STLB Files
Stereolithography (binary)

These are some examples of STLB, or "binary STL" files. "STL" stands for "stereolithography", and indicates that the primary purpose of this file format is to describe the shape of a 3D stationary object. Stereolithography is a means of creating physical 3D models of such objects, using resin or carefully cut and joined pieces of paper.

The STLB file usually has a filename extension of ".stlb". It contains a description of the surface of a solid that has been decomposed into triangles. The vertices of the triangles should be listed in counterclockwise order, as viewed from outside the surface. A normal vector for the triangle may also be listed.

The file begins with a solid record, (which can include a name for the object), and ends with an endsolid record. Each triangle begins with a facet record and ends with an endfacet record. The normal vector, if given, is included as part of the facet record, and is identified by the normal keyword. The normal vector should have unit length. The three vertices of the triangle are delimited by outer loop and endloop records. Each vertex is described on a vertex record that lists its (X,Y,Z) coordinates.

A binary STL file has the following structure:

• An 80 byte ASCII header that can be used as a title.
• A 4 byte unsigned long integer, the number of facets.
• For each facet, a facet record of 50 bytes.

The facet record has the form:

• The normal vector, 3 floating values of 4 bytes each;
• Vertex 1 XYZ coordinates, 3 floating values of 4 bytes each;
• Vertex 2 XYZ coordinates, 3 floating values of 4 bytes each;
• Vertex 3 XYZ coordinates, 3 floating values of 4 bytes each;
• An unsigned integer, of 2 bytes, that should be zero;

STLB File Characteristics:

• binary
• No color information
• 3D
• No compression
• 1 image

Related Data and Programs:

For debugging, or small examples, it is an ASCII stereolithography file format is available. For information, see the STLA format.

Reference:

1. 3D Systems, Inc,
   Stereolithography Interface Specification,
   October 1989.

Programs to convert an STLB file to another format:

• The C++ program IVCON can read in an STLB file and write it out in a variety of 3D formats.
• The FORTRAN90 program IVREAD can read in an STLB file and write it out in a variety of 3D formats.
• The Visual Toolkit routine vtkSTLReader can read an STL binary file.

Programs to convert another format to STLB format:

• The C++ program IVCON can read a variety of 3D files and write them out in STLB format.
• The FORTRAN90 program IVREAD can read a variety of 3D files and write them out in STLB format.
• The Visual Toolkit routine vtkSTLWriter can write a VTK image to an STL binary file.

Programs to write a binary STL file include:

• MATHEMATICA includes an Export[filename,object] command that can save a 3D graphics object as a binary STL file.

Sample Files:

• cube.stlb, a cube.

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