/// <summary>
/// split polygon by plane and push the results to polygon lists
/// </summary>
/// <param name="polygon">polygon to split</param>
/// <param name="coplanarFront">list of coplanar polygons in front plane</param>
/// <param name="coplanarBack">list of coplanar polygons in back plane</param>
/// <param name="front">list of polygons in front plane</param>
/// <param name="back">list of polygons in back plane</param>
public void Split(CSGPolygon polygon, List<CSGPolygon> coplanarFront, List<CSGPolygon> coplanarBack, List<CSGPolygon> front, List<CSGPolygon> back)
{
var verticesCount = polygon.Vertices.Count;
var classes = new Plane.PointClass[verticesCount];
var polygonClass = Plane.PointClass.Coplanar;
for (int i = 0; i < verticesCount; i++)
{
var t = Vector3.Dot(Normal, polygon.Vertices[i].P) - Distance;
var type = (t < -epsylon
? Plane.PointClass.Back
: (t > epsylon ? Plane.PointClass.Front : Plane.PointClass.Coplanar));
//classes[i] = ClassifyPoint(polygon.Vertices[i].P);
polygonClass |= type; //classes[i];
classes[i] = type;
}
switch (polygonClass)
{
case Plane.PointClass.Coplanar:
{
if (Vector3.Dot(Normal, polygon.Plane.Normal) > 0)
{
coplanarFront.Add(polygon);
}
else
{
coplanarBack.Add(polygon);
}
}
break;
case Plane.PointClass.Front:
{
front.Add(polygon);
}
break;
case Plane.PointClass.Back:
{
back.Add(polygon);
}
break;
case Plane.PointClass.Intersection:
{
var frontList = new List<CSGVertex>(4);
var backList = new List<CSGVertex>(4);
for (int i = 0; i < verticesCount; i++)
{
var j = (i + 1) % verticesCount;
var class0 = classes[i];
var class1 = classes[j];
var v0 = polygon.Vertices[i];
var v1 = polygon.Vertices[j];
if (class0 != Plane.PointClass.Back)
{
frontList.Add(v0);
}
if (class0 != Plane.PointClass.Front)
{
backList.Add(class0 != Plane.PointClass.Back ? new CSGVertex(v0) : v0);
}
if ((class0 | class1) == Plane.PointClass.Intersection)
{
var q = new CSGVertex(polygon.Vertices[0]);
// find intersection point
//IntersectSegment(v0.P, v1.P, out t, out q.P);
var t = (this.Distance - Vector3.Dot(this.Normal, v0.P)) / Vector3.Dot(this.Normal, v1.P - v0.P);
// interpolate
q.P = Vector3.Lerp(v0.P, v1.P, t);
q.N = Vector3.Lerp(v0.N, v1.N, t);
q.UV = Vector2.Lerp(v0.UV, v1.UV, t);
frontList.Add(q);
backList.Add(new CSGVertex(q));
}
}
if (frontList.Count >= 3)
{
front.Add(new CSGPolygon(polygon.Id, frontList));
}
if (backList.Count >= 3)
{
back.Add(new CSGPolygon(polygon.Id, backList));
}
}
break;
}
}
/// <summary>
/// split polygon by plane and push the results to polygon lists
/// </summary>
/// <param name="polygon">polygon to split</param>
/// <param name="coplanarFront">list of coplanar polygons in front plane</param>
/// <param name="coplanarBack">list of coplanar polygons in back plane</param>
/// <param name="front">list of polygons in front plane</param>
/// <param name="back">list of polygons in back plane</param>
public void Split(CSGPolygon polygon, List <CSGPolygon> coplanarFront, List <CSGPolygon> coplanarBack, List <CSGPolygon> front, List <CSGPolygon> back)
{
var verticesCount = polygon.Vertices.Count;
var classes = new Plane.PointClass[verticesCount];
var polygonClass = Plane.PointClass.Coplanar;
for (int i = 0; i < verticesCount; i++)
{
var t = Vector3.Dot(Normal, polygon.Vertices[i].P) - Distance;
var type = (t < -epsylon
? Plane.PointClass.Back
: (t > epsylon ? Plane.PointClass.Front : Plane.PointClass.Coplanar));
//classes[i] = ClassifyPoint(polygon.Vertices[i].P);
polygonClass |= type; //classes[i];
classes[i] = type;
}
switch (polygonClass)
{
case Plane.PointClass.Coplanar:
{
if (Vector3.Dot(Normal, polygon.Plane.Normal) > 0)
{
coplanarFront.Add(polygon);
}
else
{
coplanarBack.Add(polygon);
}
}
break;
case Plane.PointClass.Front:
{
front.Add(polygon);
}
break;
case Plane.PointClass.Back:
{
back.Add(polygon);
}
break;
case Plane.PointClass.Intersection:
{
var frontList = new List <CSGVertex>(4);
var backList = new List <CSGVertex>(4);
for (int i = 0; i < verticesCount; i++)
{
var j = (i + 1) % verticesCount;
var class0 = classes[i];
var class1 = classes[j];
var v0 = polygon.Vertices[i];
var v1 = polygon.Vertices[j];
if (class0 != Plane.PointClass.Back)
{
frontList.Add(v0);
}
if (class0 != Plane.PointClass.Front)
{
backList.Add(class0 != Plane.PointClass.Back ? new CSGVertex(v0) : v0);
}
if ((class0 | class1) == Plane.PointClass.Intersection)
{
var q = new CSGVertex(polygon.Vertices[0]);
// find intersection point
//IntersectSegment(v0.P, v1.P, out t, out q.P);
var t = (this.Distance - Vector3.Dot(this.Normal, v0.P)) / Vector3.Dot(this.Normal, v1.P - v0.P);
// interpolate
q.P = Vector3.Lerp(v0.P, v1.P, t);
q.N = Vector3.Lerp(v0.N, v1.N, t);
q.UV = Vector2.Lerp(v0.UV, v1.UV, t);
frontList.Add(q);
backList.Add(new CSGVertex(q));
}
}
if (frontList.Count >= 3)
{
front.Add(new CSGPolygon(polygon.Id, frontList));
}
if (backList.Count >= 3)
{
back.Add(new CSGPolygon(polygon.Id, backList));
}
}
break;
}
}
