In black-figure vase painting, the pre-drawn outlines were a part of the figure. In red-figure vases, the outline would, after firing, form part of the black background. This led to vases with very thin figures early on. A further problem was that the black background did not permit the depiction of space in any depth, so that spatial perspective was almost never attempted. Nonetheless, the advantages outnumbered the disadvantages. The depiction of muscles and other anatomical details clearly illustrates the development of the style.