Hi,

the polyhedron is defined by a list of 3D points, a list of edges, which refers to the point list (every edge is defined by 2 points references) and a face list which refers the edge list. All reference indices must start with 1.The coordinates of the points are defined in the world coordinate system.Every edge has a direction. The direction goes from the start point of the edge to the end point of the edge.Every face is defined by indices to the edge list. If a face is defined by three points (triangle face), then the face refers three edges. The faces must be defined clock wise.

This examples (see polyhedron.png) describes the topological definition of a cube.

The point list holds 8 points.

Points
P1 = (0,0,0)
p2 = (1000,0,0)
p3 = (1000,1000,0)
p4 = (0,1000,0)
p5 = (0,0,1000)
p6 = (1000,0,1000)
p7 = (1000,1000,1000)
p8 = (0,1000,1000)

The edge list holds 12 edges.

Edges Comments
e1 = (4,1) This edge goes from point 4 to point 1
e2 = (1,2) This edge goes from point 1 to point 2
e3 = (2,3) This edge goes from point 2 to point 3
e4 = (3,4) This edge goes from point 3 to point 4
e5 = (5,8 ) This edge goes from point 5 to point 8
e6 = (8,7) This edge goes from point 8 to point 7
e7 = (7,6) This edge goes from point 7 to point 6
e8 = (6,5) This edge goes from point 6 to point 5
e9 = (1,5) This edge goes from point 1 to point 5
e10 = (2,6) This edge goes from point 2 to point 6
e11 = (3,7) This edge goes from point 3 to point 7
e12 = (4,8 ) This edge goes from point 4 to point 8

The face list holds 6 faces.

Faces Comments
F1 = (1,2,3,4) This face defines the bottom face of the cube. It uses the edges e1, e2, e3, and e4.
F2 = (5,6,7,8 ) This face defines the top face of the cube. It uses the edges e5, e6, e7, and e8
F3 = (-1,12,-5,-9) This face defines the left face of the cube. It uses the edges –e1, e12, -e5, and –e9. Some edges are defined by negative indices. This depends of the traversing of the edges
F4 = (-2,9,- 8,-10) This face defines the front face of the cube. It uses the edges –e2, e9, -e8, and –e10.
F5 = (-3,10,-7,-11) This face defines the right face of the cube. It uses the edges –e3, e10, -e7, and –e11.
F6 = (-4,11,-6,-12) This face defines the back face of the cube. It uses the edges –e4, e11, -e6, and –e12.

To Display the Normals and Point and Edge-Numbers you can use the

Geometry_Tools

Regards.
Jörg

Hi Nemo, do you have smartparts script for cutplane like attachment? Thank you.

there is no function to define the CUTPLANE with two heights.
So you have to do some calculation for the cutting angle:

!calc cutting angle
cut_angle = ATAN ( ( h1 - h2 ) / REF_X ) 

!tranlsate and rotate the cutplane to the desired place
TRANSZ h1 
ROTZ 90 
CUTPLANE cut_angle 
RESTORE 2 

! the object to cut
BOX REF_X , REF_Y , REF_Z 

!remove cutting plane
CUTEND

Hi Nemo, can you send me script for change 2d rapresentation like attachment? (2d rapresentation with POLY2 if is possible) Thank you.

The next sketch on toilet-paper would be ignored

You need a proper sketchpad and a new pencil!