Choose one of the following techniques to control fine displacement. These help you avoid the risk of accidentally creating billions of triangles until memory runs out, without juggling a large number of displacement-mapping parameters.
When you use Fine approximation, you must choose one of these techniques:
Specifies that all triangles should be subdivided until they are smaller than edge pixel diagonals. The edge value is typically around 0.5, or 0.25 or even 0.1 for very high quality. This technique is recommended for all fine approximations.
Specifies that the triangle edge length should stay under edge units in the object's object space. The edge parameter needs more careful tuning than in the view-dependent case, and very high values defeat the purpose of fine approximation.
Tessellates a free-form surface such that all microtriangles have the same size. This results in very regular meshes but is harder to optimize, and may use significantly more memory.
This lets you define triangle size as a fraction of the surface size, instead of in object or screenspace mode.