---------------------------------------------------------------------------- This text document is an extract from the help file included with the OBJto3DM application. ---------------------------------------------------------------------------- Introduction OBJto3DM converts a Wavefront object file (*.OBJ) to a Rhinoceros(R) model file (*.3DM). Installation To install this application, create a directory (the name and location do not matter), and extract the contents of the ZIP file into this directory. It is recommended that no other files be placed in the directory. If a previous version of this application is installed, it is recommended that either the previous version be uninstalled, or the new version be installed in a different directory. However, a previously created INI file may be kept; see INI file below. This application does not make any changes to the Windows registry, and does not create any files in other directories, except for files explicitly saved by the user. Uninstallation To uninstall this application, remove the directory containing the application. INI file Any changes to the settings in the Preferences dialog are saved in an INI file in the same directory as the application EXE file. The INI file should not be edited, but may be deleted to restore the default settings. If it is desired to retain the Preferences dialog settings from a previous version, the INI file from that version may be saved and copied into the directory in which this application is installed. ---------------------------------------------------------------------------- Usage notes The following OBJ file statements are currently supported: f - facet (polygon) g - group v - vertex usemtl - material vn - normal vector vt - texture map coordinate (UV coordinate) Groups and materials in the OBJ file are converted to polygon meshes in the 3DM file, as determined by the Use groups and Use materials check boxes in the Preferences dialog. If a statement in the OBJ file is not supported, or if it cannot be interpreted as valid, then it will either be ignored, or modified so that it is valid. In these cases, warning messages will be displayed, unless they are disabled in the Preferences dialog. The 3DM file format has some limitations in its support of polygon meshes: 1. In the OBJ file format, normal vectors and texture (UV) coordinates are associated with polygon corners. In a 3DM file, normal vectors and texture coordinates are associated with vertices. In order to use the normal vector and texture coordinate information in the OBJ file, it is possible that duplicate vertices may be added. 2. In the OBJ file format, a vertex may be shared by more than one material. If the materials are used to create separate mesh objects in the 3DM file, any shared vertices must be duplicated, since separate mesh objects in a 3DM file cannot share vertices. (The same situation arises if a vertex is shared by more than one group, but I haven't encountered any cases in which this actually causes a problem.) 3. The OBJ file format allows representation of mesh polygons with any number of sides. In a 3DM file, mesh polygons may only have three or four sides. OBJ to 3DM conversion requires changing mesh polygons with more than four sides to polygons with three or four sides (polygon triangulation). This application does not yet employ an algorithm to do this. As a temporary solution, polygons with more than four sides are (optionally) converted to NURBS polygons, which may have any number of sides. Within Rhino, if desired, the NURBS polygons can be manually converted to polygon meshes with the command MeshPolyline (Tools -> Polygon Mesh -> From Closed Polyline). This command does not appear to change the number of polygon vertices, but if that is important, as it would be in creating morph targets, the number of vertices should be manually verified. Rhino uses an 8-bit palette (256 colors) for layer colors. For this reason, a layer color modified within OBJto3DM may appear differently when viewed in Rhino. ---------------------------------------------------------------------------- Copyright information Copyright © 1999-2000 Dave Lerner All Rights Reserved This software is protected under United States and International Copyright Laws. Distribution by any means without express written consent of the author is forbidden. This software is provided As Is. The author accepts no liability or responsibility for damages in any form, regardless of cause. By using this software, you agree to the terms stated here and within the accompanying documentation. Rhinoceros (also known as Rhino) is a registered trademark of Robert McNeel & Associates.