i want to know how we can design car surface in nx .
Basically apply raster image in the model and scale it to match the real thing you're modeling. You can place them to cross each other or to create a box of the raster image planes. In the video the raster images are crossed and in my projects the Lotus 49 is created by making a box of the images. It's what you prefer. But the video tells how to get started. Remember to use .tiff images.