A Comparison of GCODE and STL File Formats
Here we will look at both the GCODE and STL file formats and compare their features to try to work out what format is best to use for a given situation. Before we begin, if you're not familiar with 3D modeling and the terminology behind it, we thoroughly recommend this great article that explains 3D modeling concepts and the terminology that goes with it.
Structure
GCODE isn't strictly speaking a 3D model format in the traditional sense; rather, it is a format that is used to describe to 3D printers how to build an object by providing low-level instructions such as "move to x,y", "begin extruding", "move to x+10,y", "end extruding" etc. If a GCODE file is opened in a text editor, there will be hundreds, if not thousands, of these commands.
The STL format, on the other hand, is a 3D mesh format that is a simple, fixed format for storing triangles. STL files come in either text or binary formats, with the binary format preferred due to the large file sizes of 3D models stored in the text version.
Supported Material
GCODE files do not directly contain material information; they do, however, contain commands to tell the 3D printer to switch filament, allowing objects to be printed using more than one color/type of filament. With STL files there is no official support for materials; all mesh data contained within an STL file must be the same color.
A sample GCODE file preparing to 3D print
A sample GCODE file preparing to 3D print
A plain STL file
Editing
GCODE files are not designed to be edited directly; any edits should be applied to the source 3D model file and re-exported to the GCODE format. The STL format, on the other hand, is easily edited and is supported by most 3D modeling applications, and crucially, it is also supported by most 3D printing slicer software, making it the perfect format for generating a GCODE file from.
File Size
With GCODE files, they can be either text or binary, though the text format is generally the more common type. Within the GCODE text is a list of commands, and due to the number of commands needed for even a simple 3D model, these files can become very large. STL files can also be binary or text, and the binary format is usually the most common type. The contents of an STL file are quite simple; a 3D model is composed of a list of triangles, each of which is described using 3 vertices. Compared to other 3D file formats such as GLB, this is an inefficient way to store the data; however, it means it is easy for 3D modeling and slicer applications to implement support for the STL format.
Summary
For sending a 3D model directly to a 3D printer without needing a 3D slicer program, then GCODE is the preferred format; all other 3D formats, including STL, will need to be run through a 3D slicing application before 3D printing.
