// https://stackoverflow.com/a/18543221 for line-plane intersection.
/// <summary>
/// Returns true if the line segment intersects with the plane, or false otherwise.
///
/// Specify output parameters to receive more detailed information about the
/// intersection, such as the point at which it occurs and whether the line lies on
/// the plane.
/// </summary>
public static bool Intersect(LocalPlane plane, LocalSegment3 line)
{
Vector3 pointOnPlane_unused;
float amountAlongSegment_unused;
bool isLineCoplanar_unused;
return(Intersect(plane, line,
out pointOnPlane_unused,
out amountAlongSegment_unused,
out isLineCoplanar_unused));
}
/// <summary>
/// Returns true if the line segment intersects with the plane, or false otherwise.
///
/// If intersectInfiniteLine is specified, returns true if the line defined by the
/// line segment intersects with the plane, or false otherwise.
///
/// If this method returns true, no out parameters are set to NaN, and reasonable
/// defaults are chosen in edge-cases (such as a coplanar line). If this method
/// returns false, some or all output parameters may have no reasonable value and
/// are set to NaN.
///
/// pointOnPlane is the point along the line defined by the segment that intersects
/// with the plane. If the line segment is parallel to the plane and _on_ the plane,
/// pointOnPlane will be set to the center of the line segment as a convenience.
/// Otherwise, it will be set to a Vector3 containing all NaNs.
///
/// amountAlongSegment is the normalized amount from A to B along the line segment
/// that intersects with the plane. The line segment intersects with the plane only
/// if this value is between 0 and 1 (inclusive). If the line segment is parallel to
/// the plane and _on_ the plane, amountAlongSegment will be set to 0.5f. Otherwise,
/// amountAlongSegment will be set to NaN.
///
/// isLineCoplanar is true if the line defined by the line segment is wholly on
/// the plane, or false otherwise.
/// </summary>
public static bool Intersect(LocalPlane plane, LocalSegment3 line,
out Vector3 pointOnPlane,
out float amountAlongSegment,
out bool isLineCoplanar,
bool intersectInfiniteLine = false)
{
var planePosition = plane.position;
var planeNormal = plane.normal;
var a = line.a;
var b = line.b;
var u = b - a;
var uDotN = planeNormal.Dot(u);
if (uDotN.Abs() > float.Epsilon)
{
isLineCoplanar = false;
var w = a - planePosition;
amountAlongSegment = -(planeNormal.Dot(w)) / uDotN;
pointOnPlane = a + u * amountAlongSegment;
return(intersectInfiniteLine ||
(amountAlongSegment >= 0f && amountAlongSegment <= 1f));
}
else
{
var pa = a - planePosition;
if (planeNormal.Dot(pa).Abs() < float.Epsilon)
{
isLineCoplanar = true;
}
else
{
isLineCoplanar = false;
}
if (isLineCoplanar)
{
pointOnPlane = (a + b) / 2f;
amountAlongSegment = 0.5f;
return(true);
}
else
{
pointOnPlane = new Vector3(float.NaN, float.NaN, float.NaN);
amountAlongSegment = float.NaN;
return(false);
}
}
}