The importance of reference material is pretty much based on the intent of the project, and the level of accuracy you find acceptable. For the purpose of this tutorial, I'm only trying to achieve an approximation of a mid 50's era Chevy Bel Air. Therefore, I'm only concerned with the general styling, enough to make someone maybe recognize it, but I'm not modeling one that will stand up to the scrutiny of a car fanatic! The level of accuracy you use in your models is up to you, but the principal remains the same. The best reference material I find is the standard 3 view drawings, and as many other photos as you can get your hands on.
I couldn't obtain any predrawn three view reference material, so based on some downloaded jpgs, and an old plastic model kit, I drew my own. A good ruler and a lot of light construction lines can keep details lined up properly... Well enough for the level of accuracy I'm aiming for... Then it's a matter of scanning the pictures and then setting up the references in Cinema.
Those won't win any awards for accuracy or neatness, that's for sure! But it will give me a good start. While they aren't to any particular scale, they were all drawn relative to each other and offer a fairly close approximation of all sides of the car. The technique I use to set up car reference pictures in XL is maybe a little bit stranger than the typical "background picture" approach, but it works well enough for a model like this.
Since our pics are all roughly relative in proportion to each other, I use a simple grouping of plane objects of similar dimensions to the pictures as my reference group. Each plane gets textured with a corresponding reference image and tagged with a quick shading tag so that the reference pics show up using the real time texture mapping capabilities of XL. I use backface culling in all views when referring to this group so that you get a view based feedback of only the pertinent reference image.
The general transparency of the objects allow for modeling to occur even with the planes visible, and gets them a little closer and "in your face" than background pictures. I find it easier to visualize my model this way... You're entitled to use any method for reference you wish, but I've included the sample file here.
Make sure backface culling and quickshading is enabled in all viewports for the full effect!
One other advantage... I think a rendering of this looks freakishly cool all on it's own!!! (Click the image for a better look...)
Now that we're all impressed with our stunning implementation of 3 view drawings, let's move on!