/// <summary>
/// Intersection detection function
/// Mostly derived from http://www.codeproject.com/Articles/15573/2D-Polygon-Collision-Detection
/// </summary>
/// <param name="other">The other Body to check intersection with</param>
/// <returns>Vector2.Zero for no intersection, and minimum translation vector if there is an intersection</returns>
public override Vector2 Intersects(Polygon other)
{
//Separating Axis Theorem
int edgeCountA = this.Edges.Length;
int edgeCountB = other.Edges.Length;
float minIntervalDistance = 0;
Vector2 translationAxis = Vector2.Zero;
Vector2 edge;
for (int edgeIndex = 0; edgeIndex < edgeCountA + edgeCountB; edgeIndex++)
{
if (edgeIndex < edgeCountA)
{
edge = this.Edges[edgeIndex];
}
else
{
edge = other.Edges[edgeIndex - edgeCountA];
}
// ===== 1. Find if the polygons are currently intersecting =====
// Find the axis perpendicular to the current edge
Vector2 axis = new Vector2(-edge.Y, edge.X);
axis.Normalize();
// Find the projection of the polygon on the current axis
float minA = 0, minB = 0, maxA = 0, maxB = 0;
ProjectRectangle(axis, this, ref minA, ref maxA);
ProjectRectangle(axis, other, ref minB, ref maxB);
// Check if the polygon projections are currentlty intersecting
float intervalDistance = IntervalDistance(minA, maxA, minB, maxB);
if (intervalDistance > 0)
{
return Vector2.Zero;
}
// Check if the current interval distance is the minimum one. If so store
// the interval distance and the current distance.
// This will be used to calculate the minimum translation Vector2
if (intervalDistance > minIntervalDistance || minIntervalDistance == 0)
{
minIntervalDistance = intervalDistance;
translationAxis = axis;
Vector2 d = this.Position - other.Position;
if (d.X * translationAxis.X + d.Y * translationAxis.Y < 0)
translationAxis = -translationAxis;
}
}
//Console.WriteLine(minIntervalDistance);
return translationAxis * minIntervalDistance;
}
private void ApplyForce(float scale, Polygon player, Vector2 position, float deltaTime)
{
// Force drops off as 1/r for objects and 1/r^2 for players
foreach (Particle part in game.particles)
{
Vector2 dist = part.Position - position;
float length = dist.Length();
if (length != 0)
{
Vector2 force = scale * dist / (length * length);
if (force.LengthSquared() > GameData.MAX_FORCE)
{
force.Normalize();
force *= GameData.MAX_FORCE;
}
part.Velocity += force * deltaTime;
}
}
foreach (Drop drop in game.drops)
{
Vector2 dist = drop.Position - position;
float length = dist.Length();
if (length != 0)
{
Vector2 force = scale * dist / (length * length);
if (force.LengthSquared() > GameData.MAX_FORCE)
{
force.Normalize();
force *= GameData.MAX_FORCE;
}
drop.Velocity += force * deltaTime;
}
}
foreach (Player body in game.players)
{
if (body != player)
{
//Console.WriteLine(body.Velocity + "\t\t" + player.Velocity);
Vector2 dist = body.Position - position;
float length = dist.Length();
if (length != 0)
{
Vector2 force = scale * dist / (length * length);
if (force.Length() > GameData.MAX_FORCE)
{
force.Normalize();
force *= GameData.MAX_FORCE;
}
Console.WriteLine("Applying force: " + force);
body.Velocity += force * deltaTime; // 1/r for gravity
// User basically loses control if they are closer than the threshold
if (length < GameData.BOOMERANG_ANTIGRAV)
{
//if (force.X * body.Velocity.X > 0) // Velocity.X and force are in same direction
// body.TargetVelocity = body.Velocity.X;
body.Velocity.Y -= GameData.GRAVITY * deltaTime;
}
//Console.WriteLine("TargetVelocity: {0}", body.TargetVelocity);
}
}
}
}
private static void ProjectRectangle(Vector2 axis, Polygon body, ref float min, ref float max)
{
// Project a point on an axis using the dot product.
float dotProduct = axis.X * body.Points[0].X + axis.Y * body.Points[0].Y;
min = dotProduct;
max = dotProduct;
for (int i = 0; i < body.Points.Length; i++)
{
dotProduct = axis.X * body.Points[i].X + axis.Y * body.Points[i].Y;
if (dotProduct < min)
{
min = dotProduct;
}
else
{
if (dotProduct > max)
{
max = dotProduct;
}
}
}
}
/// <summary> /// Intersection detection function /// Mostly derived from http://www.codeproject.com/Articles/15573/2D-Polygon-Collision-Detection /// </summary> /// <param name="other">The other Body to check intersection with</param> /// <returns>Vector2.Zero for no intersection, and minimum translation vector if there is an intersection</returns> public abstract Vector2 Intersects(Polygon other);
