We were asked to create a character using an adventure time style making them look like they have volume without using shading or detail. The characters are made up of simple shapes such as cylinders that show perspective clearly. By making the ends of the arm convex it shows that the arm is facing away from the viewer and concave would indicate that the arm or hand is coming towards the viewer. My character has baggy clothes that show the fabric hanging off and wrapping around the character.
Usually volume can be shown using shading to indicate things curving or perspective indicated by objects around them.
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