public void TestVerticalParallelLines()
{
Assert.IsFalse(
Line2Line2Collider.FindContacts(
Vector2.Zero, Vector2.UnitY,
Vector2.Zero, Vector2.UnitY
).HasContact
);
}
public void TestHorizontalParallelLines()
{
Assert.IsFalse(
Line2Line2Collider.FindContacts(
Vector2.Zero, Vector2.UnitX,
Vector2.Zero, Vector2.UnitX
).HasContact
);
}
public void TestDiagonallyCrossingLines()
{
LineContacts contacts = Line2Line2Collider.FindContacts(
new Vector2(1.0f, 0.0f), Vector2.Normalize(Vector2.One),
Vector2.Zero, Vector2.UnitY
);
float touchTime = -1.4142135623730950488016887242097f;
Assert.That(
contacts.EntryTime,
Is.EqualTo(touchTime).Within(Specifications.MaximumDeviation).Ulps
);
Assert.That(
contacts.ExitTime,
Is.EqualTo(touchTime).Within(Specifications.MaximumDeviation).Ulps
);
}
public void TestOrthogonallyCrossingLines()
{
LineContacts contacts = Line2Line2Collider.FindContacts(
new Vector2(-1.0f, 0.0f), Vector2.UnitX,
Vector2.Zero, Vector2.UnitY
);
float touchTime = 1.0f;
Assert.That(
contacts.EntryTime,
Is.EqualTo(touchTime).Within(Specifications.MaximumDeviation).Ulps
);
Assert.That(
contacts.ExitTime,
Is.EqualTo(touchTime).Within(Specifications.MaximumDeviation).Ulps
);
}
/// <summary>Determines where a ray will hit a line, if at all</summary>
/// <param name="rayStart">Starting point of the ray</param>
/// <param name="rayDirection">Direction into which the ray extends</param>
/// <param name="lineOffset">Offset of the line</param>
/// <param name="lineDirection">Direction along which the line extends</param>
/// <returns>The intersection points between the ray and the line, if any</returns>
public static LineContacts FindContacts(
Vector2 rayStart, Vector2 rayDirection,
Vector2 lineOffset, Vector2 lineDirection
)
{
LineContacts contacts = Line2Line2Collider.FindContacts(
rayStart, rayDirection, lineOffset, lineDirection
);
// If the contact occured before the starting offset of the ray,
// no collision took place since we're a ray
if (!float.IsNaN(contacts.EntryTime))
{
if (contacts.EntryTime < 0.0f)
{
return(LineContacts.None);
}
}
return(contacts);
}
/// <summary>Determines the contact location between a line and a triangle</summary>
/// <param name="lineOffset">
/// Offset of the line from the coordinate system's center
/// </param>
/// <param name="lineDirection">Direction and length of the line</param>
/// <param name="triangleA">
/// First corner point of triangle in counter-clockwise order
/// </param>
/// <param name="triangleB">
/// Second corner point of triangle in counter-clockwise order
/// </param>
/// <param name="triangleC">
/// Third corner point of triangle in counter-clockwise order
/// </param>
/// <returns>The point of intersection of the line with the triangle, if any</returns>
/// <remarks>
/// Everyone seems to know how to do 3D line / triangle intersections, but there
/// are no resources whatsoever on 2D line / triangle intersections. The code in here
/// is hand-written by myself. Instead of fancy math tricks, it simply tries to be
/// efficient using the existing code. It requires 4 line checks to find the accurate
/// intersection point with the triangle.
/// </remarks>
internal static LineContacts FindContacts(
Vector2 lineOffset, Vector2 lineDirection,
Vector2 triangleA, Vector2 triangleB, Vector2 triangleC
)
{
Vector2 ab = triangleB - triangleA;
Vector2 bc = triangleC - triangleB;
Vector2 ca = triangleA - triangleC;
float abLength = ab.Length();
float bcLength = bc.Length();
float caLength = ca.Length();
Vector2 abNormalized = ab / abLength;
Vector2 bcNormalized = bc / bcLength;
Vector2 caNormalized = ca / caLength;
LineContacts abContacts = Line2Line2Collider.FindContacts(
triangleA, abNormalized, lineOffset, lineDirection
);
LineContacts bcContacts = Line2Line2Collider.FindContacts(
triangleB, bcNormalized, lineOffset, lineDirection
);
// Does the line cross the A-B line of the triangle?
if (isWithin(abContacts, abLength))
{
abContacts = Line2Line2Collider.FindContacts(
lineOffset, lineDirection, triangleA, ab / abLength
);
// Find out which other line it crosses: B-C or C-A?
if (isWithin(bcContacts, bcLength))
{
bcContacts = Line2Line2Collider.FindContacts(
lineOffset, lineDirection, triangleB, bc / bcLength
);
}
else
{
bcContacts = Line2Line2Collider.FindContacts(
lineOffset, lineDirection, triangleC, ca / caLength
);
}
// Report the contacts in the right order
if (abContacts.EntryTime < bcContacts.EntryTime)
{
return(new LineContacts(abContacts.EntryTime, bcContacts.EntryTime));
}
else
{
return(new LineContacts(bcContacts.EntryTime, abContacts.EntryTime));
}
}
else if (isWithin(bcContacts, bcLength)) // Does is cross the B-C line?
{
bcContacts = Line2Line2Collider.FindContacts(
lineOffset, lineDirection, triangleB, bc / abLength
);
// We already checked A-B, so the other line it crosses must be C-A!
abContacts = Line2Line2Collider.FindContacts(
lineOffset, lineDirection, triangleC, ca / caLength
);
// Report the contacts in the right order
if (bcContacts.EntryTime < abContacts.EntryTime)
{
return(new LineContacts(bcContacts.EntryTime, abContacts.EntryTime));
}
else
{
return(new LineContacts(abContacts.EntryTime, bcContacts.EntryTime));
}
}
else // No contact on A-B or B-C, contact is impossible
{
return(LineContacts.None);
}
}
