A question that comes up in almost every project and every new collaboration is: “But we already have 3D models, can’t you just use those?” A fair question — why rebuild something that already exists?
Almost all products are fully designed in 3D before they’re made. This allows every detail to be thought through, connections and forces to be tested, and the technical drawings and exports needed for production to be created.
So for almost every project we take on, a detailed 3D model of the product already exists. Great, of course — but not perfect. In the 3D world there are basically two ways to build models: CAD models and polygon models. And of course, production models are built in CAD, while we work in polygons.
Two different purposes
You can compare it to English vs Chinese, or centimetres vs inches. They serve the same purpose at the core, but they’re completely different systems. CAD models are great templates and tests for real-world scenarios like construction or manufacturing. We work in 3ds Max, which is a polygon-based tool focused on visual output and efficient use in things like games, VR, and photorealistic visualisations.
CAD models are built for precision, fabrication, and technical calculations. Perfect for the production process. It’s all about exact dimensions, tolerances, and making a product manufacturable.
Polygon models are built for visual quality and performance. Ideal for realistic renders, animations, and VR — with lifelike details such as stitching, weld seams, and textures.
There are many more types of 3D models, but we won’t go into them here. Curious? Then read our story where we explain the different kinds of 3D models.
Why create our own 3D models?
When we want to use a CAD model, we import it into our own software and convert it into a polygon model. That conversion is far from ideal. It’s a bit like the early translation programs: if you translated a text from Dutch to English, you ended up with an English version, but it was full of errors. The same thing happens when converting a CAD model into a polygon model. We do get a 3D model in our software, but it’s full of flaws and limitations that affect the quality of the visuals we create. By building the models ourselves, we ensure a clean, reliable result that we can use for years.
What goes wrong?
In de conversie zijn er een aantal dingen die fout gaan maar daarnaast is het model is ook onbewerkbaar, ofwel wij kunnen zelf geen aanpassingen meer doen aan het model. Wat ons beperkt in de mogelijkheden die we hebben. Hieronder een overzicht van de gebreken van een CAD model in een Polygon programma. Details die het verschil maken in de overtuiging van de visuals.
Textures
With a CAD model, we’re very limited in how we can place and control textures. In the example above, the wooden legs are bent into that curved shape, so the wood grain should follow the curve as well. That’s simply not possible with a CAD model.
Lage kwaliteit
The import resolution of a CAD model is lower. Because of that, rounded shapes often turn into visible, blocky segments — like the tabletop in the example above.
Mistakes
During conversion, things can break. CAD models suddenly end up with holes in odd places or parts that no longer line up. Often they’re tiny gaps, but they still stand out in a final render.
Details
A CAD model is fixed — we can’t change anything about it. That also means we can’t add details like welds or stitching. Exactly the kind of details that make a product look realistic.
Chamfers
In real life, perfect 90-degree corners don’t exist — everything has a slight curve or bevel. In CAD, those sharp corners do exist, and we can’t adjust them. That means you lose a layer of realism, because those tiny roundings create the subtle highlights that make a product look real.
Too much information
A CAD export includes everything — even the things we don’t need at all. Often there’s internal structure or technical details that will never be visible in a render. But they still end up in the file, eating memory, slowing down the software, and increasing render times.
Inefficient files
Inefficient 3D models lead to much larger file sizes — sometimes imported CAD files are up to ten times bigger than a polygon-built model. This slows down the 3D scenes, causes more crashes, and increases render times.
Production processes
CAD models are production models, but the way a part goes into the manufacturing process isn’t always how it comes out. Take a pressed seat or shell, for example — it often springs back slightly after pressing, creating softer curves and edges. We can’t reflect that in a CAD model, which means products in the visuals may look different from the real product.
When do we use a CAD model?
There are moments when an existing CAD model is the most practical choice. Tight deadlines may leave no room to build a new model from scratch. And for a few simple wide shots, that extra level of detail isn’t necessary.
Sometimes it’s simply about balancing cost and value. For older products that are nearing the end of their cycle or are less important within a collection, investing in a fully rebuilt polygon model isn’t realistic, even though images are still needed.
There are also projects where speed or volume matters most — for example, visualising a large number of products at once for a catalogue. In those cases, production models are the fastest and most efficient option.
In these situations, a CAD model provides a solid base to quickly reach a “good enough,” usable final image.
In short
CAD models are built for production, not for visual quality. When you convert them to polygons, you immediately run into errors and limitations that show up in the final images:
- Close-ups lack the small details needed for a realistic result.
- Textures and prints are restricted in how they can be placed.
- Large scenes and animations become heavy and almost unworkable.
Total shots are usually fine — but that’s about it.
CAD is perfect for manufacturing, not for photorealistic visuals.
Conclusion
CAD models are essential in the design and production process, but they’re not ideal for realistic 3D visualisations. When converting CAD to polygons, you end up with a model that’s technically correct but full of limitations. Details get lost, textures don’t map well, and the heavy geometry slows down the software and increases render times.
That’s why we prefer to rebuild our models in polygons. We use the CAD model as a reference, giving us full control and allowing us to add every detail needed for a photorealistic result.
Still, there are moments when a CAD model is the right choice — for example, when deadlines are tight or when only a simple wide shot is needed and the investment in a fully rebuilt model wouldn’t make sense.
In the end, it’s about what the project needs: maximum image quality with a custom polygon model, or speed and simplicity with an existing CAD model.