3D Mesh

By Jos van Doorn July 19, 2004

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 pull-down 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 e-books 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.