1. A method performed by one or more processes executing on a computer system the method comprising: distributing a plurality of sample points across the surface of a 3D object model to be rendered into a 2D image; determining a solid angle subtended by a first sample point and a second sample point relative to a region on the 3D object model; and depending on the determined solid angle relative to a threshold value, selectively using for rendering a portion of the 2D image either a previously determined subsurface scattering contribution for the region or a newly determined subsurface scattering contribution for the region.