Generally speaking, they are slow. Something has to convert the precise, accurate mathematical models into something that video hardware can display. Some video cards and advanced APIs can build objects out of things other than polygons, calculate smooth curves, and the like, but by far the most common workflow in the VR and game industry revolves around polygons and textures.
We can, therefore, take polygons as a given. Modern video cards, and high-end cell phones have quite a lot of capability when it comes to rendering objects, although to maintain frame rates for VR, we do have to pay attention to the number of polygons.
The good news is that, you can make very good looking VR objects for ...
