public static IEnumerable <Triangle3D> BoxTriangles(Vector3 a, Vector3 b)
{
float x = a.X;
float z = a.Y;
float y = a.Z;
float sx = b.X - a.X;
float sz = b.Y - a.Y;
float sy = b.Z - a.Z;
List <short> myelements = new List <short>();
List <Vector3> myvertices = new List <Vector3>();
//top
//if (drawtop)
{
short lastelement = (short)myvertices.Count;
myvertices.Add(new Vector3(x + 0.0f * sx, z + 1.0f * sz, y + 0.0f * sy));
myvertices.Add(new Vector3(x + 0.0f * sx, z + 1.0f * sz, y + 1.0f * sy));
myvertices.Add(new Vector3(x + 1.0f * sx, z + 1.0f * sz, y + 0.0f * sy));
myvertices.Add(new Vector3(x + 1.0f * sx, z + 1.0f * sz, y + 1.0f * sy));
myelements.Add((short)(lastelement + 0));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
myelements.Add((short)(lastelement + 3));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
}
//bottom - same as top, but z is 1 less.
//if (drawbottom)
{
short lastelement = (short)myvertices.Count;
myvertices.Add(new Vector3(x + 0.0f * sx, z + 0 * sz, y + 0.0f * sy));
myvertices.Add(new Vector3(x + 0.0f * sx, z + 0 * sz, y + 1.0f * sy));
myvertices.Add(new Vector3(x + 1.0f * sx, z + 0 * sz, y + 0.0f * sy));
myvertices.Add(new Vector3(x + 1.0f * sx, z + 0 * sz, y + 1.0f * sy));
myelements.Add((short)(lastelement + 0));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
myelements.Add((short)(lastelement + 3));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
}
//front
//if (drawfront)
{
short lastelement = (short)myvertices.Count;
myvertices.Add(new Vector3(x + 0 * sx, z + 0 * sz, y + 0 * sy));
myvertices.Add(new Vector3(x + 0 * sx, z + 0 * sz, y + 1 * sy));
myvertices.Add(new Vector3(x + 0 * sx, z + 1 * sz, y + 0 * sy));
myvertices.Add(new Vector3(x + 0 * sx, z + 1 * sz, y + 1 * sy));
myelements.Add((short)(lastelement + 0));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
myelements.Add((short)(lastelement + 3));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
}
//back - same as front, but x is 1 greater.
//if (drawback)
{
short lastelement = (short)myvertices.Count;
myvertices.Add(new Vector3(x + 1 * sx, z + 0 * sz, y + 0 * sy));
myvertices.Add(new Vector3(x + 1 * sx, z + 0 * sz, y + 1 * sy));
myvertices.Add(new Vector3(x + 1 * sx, z + 1 * sz, y + 0 * sy));
myvertices.Add(new Vector3(x + 1 * sx, z + 1 * sz, y + 1 * sy));
myelements.Add((short)(lastelement + 0));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
myelements.Add((short)(lastelement + 3));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
}
//if (drawleft)
{
short lastelement = (short)myvertices.Count;
myvertices.Add(new Vector3(x + 0 * sx, z + 0 * sz, y + 0 * sy));
myvertices.Add(new Vector3(x + 0 * sx, z + 1 * sz, y + 0 * sy));
myvertices.Add(new Vector3(x + 1 * sx, z + 0 * sz, y + 0 * sy));
myvertices.Add(new Vector3(x + 1 * sx, z + 1 * sz, y + 0 * sy));
myelements.Add((short)(lastelement + 0));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
myelements.Add((short)(lastelement + 3));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
}
//right - same as left, but y is 1 greater.
//if (drawright)
{
short lastelement = (short)myvertices.Count;
myvertices.Add(new Vector3(x + 0 * sx, z + 0 * sz, y + 1 * sy));
myvertices.Add(new Vector3(x + 0 * sx, z + 1 * sz, y + 1 * sy));
myvertices.Add(new Vector3(x + 1 * sx, z + 0 * sz, y + 1 * sy));
myvertices.Add(new Vector3(x + 1 * sx, z + 1 * sz, y + 1 * sy));
myelements.Add((short)(lastelement + 0));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
myelements.Add((short)(lastelement + 3));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
}
for (int i = 0; i < myelements.Count / 3; i++)
{
Triangle3D t = new Triangle3D();
t.PointA = myvertices[myelements[i * 3 + 0]];
t.PointB = myvertices[myelements[i * 3 + 1]];
t.PointC = myvertices[myelements[i * 3 + 2]];
yield return(t);
}
}
// intersect_RayTriangle(): intersect a ray with a 3D triangle
// Input: a ray R, and a triangle T
// Output: *I = intersection point (when it exists)
// Return: -1 = triangle is degenerate (a segment or point)
// 0 = disjoint (no intersect)
// 1 = intersect in unique point I1
// 2 = are in the same plane
public static int RayTriangle(Line3D R, Triangle3D T, out Vector3 I)
{
Vector3 u, v, n; // triangle vectors
Vector3 dir, w0, w; // ray vectors
float r, a, b; // params to calc ray-plane intersect
I = new Vector3();
// get triangle edge vectors and plane normal
u = T.PointB - T.PointA;
v = T.PointC - T.PointA;
//n = u.CrossProduct(v); // cross product
Vector3.Cross(ref u, ref v, out n);
//if (n == (Vector3D)0) // triangle is degenerate
// return -1; // do not deal with this case
dir = R.End - R.Start; // ray direction vector
w0 = R.Start - T.PointA;
a = -dot(n, w0);
b = dot(n, dir);
if (Math.Abs(b) < SMALL_NUM)
{ // ray is parallel to triangle plane
if (a == 0) // ray lies in triangle plane
return 2;
else return 0; // ray disjoint from plane
}
// get intersect point of ray with triangle plane
r = a / b;
if (r < 0.0) // ray goes away from triangle
return 0; // => no intersect
// for a segment, also test if (r > 1.0) => no intersect
I = R.Start + r * dir; // intersect point of ray and plane
// is I inside T?
float uu, uv, vv, wu, wv, D;
uu = dot(u, u);
uv = dot(u, v);
vv = dot(v, v);
w = I - T.PointA;
wu = dot(w, u);
wv = dot(w, v);
D = uv * uv - uu * vv;
// get and test parametric coords
float s, t;
s = (uv * wv - vv * wu) / D;
if (s < 0.0 || s > 1.0) // I is outside T
return 0;
t = (uv * wu - uu * wv) / D;
if (t < 0.0 || (s + t) > 1.0) // I is outside T
return 0;
return 1; // I is in T
}
RayTriangle(Line3D R, Triangle3D T, out Vector3 I)
{
Vector3 u, v, n; // triangle vectors
Vector3 dir, w0, w; // ray vectors
float r, a, b; // params to calc ray-plane intersect
I = new Vector3();
// get triangle edge vectors and plane normal
u = T.PointB - T.PointA;
v = T.PointC - T.PointA;
//n = u.CrossProduct(v); // cross product
Vector3.Cross(ref u, ref v, out n);
//if (n == (Vector3D)0) // triangle is degenerate
// return -1; // do not deal with this case
dir = R.End - R.Start; // ray direction vector
w0 = R.Start - T.PointA;
a = -dot(n, w0);
b = dot(n, dir);
if (Math.Abs(b) < SMALL_NUM)
{ // ray is parallel to triangle plane
if (a == 0) // ray lies in triangle plane
{
return(2);
}
else
{
return(0); // ray disjoint from plane
}
}
// get intersect point of ray with triangle plane
r = a / b;
if (r < 0.0) // ray goes away from triangle
{
return(0); // => no intersect
}
// for a segment, also test if (r > 1.0) => no intersect
I = R.Start + r * dir; // intersect point of ray and plane
// is I inside T?
float uu, uv, vv, wu, wv, D;
uu = dot(u, u);
uv = dot(u, v);
vv = dot(v, v);
w = I - T.PointA;
wu = dot(w, u);
wv = dot(w, v);
D = uv * uv - uu * vv;
// get and test parametric coords
float s, t;
s = (uv * wv - vv * wu) / D;
if (s < 0.0 || s > 1.0) // I is outside T
{
return(0);
}
t = (uv * wu - uu * wv) / D;
if (t < 0.0 || (s + t) > 1.0) // I is outside T
{
return(0);
}
return(1); // I is in T
}
static float SMALL_NUM = 0.00000001f; // anything that avoids division overflow
#endregion Fields
#region Methods
public static IEnumerable<Triangle3D> BoxTriangles(Vector3 a, Vector3 b)
{
float x = a.X;
float z = a.Y;
float y = a.Z;
float sx = b.X - a.X;
float sz = b.Y - a.Y;
float sy = b.Z - a.Z;
List<short> myelements = new List<short>();
List<Vector3> myvertices = new List<Vector3>();
//top
//if (drawtop)
{
short lastelement = (short)myvertices.Count;
myvertices.Add(new Vector3(x + 0.0f * sx, z + 1.0f * sz, y + 0.0f * sy));
myvertices.Add(new Vector3(x + 0.0f * sx, z + 1.0f * sz, y + 1.0f * sy));
myvertices.Add(new Vector3(x + 1.0f * sx, z + 1.0f * sz, y + 0.0f * sy));
myvertices.Add(new Vector3(x + 1.0f * sx, z + 1.0f * sz, y + 1.0f * sy));
myelements.Add((short)(lastelement + 0));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
myelements.Add((short)(lastelement + 3));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
}
//bottom - same as top, but z is 1 less.
//if (drawbottom)
{
short lastelement = (short)myvertices.Count;
myvertices.Add(new Vector3(x + 0.0f * sx, z + 0 * sz, y + 0.0f * sy));
myvertices.Add(new Vector3(x + 0.0f * sx, z + 0 * sz, y + 1.0f * sy));
myvertices.Add(new Vector3(x + 1.0f * sx, z + 0 * sz, y + 0.0f * sy));
myvertices.Add(new Vector3(x + 1.0f * sx, z + 0 * sz, y + 1.0f * sy));
myelements.Add((short)(lastelement + 0));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
myelements.Add((short)(lastelement + 3));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
}
//front
//if (drawfront)
{
short lastelement = (short)myvertices.Count;
myvertices.Add(new Vector3(x + 0 * sx, z + 0 * sz, y + 0 * sy));
myvertices.Add(new Vector3(x + 0 * sx, z + 0 * sz, y + 1 * sy));
myvertices.Add(new Vector3(x + 0 * sx, z + 1 * sz, y + 0 * sy));
myvertices.Add(new Vector3(x + 0 * sx, z + 1 * sz, y + 1 * sy));
myelements.Add((short)(lastelement + 0));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
myelements.Add((short)(lastelement + 3));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
}
//back - same as front, but x is 1 greater.
//if (drawback)
{
short lastelement = (short)myvertices.Count;
myvertices.Add(new Vector3(x + 1 * sx, z + 0 * sz, y + 0 * sy));
myvertices.Add(new Vector3(x + 1 * sx, z + 0 * sz, y + 1 * sy));
myvertices.Add(new Vector3(x + 1 * sx, z + 1 * sz, y + 0 * sy));
myvertices.Add(new Vector3(x + 1 * sx, z + 1 * sz, y + 1 * sy));
myelements.Add((short)(lastelement + 0));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
myelements.Add((short)(lastelement + 3));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
}
//if (drawleft)
{
short lastelement = (short)myvertices.Count;
myvertices.Add(new Vector3(x + 0 * sx, z + 0 * sz, y + 0 * sy));
myvertices.Add(new Vector3(x + 0 * sx, z + 1 * sz, y + 0 * sy));
myvertices.Add(new Vector3(x + 1 * sx, z + 0 * sz, y + 0 * sy));
myvertices.Add(new Vector3(x + 1 * sx, z + 1 * sz, y + 0 * sy));
myelements.Add((short)(lastelement + 0));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
myelements.Add((short)(lastelement + 3));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
}
//right - same as left, but y is 1 greater.
//if (drawright)
{
short lastelement = (short)myvertices.Count;
myvertices.Add(new Vector3(x + 0 * sx, z + 0 * sz, y + 1 * sy));
myvertices.Add(new Vector3(x + 0 * sx, z + 1 * sz, y + 1 * sy));
myvertices.Add(new Vector3(x + 1 * sx, z + 0 * sz, y + 1 * sy));
myvertices.Add(new Vector3(x + 1 * sx, z + 1 * sz, y + 1 * sy));
myelements.Add((short)(lastelement + 0));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
myelements.Add((short)(lastelement + 3));
myelements.Add((short)(lastelement + 1));
myelements.Add((short)(lastelement + 2));
}
for (int i = 0; i < myelements.Count / 3; i++)
{
Triangle3D t = new Triangle3D();
t.PointA = myvertices[myelements[i * 3 + 0]];
t.PointB = myvertices[myelements[i * 3 + 1]];
t.PointC = myvertices[myelements[i * 3 + 2]];
yield return t;
}
}