Getting something to render in 3d isn't that hard, its just that Construct is designed specifically for 2d stuff. Also, theres plenty of really good software programs for making 3d games, such as Unity. Really we'd just be reinventing the wheel if we were to try to make a 3d engine. I've coded a '3d object' that can display obj models that will probably be included in the next build, but its pretty limited. There are so many things a 3d engine should have that Construct just isn't designed for.