2D and 3D are both vector (as in, a mathematical description of the shape). Typically when we say "raster graphics", we mean graphics already computed as a set

2D and 3D are both vector (as in, a mathematical description of the shape). Typically when we say "raster graphics", we mean graphics already computed as a set of points, like a bitmap PNG file. But here 2D comes in as a set of curves, and 3D comes in as a set of triangle edges. Both are mathematical descriptions that have to be "rasterized", e.g. transformed from the edge representation to the raster one.