Every project starts from sketches. I do lots of skeches before starting modeling - it helps to visualize not only model itself, but also problems which might arise during modeling or animation process. But for toonish character like that I use just side view skech for modeling. So if you have your sketch ready ( make background light grey, it will be easyer to see in workspace window) choose Panels >Ortograhic > side view, then go to View > Camera Attribute Editor and click on Environment. There you will see a button - Create image plane, click it and point to your sketch image file. ...

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