Triset is a geometry, which consists of a number of triangular faces. Faces usually share the vertex data: connected triangles can refer to same 3D vectors. Each corner of a triset face has its own private normal vector. Normal vectors can be adjusted to achieve sharp or smooth looking shading over face boundaries.
Triset is much simpler object as the Subdivision object. It is also much more memory efficient. Its main function is to represent imported polygonal objects. If a triset geometry needs advanced editing, it can be converted to the SDS form, edited and then converted back to the efficient triset form.
Triset property gadget has the following controls:
Phong Fix: Controls how rapidly illumination is faded towards the surface tangent. Normal interpolation of triset faces does not look smooth when ray traced illumination hits the surface at low angles, because the polygonal surface geometry starts casting shadows and blocking the illumination. By fading illumination at low angles, these shading errors can be made less visible.