/// <summary>
/// Test one axis with SAT.
/// Updates result if there is a "better" hit
/// </summary>
private static void testAxis(Projection prj1, Projection prj2, Vector relativeVelocity, Vector axis, CollisionResult result, double remainingFrameFraction, int axisOwner)
{
bool isIntersecting = false, willIntersect = false;
double t = 0; //Collision time
//Positive distance means we don't have an overlap. Negative means we have an overlap.
double distance = prj1.GetDistance(prj2);
#if DEBUG_COLLISION_OBJECT_POLYGON || DEBUG_COLLISION_OBJECT_OBJECT
Log.Write("\tTesting axis " + axis + ", relative vel: " + relativeVelocity, Log.DEBUG);
Log.Write("\tProjection 1: " + prj1 + " Projection 2: " + prj2, Log.DEBUG);
Log.Write("\tDistance " + distance, Log.DEBUG);
#endif
//Already intersecting?
if (distance < 0)
{
isIntersecting = true;
#if DEBUG_COLLISION_OBJECT_POLYGON || DEBUG_COLLISION_OBJECT_OBJECT
Log.Write("\tIntersecting.", Log.DEBUG);
#endif
}
else
{
//Calculate velocity component in direction of axis
double velAxis = axis.DotProduct(relativeVelocity);
//if (velAxis < Constants.MinDouble) velAxis = 0;
#if DEBUG_COLLISION_OBJECT_POLYGON || DEBUG_COLLISION_OBJECT_OBJECT
Log.Write("\tNot intersecting. Velocity along axis: " + velAxis, Log.DEBUG);
#endif
//If projection of polygon 2 is to the right of polygon 1, AND we have a positive velocity along the axis
//OR projection of polygon 1 is to the left of polygon 2 AND we have a negative velocity along axis
//then we might have a collision in the future. If not, the objects are either moving in separate directions
//or they are staying still.
if ((velAxis > 0 && prj2.Min >= prj1.Max) || (velAxis < 0 && prj1.Min >= prj2.Max))
{
//If the axis belongs to object 1, and it's facing the opposite direction of the velocity,
//then ignore it because it can't collide. Also, if the axis belongs to object 2,
//and the axis faces the same direction as the velocity, also ignore it.
#if DEBUG_COLLISION_OBJECT_POLYGON
Log.Write("\tAxis dot Velocity: " + axis.DotProduct(relativeVelocity) * (axisOwner == 0 ? -1 : 1) + " Axis: " + axis, Log.DEBUG);
#endif
//Ignore this test if the axis faces the wrong way
if (axis.DotProduct(relativeVelocity) * (axisOwner == 0 ? -1 : 1) > Constants.MinDouble)
{
#if DEBUG_COLLISION_OBJECT_POLYGON || DEBUG_COLLISION_OBJECT_OBJECT
Log.Write("\tIgnoring test because the edge faces the wrong way. Dot: " + axis.DotProduct(relativeVelocity) * (axisOwner == 0 ? -1 : 1) + "Owner: " + axisOwner);
#endif
distance = double.NegativeInfinity;
isIntersecting = true;
}
else
{
t = distance / Math.Abs(velAxis);
if (t < remainingFrameFraction)
willIntersect = true;
#if DEBUG_COLLISION_OBJECT_POLYGON || DEBUG_COLLISION_OBJECT_OBJECT
Log.Write("\tCollision time: " + t, Log.DEBUG);
#endif
}
}
#if DEBUG_COLLISION_OBJECT_POLYGON || DEBUG_COLLISION_OBJECT_OBJECT
else
{
Log.Write("\tMoving the wrong way. No collision.", Log.DEBUG);
}
#endif
}
//Find the "best" guess of HOW the objects collides.
//That is, what direction, and what normal was intersected first.
if ((!result.isIntersecting && !result.hasIntersected) || //If the result intersection flags are both false, this is the first test.
(result.isIntersecting && (willIntersect || (isIntersecting && result.distance < distance))) || //Previous result was an overlapping one, while the latest result indicate o1 and o2 will collide in the future instead,
(result.hasIntersected && willIntersect && t > result.collisionTime)) //Previous result was that o1 and o2 collides in the future, but this result indicates that they collide later.
{
result.isIntersecting = isIntersecting;
result.hasIntersected = willIntersect;
result.collisionTime = t;
result.distance = distance;
result.hitNormal = axis;
#if DEBUG_COLLISION_OBJECT_POLYGON || DEBUG_COLLISION_OBJECT_OBJECT
Log.Write("\tNew best axis", Log.DEBUG);
#endif
}
//No intersection now or in the future.
else if (!isIntersecting && !willIntersect)
{
result.hasIntersected = false;
result.isIntersecting = false;
}
}