/// <summary>
/// Creates a new instance of a Ray.
/// </summary>
/// <param name="position">Starting position of the ray.</param>
/// <param name="direction">Unit direction vector that the ray is pointing.</param>
public Ray(Vector2 position, Vector2 direction, int collisionMask)
{
_position = position;
_direction = direction;
_collisionMask = collisionMask;
DebugTools.Assert(FloatMath.CloseTo(_direction.LengthSquared, 1));
}
private bool Contains(float x, float y)
{
var dx = Position.X - x;
var dy = Position.Y - y;
var d2 = dx * dx + dy * dy;
var r2 = Radius * Radius;
// Instead of d2 <= r2, use FloatMath.CloseTo to allow for some tolerance.
return((d2 < r2) || FloatMath.CloseTo(d2, r2));
}
private static bool EqualsApprox(Angle a, Angle b)
{
// reduce both angles
var aReduced = Reduce(a.Theta);
var bReduced = Reduce(b.Theta);
var aPositive = FlipPositive(aReduced);
var bPositive = FlipPositive(bReduced);
// The second two expressions cover an edge case where one number is barely non-negative while the other number is negative.
// In this case, the negative number will get FlipPositived to ~2pi and the comparison will give a false negative.
return(FloatMath.CloseTo(aPositive, bPositive) ||
FloatMath.CloseTo(aPositive + MathHelper.TwoPi, bPositive) ||
FloatMath.CloseTo(aPositive, bPositive + MathHelper.TwoPi));
}
public static float Clamp01(float value)
{
return(FloatMath.Clamp(value, 0, 1));
}
public bool IsEmpty()
{
return(FloatMath.CloseTo(Width, 0.0f) && FloatMath.CloseTo(Height, 0.0f));
}
public bool Intersects(Box2 box, out float distance, out Vector2 hitPos)
{
hitPos = Vector2.Zero;
distance = 0;
var tmin = 0.0f; // set to -FLT_MAX to get first hit on line
var tmax = float.MaxValue; // set to max distance ray can travel (for segment)
const float epsilon = 1.0E-07f;
// X axis slab
{
if (Math.Abs(_direction.X) < epsilon)
{
// ray is parallel to this slab, it will never hit unless ray is inside box
if (_position.X < FloatMath.Min(box.Left, box.Right) || _position.X > FloatMath.Max(box.Left, box.Right))
{
return(false);
}
}
// calculate intersection t value of ray with near and far plane of slab
var ood = 1.0f / _direction.X;
var t1 = (FloatMath.Min(box.Left, box.Right) - _position.X) * ood;
var t2 = (FloatMath.Max(box.Left, box.Right) - _position.X) * ood;
// Make t1 be the intersection with near plane, t2 with far plane
if (t1 > t2)
{
MathHelper.Swap(ref t1, ref t2);
}
// Compute the intersection of slab intersection intervals
tmin = FloatMath.Max(t1, tmin);
tmax = FloatMath.Min(t2, tmax); // Is this Min (SE) or Max(Textbook)
// Exit with no collision as soon as slab intersection becomes empty
if (tmin > tmax)
{
return(false);
}
}
// Y axis slab
{
if (Math.Abs(_direction.Y) < epsilon)
{
// ray is parallel to this slab, it will never hit unless ray is inside box
if (_position.Y < FloatMath.Min(box.Top, box.Bottom) || _position.Y > FloatMath.Max(box.Top, box.Bottom))
{
return(false);
}
}
// calculate intersection t value of ray with near and far plane of slab
var ood = 1.0f / _direction.Y;
var t1 = (FloatMath.Min(box.Top, box.Bottom) - _position.Y) * ood;
var t2 = (FloatMath.Max(box.Top, box.Bottom) - _position.Y) * ood;
// Make t1 be the intersection with near plane, t2 with far plane
if (t1 > t2)
{
MathHelper.Swap(ref t1, ref t2);
}
// Compute the intersection of slab intersection intervals
tmin = FloatMath.Max(t1, tmin);
tmax = FloatMath.Min(t2, tmax); // Is this Min (SE) or Max(Textbook)
// Exit with no collision as soon as slab intersection becomes empty
if (tmin > tmax)
{
return(false);
}
}
// Ray intersects all slabs. Return point and intersection t value
hitPos = _position + _direction * tmin;
distance = tmin;
return(true);
}