public override bool IsCollision(CollisionMask aOther)
{
if (aOther is Circle)
{
var lCircle = (Circle)aOther;
}
if (aOther is Ray)
{
var lRay = aOther as Ray;
//positions
var x1 = this.Position.X;
var y1 = this.Position.Y;
var x2 = lRay.Position.X;
var y2 = lRay.Position.Y;
//direction vectors (unit length)
var u1x = Math.Cos(mActualAngle * Math.PI / 180);
var u1y = Math.Sin(mActualAngle * Math.PI / 180);
var u2x = Math.Cos(lRay.mActualAngle * Math.PI / 180);
var u2y = Math.Sin(lRay.mActualAngle * Math.PI / 180);
//parallel lines
if (u1x * u2y - u1y * u2x == 0.0)
{
//false for simplicity, not considering one ray covering the other one
return(false);
}
//parameter of the crossing point for ray 1 ("this" ray)
var t1 = ((y1 - y2) * u2x - (x1 - x2) * u2y) / (u1x * u2y - u1y * u2x);
if (t1 <= 0)
{
//crossing point is behind the origin of ray 1
return(false);
}
var t2 = 0.0;
//there are two ways to calculate the second parameter,
//at least one should be always possible
if (u2x != 0)
{
t2 = (x1 - x2 + t1 * u1x) / u2x;
}
else if (u2y != 0)
{
t2 = (y1 - y2 + t1 * u1y) / u2y;
}
else
{
return(false);
}
if (t1 > 0 && t2 > 0 && t1 < this.mLength && t2 < lRay.mLength)
{
return(true);
}
else
{
return(false);
}
}
if (aOther is Circle)
{
var lCircle = aOther as Circle;
//base point of the ray
var x0 = this.Position.X;
var y0 = this.Position.Y;
//direction vector of the ray, unit length
var ux = Math.Cos(mActualAngle * Math.PI / 180);
var uy = Math.Sin(mActualAngle * Math.PI / 180);
//circle position
var m = lCircle.Position.X;
var n = lCircle.Position.Y;
//circle radius
var r = lCircle.Radius;
var dx = x0 - m;
var dy = y0 - n;
//solving for t: (ux^2 + uy^2) * t^2 + 2 * (dx*ux + dy*uy) * t + dx^2 + dy^2 - r^2 = 0
var a = 1; //ux^2 + uy^2 = 1, direction vector has unit length
var b = 2 * (dx * ux + dy * uy);
var c = dx * dx + dy * dy - r * r;
var D = b * b - 4 * a * c;
var t1 = 0.0;
var t2 = 0.0;
if (D <= 0)
{
return(false);
}
else
{
t1 = (-b - Math.Sqrt(D)) / (2 * a);
t2 = (-b + Math.Sqrt(D)) / (2 * a);
if (t1 > 0 && t1 < mLength)
{
return(true);
}
if (t2 > 0 && t2 < mLength)
{
return(true);
}
return(false);
}
}
return(false);
}
public abstract bool IsCollision(CollisionMask aOther);
