斜坡上的碰撞检查

public class BspNode
{
    public List<Vector3> Vertices { get; set; }

    // plane equation coefficients
    float A, B, C, D;

    BspNode front;
    BspNode back;

    public BspNode(Vector3 v1, Vector3 v2, Vector3 v3)
    {
        Vertices = new List<Vector3>();
        Vertices.AddRange(new[] { v1, v2, v3 });
        GeneratePlaneEquationCoefficients();
    }

    void GeneratePlaneEquationCoefficients()
    {

        // derive the plane equation coefficients A,B,C,D from the input vertex list.
    }

    bool IsInFront(Vector3 point)
    {
        bool pointIsInFront=true;
        // substitute point.x/y/z into the plane equation and compare the result to D
        // to determine if the point is in front of or behind the partition plane.
        if (pointIsInFront && front!=null)
        {
            // POINT is in front of this node\'s plane, so check it against the front list.
            pointIsInFront = front.IsInFront(point);
        }
        else if (!pointIsInFront && back != null)
        {
            // POINT is behind this plane, so check it against the back list.
            pointIsInFront = back.IsInFront(point);
        }
        /// either POINT is in front and there are no front children,
        /// or POINT is in back and there are no back children. 
        /// Either way, recursion terminates here.
        return pointIsInFront;            
    }

    /// <summary>
    /// determines if the line segment defined by v1 and v2 intersects any geometry in the tree.
    /// </summary>
    /// <param name=\"v1\">vertex that defines the start of the ray</param>
    /// <param name=\"v2\">vertex that defines the end of the ray</param>
    /// <returns>true if the ray collides with the mesh</returns>
    bool SplitsRay(Vector3 v1, Vector3 v2)
    {

        var v1IsInFront = IsInFront(v1);
        var v2IsInFront = IsInFront(v2);
        var result = v1IsInFront!=v2IsInFront;

        if (!result)
        {
            /// both vertices are on the same side of the plane,
            /// so this node doesn\'t split anything. Check it\'s children.
            if (v1IsInFront && front != null)
                result =  front.SplitsRay(v1, v2);
            else if (!v1IsInFront && back != null)
                result = back.SplitsRay(v1, v2);
        }
        else
        {
            /// this plane splits the ray, but the intersection point may not be within the face boundaries.
            /// 1. calculate the intersection of the plane and the ray : intersection
            /// 2. create two new line segments: v1->intersection and intersection->v2
            /// 3. Recursively check those two segments against the rest of the tree.
            var intersection = new Vector3();

            /// insert code to magically calculate the intersection here.

            var frontSegmentSplits = false;
            var backSegmentSplits = false;


            if (front!=null)
            {
                if (v1IsInFront) frontSegmentSplits=front.SplitsRay(v1,intersection);
                else if (v2IsInFront) frontSegmentSplits=front.SplitsRay(v2,intersection);
            }
            if (back!=null)
            {
                if (!v1IsInFront) backSegmentSplits=back.SplitsRay(v1,intersection);
                else if (!v2IsInFront) backSegmentSplits=back.SplitsRay(v2,intersection);
            }

            result = frontSegmentSplits || backSegmentSplits;
        }

        return result;
    }
} 

.SplitsRay()