What is an STL File? Pros and Cons and When to Use It

Two decades ago, 3D modeling was something that only experienced animators and game developers bothered with. 3D models were nothing more than digital representations of objects, real or imagined, that had depth. Nowadays, technology exists that can turn a 3D model into a real object – and vice-versa. 3D modeling has also become so common and accessible that people are doing it just for fun.

As with any piece of digital data, 3D models are stored in file formats that can only be opened using the appropriate software. The STL file format is one of the more commonly used for 3D models for several good reasons. What is STL and why should you be using it?

Where did the STL file format come from?

STL stands simply for “Stereolithography.” It is a native file format of the CAD stereolithography software that was developed by 3D Systems. It is also one of the oldest 3D file formats – dating back to the 1980s.

A problem that has plagued the 3D modeling industry for decades is the vast number of different and incompatible file formats of 3D models. This is the result of each 3D software developer coming up with their own proprietary formats. Nowadays, there more than a hundred of these file formats floating around online, making collaboration between different systems difficult.

The most common way to work around this difficulty is to stick to “neutral” or “open-source” file formats. The file formats are industry-standard and can be converted between the different proprietary formats, allowing them to be opened using any 3D modeling software. STL is an example of an open-source format. There are a few others such as OBJ, IGS, and STEP.

How is it different from other 3D file formats?

In the field of 3D printing, the STL file format is one of the two popular file formats used, along with OBJ. Between the two, STL is the much simpler alternative, giving it a wider user base. STL files are smaller, making them perfect for sharing and publishing.

There are a couple of things that make STL unique. The first is that it’s a tessellated format, which means that it approximates the surface of a 3D model using a series of interlocking triangles. This “triangular mesh” technique is the most common method used in 3D modeling.

Despite the simplicity, the resolution of an STL file can be enhanced by simply increasing the number of triangular planes that approximate a surface. Naturally, this increases the file size of the 3D model. Even at the highest level of resolution possible for a tessellated file, a 3D model saved in STL format still has lower fidelity than those that use precise surface encoding.

Pros and cons of working with STL files

The STL file format isn’t the absolute best there is. It’s great for 3D printing, but you won’t see a lot of serious 3D artists working with “simple” STL files. If you’re trying to decide whether to save or share your files as STL, here are the benefits and limitations of doing so.

PROS

1. Easy to share and publish

If you look at any site that publishes 3D models, you’ll notice that a lot of them are in STL format. The simplicity of STL files keeps their sizes small. They may lack the fidelity of other file formats, but most 3D printers are similarly limited in the level of detail they can recreate anyway, so it hardly matters.

2. Compatible with practically all 3D modeling and printing software platforms

STL has been widely accepted as the standard file format for models meant for 3D printing, so manufacturers of 3D printers have designed their products to work with it. Almost all 3D modeling software platforms can open STL files, with some even developing a “light” version of their platform meant exclusively for working with STL. With a large user base that relies on the file format, technology for working with STL is likely some of the most mature in the field of 3D design.

3. Acts as the interface between 3D modeling and 3D printing

Full-fidelity 3D models created using CAD software are impractically complex for sharing online, more so for 3D printing. Converting to STL is a way to “simplify” the model to a form that can be easily understood by a printer’s slicer software. There are even some 3D printer models that don’t work with any other file format aside from STL.

CONS

1. Does not contain texture data

A standard STL file merely contains data on the vertices of the triangles that approximate the surface of a 3D model – nothing else. This means that an STL color does not contain color, texture, or material to be used. If you want to print a 3D model using multiple colors or materials, then an STL file is not the best choice. It’s also not possible to embed metadata, such as copyright information, in an STL model

2. STL files are very hard to modify

A major disadvantage of an STL file is that it can be very hard to edit outside of simple scaling of the model. Since an STL model only contains an approximation of the original 3D model and not the model itself, it’s often easier to start a model from scratch than to modify an existing STL file.

Although we list this as a limitation of STL, some publishers of 3D models actually use this characteristic to their advantage. Since STL models are notoriously hard to work with, it also means that the models they publish cannot be modified. In a way, they retain ownership of their original models, even if the STL version has been published for everyone.

3. Might not catch up with modern 3D printers

We’ve mentioned how the limitation in the fidelity of STL files is tolerable when we consider how today’s 3D printers are similarly limited in resolution. However, this may not be the case moving forward. Even today, modern 3D printers with micron-scale resolution are already being developed. If these 3D printers start to become the industry standard, then tessellated formats like STL may soon find themselves obsolete.

Final thoughts

If you’ve spent any time playing around with 3D models and printers, then you’ve probably already encountered STL files. This remarkably compact file format is excellent for sharing 3D models, but it does have a couple of limitations. By understanding these limitations, you’ll know what you can and cannot do with STL files – and when you need to start working other 3D File formats.