Simulate Early, Simulate Often... In Rhino
Resolution sure influence the time of calculation.
Number of surface of the solid? Also this influence the time?
Good question. The answer is somewhat complicated, but a simplified version would look something like this. The two most time consuming steps in the solver is (1) assembly of the linear systems of equations, which involves numerical integration over the Rhino geometry, and (2) solving the assembled linear system using one of the available solvers.
As you pointed out already, both of these steps depend on resolution: the more elements, the larger the linear system, the longer it takes to assemble and to solve it. In addition, step (1) depends directly on presence and number of "small features" in your geometry, which are portions of geometry that have some dimensions that are small relative to the object size. These include slim, thin, and slender geometries. An accurate integration process must resolve these features at run time, and this contributes to longer solution time. Step (2) *may* also be influenced by presence of small features, because they may affect the "conditioning" of the linear system, which in turn affects performance of iterative solvers. The direct solver should not be affected.
Hope this sheds some light on this issues. The number of surfaces of the solid also affects the solution time somewhat, but this factor is much less significant.
ok thank you. My xperience are that lot of small feature influence very much the time. If you like I can send 2 similar object to understand.