How big was a marsupial sabertooth? Establishing relative size in a scene
As some of you have already noticed, many of my sketches are crossed by a multitude of lines, whose purpose may not be clear at first sight. Well, all of them have a purpose, although not all have the same one. Some sets of lines are there to serve as a sort of grid, to make the composition more easily replicable. Others are there to show me more clearly the proportions of the working rectangle while I build the composition, so I can check if the elements are balanced. Finally, some lines are there to establish a persepctive in order to control the relative size of animals and objects in the scene. For this purpose I normally create a one-point perspective with its vanishing point in the horizon.
Such a simple procedure gives me a pleasant sense of relief regarding doubts about how big or how small one animal species would look beside another, and some times the results are surprising, even though I have the measurements and know the dimensions of the animals beforehand.
One example is the preliminary sketch I did for a scene showing a pair of marsupial sabertooths of the genus Thylacosmilus, together with some glyptodons and ground sloths. In my very first sketches I tended to show the distant sloths and glyptodons as rather larger animals, but when I put my perspective lines in place I found that these animals would have to look rather less impressive. After all, these Pliocene edentates were way smaller than their later, gigantic relatives from the Pleistocene. The composition lost some spectacularity but gained in accuracy!