3D Mesh
In this tutorial, we'll explore the world of 3D mesh. A
mesh in AutoCAD is a rectangle or connected rectangles with
points very much the same as the grid points. Here's my 3D mesh.
This is what I entered at the prompt: Command: 3dmesh
Mesh M size: 4
Mesh N size: 3
Vertex (0, 0): 0,0
Vertex (0, 1): 0,1
Vertex (0, 2): 0,2
Vertex (1, 0): 1,0
Vertex (1, 1): 1,1
Vertex (1, 2): 1,2
Vertex (2, 0): 2,0
Vertex (2, 1): 2,1
Vertex (2, 2): 2,2
Vertex (3, 0): 3,0
Vertex (3, 1): 3,1
Vertex (3, 2): 3,2 The M size stands for the number of
vertical lines. That's what I did in the example. I gave an M
size of four. So there are four vertical lines. For the N size
I entered three. The example mesh has got three horizontal
lines. The horizontal and vertical lines form rectangles.
After entering the numbers for the M size and the N size there
is asked for values of the vertices. There is asked for vertex
(0,0). Vertex (0,0) the first point of the 3D mesh. That point
is in the lower left corner. I entered two numbers separated by
a comma. We go to the next vertex. We go to vertex (0,1). That
vertex is above the first vertex. I entered 0,1. And I went on
with giving values to the vertices. After entering a value for
the last vertex the 3D mesh is created. The 3D mesh consists out
of six rectangles. But the 3D mesh is one entity. We can
measure the distances between the horizontal and vertical lines.
The distance is always one. That's so because of the numbers I
entered for the vertices.
Here is another 3D mesh I created. This 3D mesh has got
unequal sizes. It has got unequal sizes because of the way I
entered values for the vertices. This is what I typed at the
command prompt: Command: 3DMESH
Mesh M size: 4
Mesh N size: 3
Vertex (0, 0): 0,0
Vertex (0, 1): 0,3
Vertex (0, 2): 0,8
Vertex (1, 0): 1,0
Vertex (1, 1): 1,3
Vertex (1, 2): 1,8
Vertex (2, 0): 5,0
Vertex (2, 1): 5,3
Vertex (2, 2): 5,8
Vertex (3, 0): 7,0
Vertex (3, 1): 7,3
Vertex (3, 2): 7,9 Create the same 3D mesh. Just follow the
example. And then check the distances. You will see that the
distances are unequal. That's what I did up till now. I only
entered two numbers as there was asked for a value for the
vertices. The first number is for the M size. The second
number is for the N size. But I also could have entered a third
number. The third number stands for a height. You can give
each vertex point of the 3D mesh a height. This is the 3D mesh I
created. This is what I entered at the command prompt:
Command: 3dmesh
Mesh M size: 4
Mesh N size: 3
Vertex (0, 0): 0,0,0
Vertex (0, 1): 0,3,0
Vertex (0, 2): 0,8,0
Vertex (1, 0): 1,0,0
Vertex (1, 1): 1,3,1
Vertex (1, 2): 1,8,0
Vertex (2, 0): 5,0,0
Vertex (2, 1): 5,3,1
Vertex (2, 2): 5,8,0
Vertex (3, 0): 7,0,0
Vertex (3, 1): 7,3,0
Vertex (3, 2): 7,8,0 There are a couple of more things that
must be said. For the M size and the N size a number can be
entered. That number can be between 2 and 256.
Once you have a 3D mesh you can use the Hide command to have
hidden lines removed from the display. You can also render a 3D
mesh.
You can even save a 3D mesh as a picture. Click on File on
the menu bar and on Export on the pulldown menu. Different file
types can be selected. You can create a solid using the box
command or other commands. You can also do something with the
extrude command. But with a 3D mesh you have a different
model. You cannot use the Union command on solids and a 3D mesh.
That doesn't work. You have created a 3D mesh. And now you
want to change the height that was given to a vertex. You can.
Use the stretch command. Select the vertex and enter a
displacement or drag the vertex to a new height. Maybe you start
with a 3D mesh without height. For the values of the vertices
you entered just two numbers. Next you use the stretch command
to change the height.
We have now seen how the 3D mesh command works. It isn't
really too complicated. Just keep the distances between the
lines the same. If you do it will be easier to work with a 3D
mesh. You can easily located each vertex point of the 3D mesh.
And give it a proper height. About the Author
Jos van Doorn is an AutoCAD specialist and AutoLISP
programmer.
He has published a series of
ebooks on AutoCAD and AutoLISP topics, which are available for
downloading at his
website.
He is also publisher of the free ACAD Newsletter. To subscribe,
visit the newsletter's
webpage.
