The Disney BSDF [1, 2] is extremely flexible and offers a lot of artistic freedom. The only real limitation is that the BSDF is required to be energy conserving

The Disney BSDF [1, 2] is extremely flexible and offers a lot of artistic freedom. The only real limitation is that the BSDF is required to be energy conserving, but that's hardly a limitation. A physically-based renderer is still able to produce non-photorealistic results. [1] http://blog.selfshadow.com/publications/s2012-shading-course/burley/s2012_pbs_disney_brdf_notes_v3.pdf http://blog.selfshadow.com/publications/s2012-shading-course... [2] http://blog.selfshadow.com/publications/s2015-shading-course/burley/s2015_pbs_disney_bsdf_notes.pdf http://blog.selfshadow.com/publications/s2015-shading-course...