A computer implemented method for determining a silhouette volume of a 3D object, e.g. for mesh simplification, comprises: receiving a computer representation of a 3D object; determining a silhouette volume of the object, wherein the silhouette volume is the maximal volume of space having a silhouette from every viewing direction which is identical to the silhouette of the object from the same viewing direction, and wherein points of the object which lie on the boundary of the silhouette volume also lie on the boundary of the object's projected silhouette from at least one viewing direction; determining, based on the silhouette volume, the extent to which features of the object are silhouette features; determining, for a plurality of planes and for a plurality of different axes, at least one intersection loop, wherein each intersection loop corresponds to a planar cross-section of the boundary of the object in its respective plane; and determining the convex hull of each intersection loop.