b0, out temp2);
JVector.Add(ref temp2, ref point, out point);
JVector.Multiply(ref v12, b1, out temp1);
JVector.Add(ref point, ref temp1, out point);
JVector.Multiply(ref v22, b2, out temp1);
JVector.Add(ref point, ref temp1, out point);
JVector.Multiply(ref v32, b3, out temp1);
JVector.Add(ref point, ref temp1, out point);
JVector.Multiply(ref point, inv * 0.5f, out point);
}
// Compute the barycentric coordinates of the origin
return(hit);
}
////// Compute the tetrahedron dividing face (v4,v0,v1)
//JVector.Cross(ref v4, ref v1, out temp1);
//float d1 = JVector.Dot(ref temp1, ref v0);
////// Compute the tetrahedron dividing face (v4,v0,v2)
//JVector.Cross(ref v4, ref v2, out temp1);
//float d2 = JVector.Dot(ref temp1, ref v0);
// Compute the tetrahedron dividing face (v4,v0,v3)
JVector.Cross(ref v4, ref v0, out temp1);
float dot = JVector.Dot(ref temp1, ref v1);
if (dot >= 0.0f)
{
dot = JVector.Dot(ref temp1, ref v2);
if (dot >= 0.0f)
{
// Inside d1 & inside d2 ==> eliminate v1
v1 = v4;
v11 = v41;
v12 = v42;
}
else
{
// Inside d1 & outside d2 ==> eliminate v3
v3 = v4;
v31 = v41;
v32 = v42;
}
}
else
{
dot = JVector.Dot(ref temp1, ref v3);
if (dot >= 0.0f)
{
// Outside d1 & inside d3 ==> eliminate v2
v2 = v4;
v21 = v41;
v22 = v42;
}
else
{
// Outside d1 & outside d3 ==> eliminate v1
v1 = v4;
v11 = v41;
v12 = v42;
}
}
}
}
}
/// <summary>
/// Discrete Box vs Box test. Very fast. Generates contact info. NOTE: ensure UpdateAxes is called for each BoxShape prior.
/// </summary>
/// <param name="A">BoxShape A.</param>
/// <param name="PA">BoxShape A's position.</param>
/// <param name="OA">BoxShape A's orientation.</param>
/// <param name="B">BoxShape B.</param>
/// <param name="PB">BoxShape B's position.</param>
/// <param name="OB">BoxShape B's orientation.</param>
/// <param name="normal">Normal of collision.</param>
/// <param name="t">Amount of penetration.</param>
/// <param name="CA">Contacts found on BoxShape A.</param>
/// <param name="CB">Contacts found on BoxShape B.</param>
/// <param name="NumContacts">Number of contacts found.</param>
/// <returns>True if collision exists.</returns>
public static bool BoxBoxTestContact(ref BoxShape A, ref JVector PA, ref JMatrix OA,
ref BoxShape B, ref JVector PB, ref JMatrix OB,
out JVector normal, out float t, out JVector[] CA, out JVector[] CB, out int NumContacts)
{
float overlap = 0;
normal = A.xAxis;
t = 0.0f;
// TODO in future to save a few bytes of garbage make these
// SA1, SA2 and SB1, SB2 (no arrays)
JVector[] SA = new JVector[2], SB = new JVector[2];
int NumSA = 0, NumSB = 0;
CA = new JVector[2]; CB = new JVector[2];
NumContacts = 0;
JVector T = PB - PA;
// cache scaled local axes
JVector Ax = A.halfSize.X * A.xAxis;
JVector Ay = A.halfSize.Y * A.yAxis;
JVector Bx = B.halfSize.X * B.xAxis;
JVector By = B.halfSize.Y * B.yAxis;
// axis to test
JVector L = A.xAxis;
float TL = Math.Abs(T * L);
float a = Math.Abs((Ax) * L) + Math.Abs((Ay) * L);
float b = Math.Abs((Bx) * L) + Math.Abs((By) * L);
if (TL > (a + b))
{
return(false);
}
// cache overlap
// just set first overlap
overlap = TL - (b + a);
// axis to test
L = A.yAxis;
TL = Math.Abs(T * L);
a = Math.Abs((Ax) * L) + Math.Abs((Ay) * L);
b = Math.Abs((Bx) * L) + Math.Abs((By) * L);
if (TL > (a + b))
{
return(false);
}
// cache overlap
var o = TL - (b + a);
if (o > overlap)
{
overlap = o;
normal = A.yAxis;
}
// axis to test
L = B.xAxis;
TL = Math.Abs(T * L);
a = Math.Abs((Ax) * L) + Math.Abs((Ay) * L);
b = Math.Abs((Bx) * L) + Math.Abs((By) * L);
if (TL > (a + b))
{
return(false);
}
// cache overlap
o = TL - (b + a);
if (o > overlap)
{
overlap = o;
normal = B.xAxis;
}
// axis to test
L = B.yAxis;
TL = Math.Abs(T * L);
a = Math.Abs((Ax) * L) + Math.Abs((Ay) * L);
b = Math.Abs((Bx) * L) + Math.Abs((By) * L);
if (TL > (a + b))
{
return(false);
}
// cache overlap
o = TL - (b + a);
if (o > overlap)
{
overlap = o;
normal = B.yAxis;
}
// make sure the polygons gets pushed away from each other.
if (normal * T < 0.0f)
{
normal = -normal;
}
t = overlap;
// now to find a contact point or edge!
var mn = -normal;
NumSA = A.FindSupportPoints(ref mn, ref PA, ref OA, out SA);
NumSB = B.FindSupportPoints(ref normal, ref PB, ref OB, out SB);
// now refine contact points from support points
// edge/vertex case
if (NumSA == 2 && NumSB == 1)
{
ProjectPointOnLine(ref SB[0], ref SA[0], ref SA[1], out CA[NumContacts]);
CB[NumContacts] = SB[0];
NumContacts++;
return(true);
}
// vertex/edge case
if (NumSA == 1 && NumSB == 2)
{
ProjectPointOnLine(ref SA[0], ref SB[0], ref SB[1], out CB[NumContacts]);
CA[NumContacts] = SA[0];
NumContacts++;
return(true);
}
// edge/edge case
if (NumSA == 2 && NumSB == 2)
{
// clip contacts
JVector perp = new JVector(-normal.Y, normal.X);
// project first 2 contacts to axis perpendicular to normal
float min0 = SA[0] * perp;
float max0 = min0;
float min1 = SB[0] * perp;
float max1 = min1;
// project next point from A
max0 = SA[1] * perp;
if (max0 < min0)
{
JMath.Swapf(ref min0, ref max0);
JVector.Swap(ref SA[0], ref SA[1]);
}
max1 = SB[1] * perp;
if (max1 < min1)
{
JMath.Swapf(ref min1, ref max1);
JVector.Swap(ref SB[0], ref SB[1]);
}
if (min0 > min1)
{
JVector Pseg;
ProjectPointOnLine(ref SA[0], ref SB[0], ref SB[1], out Pseg);
CA[NumContacts] = SA[0];
CB[NumContacts] = Pseg;
NumContacts++;
}
else
{
JVector Pseg;
ProjectPointOnLine(ref SB[0], ref SA[0], ref SA[1], out Pseg);
CA[NumContacts] = Pseg;
CB[NumContacts] = SB[0];
NumContacts++;
}
if (max0 < max1)
{
JVector Pseg;
ProjectPointOnLine(ref SA[1], ref SB[0], ref SB[1], out Pseg);
CA[NumContacts] = SA[1];
CB[NumContacts] = Pseg;
NumContacts++;
}
else
{
JVector Pseg;
ProjectPointOnLine(ref SB[1], ref SA[0], ref SA[1], out Pseg);
CA[NumContacts] = Pseg;
CB[NumContacts] = SB[1];
NumContacts++;
}
return(true);
}
// if all axes overlap collision exists
return(true);
}