Here are a couple of automotive headlight assemblies 3D printed using a combination of 3D printing technologies. The headlight enclosure is printed using Selective Laser Sintering (SLS) using a rigid material, whereas the lens is printed using Stereolithography (SLA) in a transparent material. You can still see the build lines on the lens. But after a bit of polishing the lens becomes as transparent as glass. These parts are mounted on prototype vehicles to check form, fit and sometimes even function.