glTF and Construction – Part 2: 3D for Everyone

In the last post we discussed how IFC is a wonderful flexible format but that the flexibility comes at the cost of requiring a lot of resource to display the 3D model. This is because when 3D models are rendered they are always broken down into a mesh of 2D triangles floating in 3D space. Currently vendors use cloud computing to do this processing and then send the pre-calculated model to your devices to view quickly and easily.

The big problem is that each vendor stores and transmits their processed and pre-calculated models in a different way so the only way to view them is using the viewer specific to that format and vendor. We end up with a binding of viewers and storage systems because everyone is using different formats which massively reduces integration and choice for users. Decreasing choice and competition, increasing costs, and reducing productivity.

This is where glTF comes in! glTF stands for graphics library Transmission Format. It is an open format specifically for transmitting processed and pre-calculated 3D models. It is the solution to the problem of the proliferation of proprietary, closed, and restrictive cloud 3D viewing formats.

JPEG of 3D Models

glTF often refers to itself with the tag line “JPEG of 3D models”. This is a very important concept so we’ll have a good look at what this means.

Imagine a graphical designer using Photoshop to edit their images. The Photoshop file will contain many different layers, maybe ultra high resolution parts of images, and lighting settings. But if they wanted to send it to someone to view they wouldn’t want to send the entire Photoshop file because that would mean that someone would need Photoshop or equivalent heavy duty software simply to view it. Instead, they flatten all the layers down into a super simple JPEG file that can be viewed on virtually any device and contains only the data needed to view it.

A JPEG file is an awful lot easier to open and share than a Photoshop file.

In addition to JPEG, further analogies could be:

• MP3: A small audio file rather than a full mixing deck.
• MP4: A small video file rather than an Adobe After Effects file which includes editing and effects configurations.
• PDF: Already very widely used in construction to publish DWGs and Word documents in an easily viewable format.

So, in the future we will be able to add:

• glTF: A simple 3D model rather than a complex layered parametric model.

Viewing Site

Another way of describing glTF is that it is much more for viewing models than editing them. glTF has no parametric features, or blocks, or arrays, or any other complex geometry forms.

This might seem like a serious downside but current trends indicate that simply viewing models is going to become increasingly important, and someone viewing, but not editing, a model doesn’t care about parametric shapes.

Historically, 3D models were mostly used by those actually authoring the models. Of all the people that were using models in some capacity probably about 80% were model authors.

With the advent of clash detection, model reviews, cost and programme analysis, we’re getting more and more people who are using models but not authoring them. Perhaps model authors are now only 50% of everyone that uses models.

The next big stage is rolling 3D out into the field to operatives, the vast majority of whom are definitely not model authors. This will be a watershed moment and once this happens we’ll probably be looking at model authors being as low as 20% of all model users.

In fact, we could even argue that for a half decent modern project we’re already hitting “peak model authoring”. Almost everyone that needs to author models already is (though obviously processes and tech could still be improved).

What this undeniable trend shows is that there is a huge industry requirement to make model viewing far better than it currently is.

What do we want?

To be more specific, what we’re after is a format for 3D models that is:

• Free – allowing widespread license-free adoption
• Open – ensuring the industry’s interests come first, not a specific vendor
• Simple – so all devices can use it with minimal development time
• Supported – so it’s easy and quick to create apps and tools for it

Current Situation

Lets take a look at what is out there at the moment.

Some people use NWD format. It is lightweight but because it is a completely closed and proprietary format that isn’t available on all devices, it can’t be the solution.

Some consider IFC as a “PDF of 3D Models” but the complexity arising from its flexibility means creating reliable viewers requires a lot of computing resource and development time. (though as mentioned in the last post, IFC is by far still the best schema and format for exchanging complete construction and facilities management project information).

There’s obviously also Autodesk’s SVF, Trimble’s BQL, and Bentley’s iModels, which while they may be simple and relatively well supported, they are not free or documented so could never (and therefore should never) become an industry standard.

glTF FTW

Fortunately for us, glTF has been designed to fulfill all the model viewing needs outlined above.

glTF is Free

There are no costs that need to be paid to anyone in order to use glTF.

There’s no one off costs, no monthly costs, no annual subscription, no maintenance costs.

glTF is Open

Here is the full glTF specification on Github: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md

Anyone can read, comment, question, and even propose improvements to it. It has very transparent processes and working groups ensuring it is meeting the needs of industry and isn’t having artificial restrictions put in place to restrict competition.

It is maintained by the Khronos Group, a well respected and established industry group responsible for other formats and APIs. They are the de facto computer graphics standard setters.

A glTF model is unencrypted and generally stored in a plain text format. A glTF model created today in one tool could be opened in a different tool in many years time. Some proprietary formats can barely garauntee being supported just 36 months down the line.

glTF is Simple

In the glTF format 3D geometry is described very explicitly and simply. There’s very little room for different ways of describing shapes, it’s all simple triangles so it’ll look the same in all software. It also ticks the box of being lightweight.

glTF is Supported

glTF already has a very strong ecosystem behind it.

Microsoft have released a number of open source tools for glTF including a C++ glTF Toolkit and a DirectX glTF Viewer. It is supported in Paint 3D and for Windows Mixed Reality.

Facebook allow you to embed glTF models in posts and they’ve released an open source FBX to glTF convertor.

There are importers and exporters for Sketchup, Unity, 3DS Max, Maya, Unreal, and Blender.

There are command line converters for DAE and OBJ. There are utilities for JavaScript, C#, C++, Java, Go, Rust, Typescript and more.

Rather than list them all here, I highly recommend you take a look at the frequently updated glTF resources page to see the full plethora of free tools available: https://github.com/KhronosGroup/glTF/blob/master/README.md#gltf-tools

glTF is arguably the single best support modern 3D file format.

DWG Dodos

Back in the day DWG had many alternatives too but none ever really took off so why is glTF going to be different?

Primarily, DWG had the backing of a single major industry player but the combined support that glTF already has dwarfs any single construction company’s influence.

Secondly, DWG alternatives had only a few software tools available for developers, making adoption difficult and slow. As shown above, glTF already has so many resources that one can jump in and be making apps based on glTF in an extremely short space of time.

Lastly, the construction industry used to be rather technically illiterate and would take at face value any technology it was given, but with the increasing digitisation the construction industry is becoming much better at understanding the importance of data and open formats. While it has taken a long time, the construction industry is finally realising open data isn’t just something for hippies but is vital for innovation, business, and productivity.

So what are some of the more concrete examples to show exactly how glTF can fit into the construction process? Find out in Part 3, the final part of this series!

Summary

In this post we looked at:

• The concept of “JPEG of 3D Models”
• The growing need for a viewing format
• A file format would need to be free, open, simple, and supported
• What is out there at the moment
• How glTF would meet our model viewing needs
• And why glTF will succeed despite how in the past DWG alternatives failed

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