Have you ever tried to design a logo or icon that displays an object in 3D? If you did, you would know how difficult it is to accurately draw a 2D projection of a 3D object. What is more frustrating is if you want to draw same object as seen from different camera angle in 3D, then you have to start over from scratch.
For example, let’s say you are creating an illustration of a Formula 1 car for a client of yours in Inkscape or Adobe Illustrator (or Photoshop/Gimp). You assume the camera looking from front right side of the car at level angle. When you show your work to the client, he says he was hoping for a view from front left side of the car and looking below, so that the interiors of cockpit will be more visible. You will have no choice but to start from scratch.
Therefore it makes sense to model such a car in a 3D model editor and export its different views in 2D file formats for further editing.
Now 3DTin lets you export a 3D model in SVG – a standard vector image format. You can then import the SVG into Inkscape or Adobe Illustrator to add advanced effects.
For example, consider this Formula 1 car created by felipe denar on 3DTin. I modified it a bit and saved it in two different views (same as I described above), then exported them as SVG images and opened in Inkscape.
If you were to draw these two images without any help of a 3D modelling software, you would have to draw both of them from scratch. But with 3DTin you can simply rotate the view, save the sketch and download another SVG image.