BSP node (incomplete) on UnrealScript.

MyLevel.BSPNode.uc

//=============================================================================
// BSPNode.
//=============================================================================
class BSPNode expands Info;

struct TriPlane
{
    var Vector  points[3];
};


// BSP tree data
var BSPNode childNodes[2];
var BSPNode parentNode;
var BSPTree myTree;
var byte    numChildren;

// Geometrical data
var Plane   nodePlane;

var SubSector   frontSub, backSub; // only if numChildren == 0

enum EPointPlane
{
    PP_Front,
    PP_Inside,
    PP_Back
};


//===============================

// TriPlane normal
function Vector PlaneNormal(TriPlane plane, bool bBack)
{
    local Vector U, V;

    if ( bBack )
    {
        U = plane.points[1] - plane.points[0];
        V = plane.points[2] - plane.points[1];
    }

    else
    {
        U = plane.points[2] - plane.points[1];
        V = plane.points[1] - plane.points[0];
    }

    return U cross V;
}

// Center point of TriPlane's defining points
function Vector TriangleCenter(TriPlane plane)
{
    local Vector res;
    local int i;

    for ( i = 0; i < 3; i++ )
        res += plane.points[i];

    return res / 3;
}

// Front or back of TriPlane
function EPointPlane InFrontOf(TriPlane plane, Vector other)
{
    local float peq;

    peq = planeNormal(plane, false) dot (other - triangleCenter(plane));

    if ( peq > 0 )
        return PP_Front;

    else if ( peq == 0 )
        return PP_Inside;

    else
        return PP_Back;
}