Choosing Orca3D Mesh Settings

The Orca3D mesh settings are used both for hydrostatics calculations (including real-time hydrostatics) and for the real-time sections computations. For more accurate hydrostatics you tend to want finer mesh settings (i.e. producing denser meshes) while often times you want somewhat coarser settings for the real-time calculations to enhance speed.

In our early Orca3D hydrostatics tests with a somewhat limited set of hull shapes, we had obtained good validation results using a mesh density of 0.7 with all other mesh options turned off. This is the default in the Orca 1.0.14 release. Later we found the results to be very dependent on the geometry being analyzed. As a result, for the next release Orca3D we have changed the default mesh settings to be finer. Instead of a custom setting with a density of 0.7, we have changed the default to "Smooth and Slower" which sets a mesh density of 0.8 and also turns on "Refine Mesh". To date we have found this to be a better choice for hydrostatics over a wider range of hull shapes. You should be able to choose this option in the current Orca release. (Note that setting a mesh density greater than 1 has no effect.)

It is difficult to specify a mesh setting that is appropriate for all Rhino geometries because of the wide variation in shapes and topologies that can be created. If you don't find the "Smooth and Slower" option to be adequate, the next thing to look at is changing back to "Custom" (which should retain the previous Smooth and Slower settings) and consider entering a non-zero value for "Max distance, edge to surf". The default value of zero just turns this option off completely. Be careful about specifying too tight of a tolerance here or the Rhino mesher could take a very long time. Orca does not currently display the resultant mesh but since we use the Rhino mesher you can see the same result by using the Rhino Mesh command which has the same controls.