/// <summary>
/// Tests for intersection between a <see cref="Segment"/> and a <see cref="Plane"/>
/// </summary>
/// <param name="line">A <see cref="Segment"/> instance.</param>
/// <param name="plane">A <see cref="Plane"/> instance.</param>
/// <returns>An <see cref="IntersectionPair"/> instance containing the intersection information.</returns>
public static IntersectionPair Intersects(Segment segment, Plane plane)
{
if (TestIntersection(segment, plane) == false)
return new IntersectionPair(false, Vector3F.Zero);
Vector3F dir = segment.P1 - segment.P0;
float d = Vector3F.Dot(plane.Normal, dir);
float t = (plane.Constant - Vector3F.Dot(plane.Normal, segment.P0)) / d;
return new IntersectionPair(true, segment.P0 + dir*t);
}
/// <summary>
/// Tests for intersection between a <see cref="Segment"/> and a <see cref="Plane"/>.
/// </summary>
/// <param name="line">A <see cref="Segment"/> instance.</param>
/// <param name="plane">A <see cref="Plane"/> instance.</param>
/// <returns><see langword="true"/> if intersection occurs; otherwise, <see langword="false"/>.</returns>
public static bool TestIntersection(Segment segment, Plane plane)
{
// Get the position of the line's end point relative to the plane.
int sign0 = (int)plane.GetSign(segment.P0);
int sign1 = (int)plane.GetSign(segment.P1);
// Intersection occurs if the 2 endpoints are at oposite sides of the plane.
return ( ((sign0 > 0) && (sign1 < 0)) || ((sign0 < 0) && (sign0 > 0)) );
}
/// <summary>
/// Tests for intersection between a <see cref="Ray"/> and a <see cref="Plane"/>.
/// </summary>
/// <param name="ray">A <see cref="Ray"/> instance.</param>
/// <param name="plane">A <see cref="Plane"/> instance.</param>
/// <returns>An <see cref="IntersectionPair"/> instance containing the intersection information.</returns>
public static IntersectionPair Intersects(Ray ray, Plane plane)
{
bool intersect = false;
Vector3F hitPoint = Vector3F.Zero;
float denominator = Vector3F.Dot(plane.Normal, ray.Direction);
// Check if the ray is parrallel to the plane
if (MathFunctions.ApproxEquals(denominator, 0.0f))
{
// If the line is parallel to the plane it only intersects the plane if it is on the plane.
intersect = (plane.GetSign(ray.Origin) == MathFunctions.Sign.Zero);
if (intersect)
hitPoint = ray.Origin;
}
else
{
float t = (plane.Constant - Vector3F.Dot(plane.Normal, ray.Origin)) / denominator;
hitPoint = ray.Origin + ray.Direction * t;
intersect = true;
}
return new IntersectionPair(intersect, hitPoint);
}
/// <summary>
/// Initializes a new instance of the <see cref="Plane"/> class using given a plane to assign values from.
/// </summary>
/// <param name="p">A 3D plane to assign values from.</param>
public Plane(Plane p)
{
_normal = p.Normal;
_const = p.Constant;
}
/// <summary>
/// Builds a matrix that reflects the coordinate system about a plane.
/// </summary>
/// <param name="p">A <see cref="Plane"/> instance.</param>
/// <returns>A <see cref="Matrix4F"/> representing the reflection transformation.</returns>
/// <remarks>
/// This method normalizes the plane's equation before creating the reflection matrix.
/// </remarks>
public static Matrix4F Reflect(Plane p)
{
// TODO: Implement this.
throw new NotImplementedException();
}
/// <summary>
/// Builds a matrix that flattens geometry into a plane.
/// </summary>
/// <param name="lightPosition">A <see cref="Vector4F"/> instance representing the light source position.</param>
/// <param name="p">A <see cref="Plane"/> instance.</param>
/// <returns>A <see cref="Matrix4F"/> representing the shadow transformation.</returns>
/// <remarks>
/// This method flattens geometry into a plane, as if it were casting a shadow from a light.
/// </remarks>
public static Matrix4F Shadow(Vector4F lightPosition, Plane p)
{
// TODO: Implement this.
throw new NotImplementedException();
}
/// <summary>
/// Calculates the distance between a point and a plane.
/// </summary>
/// <param name="point">A <see cref="Vector3F"/> instance.</param>
/// <param name="plane">A <see cref="Plane"/> instance.</param>
/// <returns>The distance between a point and a plane.</returns>
/// <remarks>
/// <p>
/// A positive return value means teh point is on the positive side of the plane.
/// A negative return value means teh point is on the negative side of the plane.
/// A zero return value means the point is on the plane.
/// </p>
/// <p>
/// The absolute value of the return value is the true distance only when the plane normal is
/// a unit length vector.
/// </p>
/// </remarks>
public static float Distance(Vector3F point, Plane plane)
{
return Vector3F.Dot(plane.Normal, point) + plane.Constant;
}
