is used to hold the coordinates of a region in 2D defined by a closed polygon represented by a comma separated list of coordinates in the form "x1, y1, ..., xn, yn" where each (x,y)-pair defines a point of the closed polygon in absolute pixel coordinates. In 3D a solid is represented by a closed set of surfaces where each surface is defined by a closed polygon/region in 3D space, given in the form "x1, y1, z1,..., xn, yn, zn" where each (x,y,z)-triple defines a point of the closed polygon. All surfaces must be defined such that they share every boundary segment with one other surface.