AutoCAD - CAVE Design Guidelines

AutoCAD Topics:

Advanced Modeling Extension, Release 2.1

Using the Solid Modeler, Advanced Modeling Extension, Release 2.1:

AutoCAD Release 12 has an optional Solid Modeler, the Advanced Modeling Extension, Release 2.1. This offers a wider range of solid modeling tools, and is useful for a wide range of applications. However, this Extended Modeler does not translate well when converting drawings to the CAVE.

We have found that ANY solid that REQUIRES the loading of the AME 2.1 to render a drawing, WILL NOT translate to the CAVE. We believe this is because of the way AutoCAD saves information. Solids that do not render without the AME 2.1 aren't actually saved as solids. But rather the information to generate the solids are, and the AME 2.1 Render processes and generates these solids and displays them. Without Rendering the solids with the AME 2.1, it simply looks like a few lines and has no real surfaces.

To make sure a drawing will function in the CAVE, Render the drawing WITHOUT loading AME 2.1, and use the basic AutoCAD Render. If the drawing appears correct, then it shouldn't have any problem in the CAVE. If you have a problem, there are a few ways to convert solids to make sure they function properly and will be discussed later, such as SOLMESH.

Please NOTE:
We used solely AutoCAD Release 12, and AME 2.1. These are our observations through this project. There may be several factors for why the AME 2.1 does not work, including:

Using Pre-defined SOLIDS:

There are pre-defined shapes built into the modeler, including domes, spheres, cones, cubes, etc. We have found that all of these solid objects will translate into the CAVE properly.

AutoCAD Release 12

Exporting Drawings to .DXF Format:

In order to get an AutoCAD Drawing (.DWG standard format) into the CAVE, you must have it in .DXF format. This is a simple process in AutoCAD. After loading your .DWG drawing, simply click on Files, then IMPORT/EXPORT, then DXF Out.... Input the amount of decimal precision you want, or simply hit (return) if you do not know. This will save your current drawing as a .DXF file that you can use the conversion utilities mentioned on.

The current viewpoint and whether its rendered or not, do not affect the .DXF file. You do not have to render it and save it, nor do you have to move the viewpoint around to a specific view. Both are irrelevant when saving to .DXF format.

However, the coordinate system of the drawing is important. The coordinate system used in the orientation of the drawing will be translated to the CAVE. This is discussed later, in Aligning AutoCAD Drawings in the CAVE.

Using AutoCAD Layers:

One of the most useful tools in AutoCAD development is the use of Layers. By defining layers, you can turn objects on and off and change the properties of all objects of a given layer. This can be applied to converting files to CAVE format as well.

When saving your .DXF file, it acknowledges any layers that you may have. So, any layers you have turned off when saving your .DXF file, will not show up in the CAVE. And vice versa, all layers turned on when the .DXF file is saved will be shown in the CAVE.

Ideally, you would want to be able to bring a drawing into the CAVE and turn layers on and off at will. This would allow you the greatest freedom of design and visualization. However, at this time, the CAVE cannot do this. You can navigate through your drawing, but you cannot turn layers on and off. From what I understand, there is work being developed towards this, but it is not available at present.

Please NOTE:
You have to create a different .DXF file for every variation of layers you want to see in the CAVE.

Scaling and Size:

The scale and size of an AutoCAD drawing is not important to its conversion to the CAVE. The conversion utilities allow for scaling of the drawings to fit in the CAVE. You do not have to worry about scaling your drawings in AutoCAD before saving them to .DXF format.

Incorporating Multiple AutoCAD Files


The X-refenece ATTACH function is used in AutoCAD to reference a .DWG file in another .DWG file. This is a link, and not a copy function. Although, you can see the linked file in your drawing, it is just a link and does not really exist in the drawing. When the drawing is loaded, the linked file is also loaded and displayed. This is generally used when multiple people are working on drawings, and one makes a modification to the linked file, the other person sees the changes because it reloads the linked file.

Because of this 'link', X-referenced files do NOT translate to the CAVE. When saving the .DXF file, none of the referenced files are saved. Meaning, any X-referenced files in a given drawing will not show up in the CAVE.

Correctly Inserting Solids, via AutoLISP:

To solve this problem, you must actually copy or insert the drawing. This can be achieved by using an AutoLISP application that is standard with Release 12.

Function: INSRTSOL

Click on FILES, then Applications, then File.... Select the AutoLISP file, WBLKSOL.LSP located in the \ACAD\SAMPLES\ directory. Click LOAD. This will load the AutoLISP file.

From the AutoCAD command line, type INSRTSOL and specify the name of the file you wish to insert into your current drawing. Follow the options, and you're done.

This copies the drawing you specified into your current drawing, permanently. You can modify as you wish and move it around as you need to. After you have used INSRTSOL, you can save to .DXF format and it will appear successfully in the CAVE.

Aligning AutoCAD Drawings in the CAVE

When converting from AutoCAD to the CAVE, the CAVE uses the same coordinates that were used in the AutoCAD drawing. However, it uses the coordinates from AutoCAD in the CAVE coordinate system.

Think of the CAVE as a square room. The origin of the coordinate system, point (0,0,0), is positioned in the center of the floor of the room. The plane of the floor is the X-Y plane, and the Z-axis travels up towards the ceiling.

The coordinates from your AutoCAD drawing are translated into this coordinate system. So, the origin in AutoCAD is the same origin in the CAVE. You can move your entire drawing as a block to the position you would like in AutoCAD, if you find it does not translate effectively to the CAVE.

You may also find that the X-Y plane orientation of your drawing varies from the CAVE. You can use the conversion utilities' rotation ability to correct for this.

Please NOTE:
Coordinate modifications must be made in AutoCAD prior to saving the .DXF file. The conversion utilities allow you to rotate your drawing around all three axes, but you cannot move your drawing.

Using AutoCAD colors

AutoCAD Release 12 has 256 colors built-in, basically because it's an old DOS-Based VGA program. You can define objects using the 256 color-scheme in AutoCAD and it will translate to the same color-scheme in the CAVE. This can be useful to show different aspects of your drawing, by differing components or layers by color.

We have not used AutoCAD Release 13, and do not know if its color-scheme translates into the CAVE.

General Recommendations


We found the SOLMESH function to be the most useful function to make solids CAVE-Ready. The SOLMESH function makes a surface mesh of the solid, generating all the surfaces of a solid. The standard AutoCAD Render can then process these surfaces and generate the proper drawing without using AME 2.1. This means the solid can now be brought into the CAVE properly.

You can highlight single solid objects, or an entire group of objects at once, and SOLMESH them. For complicated objects you may have to adjust the default variables (which define the number of mesh surfaces to use when using SOLMESH), but we did not find this to a problem at all with SOLMESH.

If an object renders only using AME 2.1, and not under the standard AutoCAD Render (or CAVE), then just SOLMESH it. It's the easiest method, and you can highlight your entire drawing at once. This does greatly increase the file size however, since it is creating thousands of surfaces for your objects. For very large drawings, you may require a fairly powerful computer and drive space. Our basic final design, has rougly 4000 or so surfaces and is approximately 1.8 megabytes in .DXF format.


Use colors as much as possible in your AutoCAD drawing. The shading and colors in the CAVE look rather nice. Color-code your drawing in a fashion that makes explaining your design the easiest, either by component or relative use or material.

Besides, a color 3D representation simply looks more impressive than a detailed design all in grey.


If you start converting more than a few .DXF files into CAVE (.PFB) format, you'll realize that using the DXFconvert script is essential. It saves enormous amounts of time, especially if you are trying different scales, rotation angles, etc. You can run the script in a matter of seconds. Load up the CAVE Simulator, see its orientation, and note needed changes. You can repeat this process very quickly, which is very helpful. You want to spend your time in the CAVE, not messing around with files.

Enjoy the DXFconvert script, it's great.

Written By:Heath Beres

Page Last Updated: 4/30/98