public Polygon(Polygon p)
{
foreach (Vector2 point in p.Points)
{
m_Points.Add(point);
}
BuildEdges();
CalculateMaxMin();
}
/// <summary>
/// The default Constructor.
/// </summary>
public Camera(float prefWidth, float prefHeight, float windowWidth, float windowHeight, MouseDevice m)
{
OriginalBounds = CameraBounds = new Polygon();
TargetScale = Scale = new Vector2(1f, 1f);
MinimumScale = new Vector2(0.5f, 0.5f);
MaximumScale = new Vector2(20, 20);
CameraBox = new Polygon();
Mouse = m;
PreferredWidth = prefWidth;
PreferredHeight = prefHeight;
UpdateResize(windowWidth, windowHeight);
UpdateProjectionMatrix();
}
// Calculate the projection of a polygon on an axis and returns it as a [min, max] interval
public static void ProjectPolygon(Vector2 axis, Polygon polygon, ref float min, ref float max)
{
// To project a point on an axis use the dot product
float d = Vector2.Dot(axis, polygon.Points[0]);
min = d;
max = d;
foreach (Vector2 t in polygon.Points)
{
d = Vector2.Dot(t, axis);
if (d < min)
{
min = d;
}
else
{
if (d > max)
{
max = d;
}
}
}
}
// Structure that stores the results of the PolygonCollision function
// Check if polygon A is going to collide with polygon B for the given velocity
public static PolygonCollisionResult PolygonCollision(Polygon polygonA, Polygon polygonB, Vector2 velocity)
{
var result = new PolygonCollisionResult {Intersect = true, WillIntersect = true};
int edgeCountA = polygonA.Edges.Count;
int edgeCountB = polygonB.Edges.Count;
float minIntervalDistance = float.PositiveInfinity;
var translationAxis = new Vector2();
Vector2 edge;
// Loop through all the edges of both polygons
for (int edgeIndex = 0; edgeIndex < edgeCountA + edgeCountB; edgeIndex++)
{
edge = edgeIndex < edgeCountA ? polygonA.Edges[edgeIndex] : polygonB.Edges[edgeIndex - edgeCountA];
// ===== 1. Find if the polygons are currently intersecting =====
// Find the axis perpendicular to the current edge
var axis = new Vector2(-edge.Y, edge.X);
axis.Normalize();
// Find the projection of the polygon on the current axis
float minA = 0;
float minB = 0;
float maxA = 0;
float maxB = 0;
ProjectPolygon(axis, polygonA, ref minA, ref maxA);
ProjectPolygon(axis, polygonB, ref minB, ref maxB);
// Check if the polygon projections are currentlty intersecting
if (IntervalDistance(minA, maxA, minB, maxB) > 0) result.Intersect = false;
// ===== 2. Now find if the polygons *will* intersect =====
// Project the velocity on the current axis
float velocityProjection = Vector2.Dot(axis, velocity);
// Get the projection of polygon A during the movement
if (velocityProjection < 0)
{
minA += velocityProjection;
}
else
{
maxA += velocityProjection;
}
// Do the same test as above for the new projection
float intervalDistance = IntervalDistance(minA, maxA, minB, maxB);
if (intervalDistance > 0) result.WillIntersect = false;
// If the polygons are not intersecting and won't intersect, exit the loop
if (!result.Intersect && !result.WillIntersect) break;
// 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 vector
intervalDistance = System.Math.Abs(intervalDistance);
if (intervalDistance < minIntervalDistance)
{
minIntervalDistance = intervalDistance;
translationAxis = axis;
Vector2 d = polygonA.Center - polygonB.Center;
if (Vector2.Dot(d, translationAxis) < 0) translationAxis = -translationAxis;
}
}
// The minimum translation vector can be used to push the polygons appart.
// First moves the polygons by their velocity
// then move polygonA by MinimumTranslationVector.
if (result.WillIntersect) result.MinimumTranslationVector = translationAxis*minIntervalDistance;
result.IntervalDistance = minIntervalDistance;
return result;
}
public static PolygonCollisionResult PolygonCollision(Polygon polygonA, Polygon polygonB)
{
return PolygonCollision(polygonA, polygonB, Vector2.Zero);
}
public bool IsIntersecting(Polygon p)
{
PolygonCollisionResult polygonCollisionResult = PolygonCollision(this, p);
return polygonCollisionResult.Intersect;
}
private void ClampTranslations()
{
GenerateCameraBoundingBox();
var bbox = new Polygon(CameraBox);
bbox.Scale(TargetScale);
bbox.BuildEdges();
bbox.CalculateMaxMin();
if (bbox.Width > CameraBounds.Width && CameraBounds.Width >= CameraBounds.Height)
{
TargetScale.X = CameraBounds.Width/(PreferredWidth);
}
if (bbox.Height > CameraBounds.Height && CameraBounds.Height >= CameraBounds.Width)
{
TargetScale.Y = CameraBounds.Height/(PreferredHeight);
}
if (TargetScale.Y > TargetScale.X)
{
TargetScale.Y = TargetScale.X;
}
else if (TargetScale.X > TargetScale.Y)
{
TargetScale.X = TargetScale.Y;
}
CameraBox.Scale(Scale);
CameraBox.BuildEdges();
CameraBox.CalculateMaxMin();
//Clamp translation values
if (CameraBox.Max.X > CameraBounds.Max.X)
{
TargetWorldTranslation.X += ((CameraBox.Max.X) - CameraBounds.Max.X);
}
else if (CameraBox.Min.X < CameraBounds.Min.X)
{
TargetWorldTranslation.X += ((CameraBox.Min.X) - CameraBounds.Min.X);
}
//Clamp translation values
if (CameraBox.Max.Y > CameraBounds.Max.Y)
{
TargetWorldTranslation.Y += (CameraBox.Max.Y - CameraBounds.Max.Y);
}
else if (CameraBox.Min.Y < CameraBounds.Min.Y)
{
TargetWorldTranslation.Y += (CameraBox.Min.Y - CameraBounds.Min.Y);
}
}
