The graph it would be interesting. I'm positive I got the parameters voiced correctly now, this sniplet is cut & paste ready to go, if you have the dll I posted few messages ago. Attempting restore to describe traingles for this DLL's tri_tri_intersect().

[Nicholas Randall Forystek]

Public Type Vector3D
X As Single
Y As Single
Z As Single
End Type

Public Declare Function VertexPoint_Behind_TrianglePlane Lib
"maxlandlib.dll" Alias "PointBehindPoly" _
(ByVal VertexPointX As Single, ByVal VertexPointY As
Single, ByVal VertexPointZ As Single, _
ByVal TrianglePlaneNormalX As Single, ByVal
TrianglePlaneNormalY As Single, ByVal TrianglePlaneNormalZ As Single, _
ByVal TriangleSideLength1 As Single, ByVal
TriangleSideLength2 As Single, ByVal TriangleSideLength3 As Single) As
Boolean

Public Sub Main()

Dim v As Vector3D
Dim n As Vector3D
Dim p As Vector3D
Dim t1 As Vector3D
Dim t2 As Vector3D
Dim t3 As Vector3D

'make three points of a triangle
t1.X = 20: t1.Y = 0: t1.Z = 0
t2.X = 20: t2.Y = 20: t2.Z = 0
t3.X = -20: t3.Y = -20: t3.Z = 0

'get plane normal of a triangle
n = GetPlaneNormal(t1, t2, t3)

'get lengths of triangle sides
v.X = Distance(t3, t1)
v.Y = Distance(t1, t2)
v.Z = Distance(t2, t3)

'make up a point test scenario
p.X = 0: p.Y = 0: p.Z = -80
'check to see if the point is behind the illogical spun traingular
sphere in back spuns
Debug.Print VertexPoint_Behind_TrianglePlane(p.X, p.Y, p.Z, n.X, n.Y,
n.Z, v.X, v.Y, v.Z)

'make up a point test scenario
p.X = 0: p.Y = 0: p.Z = 60
'check to see if the point is behind the illogical spun traingular
sphere in back spuns
Debug.Print VertexPoint_Behind_TrianglePlane(p.X, p.Y, p.Z, n.X, n.Y,
n.Z, v.X, v.Y, v.Z)

'make up a point test scenario
p.X = 30: p.Y = 30: p.Z = 60
'check to see if the point is behind the illogical spun traingular
sphere in back spuns
Debug.Print VertexPoint_Behind_TrianglePlane(p.X, p.Y, p.Z, n.X, n.Y,
n.Z, v.X, v.Y, v.Z)

'make up a point test scenario
p.X = 30: p.Y = 30: p.Z = -60
'check to see if the point is behind the illogical spun traingular
sphere in back spuns
Debug.Print VertexPoint_Behind_TrianglePlane(p.X, p.Y, p.Z, n.X, n.Y,
n.Z, v.X, v.Y, v.Z)

End Sub

Public Function Distance(ByRef p1 As Vector3D, ByRef p2 As Vector3D) As
Single
Distance = Sqr(((p1.X - p2.X) * (p1.X - p2.X)) + ((p1.Y - p2.Y) *
(p1.Y - p2.Y)) + ((p1.Z - p2.Z) * (p1.Z - p2.Z)))
End Function

Public Function GetPlaneNormal(ByRef v0 As Vector3D, ByRef v1 As Vector3D,
ByRef v2 As Vector3D) As Vector3D
GetPlaneNormal = VectorNormalize(VectorCrossProduct(VectorSubtract(v0,
v1), VectorSubtract(v1, v2)))
End Function

Public Function VectorCrossProduct(ByRef v As Vector3D, ByRef u As Vector3D)
As Vector3D
VectorCrossProduct.X = ((v.Y * u.Z) - (v.Z * u.Y))
VectorCrossProduct.Y = ((v.Z * u.X) - (v.X * u.Z))
VectorCrossProduct.Z = ((v.X * u.Y) - (v.Y * u.X))
End Function

Public Function VectorSubtract(ByRef v As Vector3D, ByRef u As Vector3D) As
Vector3D
VectorSubtract.X = (v.X - u.X)
VectorSubtract.Y = (v.Y - u.Y)
VectorSubtract.Z = (v.Z - u.Z)
End Function

Public Function VectorNormalize(ByRef v As Vector3D) As Vector3D
Dim l As Single
l = Sqr(((v.X * v.X) + (v.Y * v.Y) + (v.Z * v.Z)))
If l = 0 Then l = 1
VectorNormalize.X = (v.X / l)
VectorNormalize.Y = (v.Y / l)
VectorNormalize.Z = (v.Z / l)
End Function