The 3D Studio Converter adds three entries to conversion lists:

3D Studio .3DS object
3D Studio .ASC object
3D Studio .MLI materials

This Converter reads and writes 3D Studio objects in the ".3DS" object format and ".MLI" material library format. It also reads and writes objects in the 3D Studio ".ASC" ASCII text file format.

3D Studio files are largely compatible between releases, so this Converter can read and write files for any version of 3D Studio for DOS.

Geometry
The 3D Studio ".3DS" object format stores objects composed entirely of triangles. Object names are limited to eight characters. Objects can be linked in parent-child hierarchies.

3D Studio polygons can be sensitive to orientation, meaning each triangle is only visible from one side. This is the correct orientation for programs such as LightWave and Wavefront. If two-sided materials are used, the 3D Studio polygons might be randomly oriented.

Material attributes
3D Studio has rich material attributes that closely resemble those used by Interchange. 3D Studio stores its material descriptions within an object or within a material library. Most attributes are translated by Interchange, such as the material name, diffuse color, specular color, and transparency. Material names are limited to fifteen characters. 3D Studio "shininess" becomes the specular coefficient. On reading, the ambient color is ignored, but when creating 3D Studio materials, the ambient color is set to white light.

Both Gouraud and Phong shading in 3D Studio are translated as Interchange's "smooth" material setting. When creating 3D Studio materials, "smooth" is always written as Phong shading. 3D Studio's "self-illuminated" attribute is translated as Interchange's "luminous" setting. The wireframe attribute is preserved.

3D Studio materials can have a "two-sided" attribute, which makes those polygons visible from both sides, regardless of the orientation of the normal. This setting will be preserved as best as possible from other formats.

If present, texture map references become part of the material. Only the first (or diffuse) map is preserved.

Reading 3DS files
You can save ".3DS" format objects from the "File / Save" and "File / Save Selected" menu items within the 3D Editor of 3D Studio.

When translating 3D Studio objects to other formats, the resulting object looks like the object you had in the 3D Editor and in frame 1 of the Keyframer. Positions from other frames are not translated.

Writing 3D Studio files
When translating hierarchical objects to 3D Studio format, each object becomes a separate named object in the 3D Studio 3D Editor. Objects with no polygons become dummy objects with different-sized bounding boxes approximately 20 units in size. In the Keyframer, objects are linked with proper parent-child relationships. Centers of rotation are preserved.

Once an object is loaded into the 3D Editor, you may need to perform the "Surface / Normals / Object Unify" command. This operation is necessary when converting objects from formats that do not require polygons to have a correct orientation.

For example, most LightWave objects have polygons with proper orientation, but most DXF objects have polygons with random orientation. If the automatic "object unify" command doesn't work perfectly, you can manually flip polygon normals with the "Surface / Normals / Face Flip" command. Or, give all the materials used in the object the "two-sided" attribute in the Materials Editor. Or, use the "Force 2-sided" option in the 3D Studio renderer. For more information about polygon orientation, see the "3D Concepts" chapter in the Interchange manual.

Up to 32 smoothing groups are possible in a 3D Studio object. Smoothing groups will be created for polygons that share the same surface that has smoothing set. Alternatively, you can re-create smoothing groups using the 3D Editor's "Surface / Smoothing / Object / Auto Smooth" command. This method results in smoothing groups that are the most compatible with 3D Studio. Any other program's smoothing techniques might not be the same as 3D Studio's.

Each edge of a 3D Studio triangle can be set as visible or invisible. The "Use original edges" option controls whether Interchange will make all triangle edges visible, or whether the edges of the original object will be shown. Edge visibility only affects how the object appears in the 3D Editor and Keyframer, it does not affect the final rendering. For more information, see the Options dialog description below.

This Converter can read and write the 3D Studio ".ASC" files. These files are editable in any text editor. "ASC" files only store a partial representation of the information in a 3D Studio ".3DS" file. For example, they only contain the name of a material, not the material's attributes. For the best fidelity in translations, use the ".3DS" format. "ASC" files are used by several public-domain utilities.

Material Libraries
To load a material library into 3D Studio's Materials Editor, use the "Library / Load Library" or "Library / Merge Library" menu items. ".MLI" is the expected filename extension.

You can also use material libraries in AutoCAD Release 13 using the MATLIB command. However, it only uses the color, ambient, reflection and roughness attributes of each surface.

Material libraries can be converted to Interchange Surface files, or vice-versa. For more information about Surface files, see the "Surface Converter" chapter in the Interchange manual.

Options dialog

Import section
When Merge to quads is set, Interchange will use the edge visibility flags in the object to merge adjacent triangles into four-sided polygons. No other merging is performed.

Export section
Ignore centers creates a 3D Studio file with all centers set to the origin. This can side-step object placement problems in other programs that claim to import 3D Studio files.

Use original edges will create a 3D Studio object with the edge visibility set to match the polygons of the original object. This can be used to make many-sided polygons from formats such as Wavefront and LightWave look correct within the 3D Studio editor even though the polygons have been reduced to triangles.

When Colored wireframes is set, the model's objects will be assigned distinct wireframe colors when viewed in 3D Studio's 3D Editor. Up to 64 separate colors are available.

When Limit number of materials is set, Interchange will attempt to reduce the number of materials to the given number. By default, the limit is enforced at 128. 3D Studio Release 4 and earlier have a limit of 255 materials per scene. When converting objects to 3D Studio from other file formats, it is easy to exceed this limit. Interchange handles this in several ways, such as folding together any polygons that only differ in name, choosing the most commonly represented polygons, merging similar materials, etc.

Make UVs controls whether per-point UV values will be exported.

By setting the Texture bitmap extension, you can force all texture bitmap references to a particular file type. Interchange only translates the texture filename, not the bitmap data itself. If this is not set, then texture bitmap filenames are not altered.

3D Studio Max
3D Studio Max does not have a file format per-se that could be supported by Interchange. Its file format is a collection of persistent data stored by each of the dozens of plug-ins that make up Max. Not only would Autodesk need to document all this unrelated data, but each third-party plug-in maker would need to document their data, as well as document how to regenerate procedural geometry from the minimal information stored in the file format.

Instead, Viewpoint plans to create a plug-in for 3D Studio Max that connects all of Interchange's translation abilities to Max. When this plug-in becomes available, it will be part of Interchange. Visit the Viewpoint Web site at www.viewpoint.com for the latest information.

Background
3D Studio is made by Kinetix, a division of Autodesk:

Kinetix
642 Harrison St.
San Francisco, CA 94107
(415) 547-2000
(415) 547-2222 FAX
www.ktx.com