To keep this tutorial short I will not show you how to do the whole car, but just the bonnet (hood) for this tutorial, as the same technique can be passed on to the rest of the car. Now create a HyperNurbs object. 
As a child object of the HyperNurbs create a Symmetry object. 
As a child object of the Symmetry object, create a Null Object. 
As a child object of the Null Object create a Polygon Object. 
In your Objects panel you should now have this: 
Make sure Points mode is still selected. 
Now go to Structure » Add point, hold down Ctrl and left click where you want the first point, do this in Top view at the very bottom of the bonnet (hood). If you are using my BMW blueprints, then start it just above the radiator vents on the front, as the radiator can be created later on once we have the rest of the bonnet (hood) completed. For this first point it is EXTREMELY IMPORTANT that the X co-ordinate is set to 0. Once your point is in place select the Live Selection Tool. 
And select the point we just created. Now right click anywhere in the viewport and select Clone. 
Now in the panel to the bottom right (I think it's called the Attribute panel), use these options: 
This will clone your point in the exact same position. Now in the Side viewport move it so it follows the contours of the car. You want around 6 or 7 points up to the window. So just repeat the process of cloning, you can do more than 1 point at a time but I recommend you do one at a time for the first line. Remember to keep the points at the X co-ordinate 0. This is extremely important. You should now a your first 6 or 7 points set up in a row, keeping to the shape of the car. 
Now select all of the points, and clone them. Move them over to the left and put them in their correct positions. 
This is where I found out that my blueprints are either incorrect or aren't aligned properly. As you can tell from the Top and Front view the right hand set of the points are completely misaligned. I will carry on anyway just to show you the technique. So now we have our points set up we can start to make it look like a bonnet (hood). Right click and press Bridge or just press the B key. Left click and hold the mouse button on the very first point we made then move the mouse over to the point to the right. Then let go. This will create a bridge between the 2 points and will be represented by a yellow line. Do the same again but for the next point up. This should create a rectangle using the 4 points. 
Now continue this process holding the mouse button and creating polygons until you get to the top of the car. Then press the Spacebar. This will finish the bridge tool. 
Repeat this for the rest of the points to finish off your bonnet (hood). If you look in your perspective viewport, you should see something that resembles a bonnet (hood) although it is hard to tell as the rest of the car isn't there. 
To make sure the bonnet is as smooth as possible, go to the Object panel and select the Polygon object. Then go to File » Cinema 4D Tags » Phong. 
If you look at your Perspective viewport again you may see this areas that have changed shade. 
So we need to realign the normals to make it smooth. Select the Polygon mode from the left. 
Then press Ctrl + A on your keyboard to select all the polygons. You may notice that some of the normals are pointing in different directions. The normals are the yellow things in the middle of the polygons which show the direction of the polygon. On my model you can see that the normals are pointing opposite directions which caused the different shading when we applied the Phong tag to our Polygon object. 
To realign them, keep all the polygons selected then go to Functions » Align Normals. 
This then changes the normals so they all align properly. 
Then you can render it, and see that it is nice and smooth. 
Use the same technique and just more points on covering up more of the car. Remember to be patient, it does take a lot of time especially at first. 
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