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To turn a photograph which looks real into a portrait which looks like a drawing we need to use a technique called NPR which stands for Non-Photorealistic Rendering. This is just a posh word for saying turn a picture into a line drawing. Here is an example:

The next major step was to take the face in our photograph and determine which features needed to be caricatured. How do we do that? well, first we need to determine what an "average is" face? For that Dr. Marquardt created a mask which uses the Golden Ratio as a measure to determine the extent of beauty in a face. The closer the face matches the mask the more beautiful the face is. Look at the image below and how closely Tom Cruise and Nicole Kidman's face match the mask

So now that we know what needs to be caricatured all we need to do is to use a technique called warping to make these features bigger or smaller. However, we need to make sure that we do not go against the grain of the face so if a person has a big nose we can't make it smaller otherwise we wouldn't be able to recognise him or her!

In the next section we explore the details of NPR and the Golden Ratio. Click on the link below if you want to learn more!