Longitudinal and transverse stiffness

I have recently posted a question regarding t encountering a problem on bumpy surfaces when importing IGES files from Autocad surfaces.

I have just now discovered that the lumps and bumps can be controlled by double-clicking the individual surface which brings up the "Surface Properties", under "Stiffness" and by adjusting the longitudinal stiffnesses the software will alter the level of bumpiness on a particular surface.

Choosing "2" will give me a very sharp spike while choosing "4" will give a relatively smoother bump.

I can see the menu can have different levels to be selected and goes all the way to "10". However, the maximum I can choose here is only "4" and is the default value.

Does anyone have any idea on how I can level this up to "10" please?

Thanks in advance.

  • Hi Arthur,

    I'll answer your question about stiffness first - then come back to what I think the problem is.

    Yes - a higher stiffness will smooth out the surface, but it will also change the shape of your surface

    Think of the stiffness as being the order of the polynomial defining the curve through the longitudinal / transverse directions. If you have 2 points, you can only fit a linear curve through. 3 points can fit a quadratic curve etc.

    So the highest stiffness you can have is the number of control points in your net in that direction. Mathematically, you can't have more.

    Where I think you have a problem is that you have control points in the middle of your surface that aren't in the right spot. If you turn on Display | Net | Show Net then you'll see that you have control points making the surface that shape. If you want to smooth the surface, then move the control points that are making it unsmooth.

    I'm not sure why it would be coming in with the surfaces different from AutoCAD. Is the scale of your model realistic? i.e. did you design your ship in metres but imported it as milimetres, so your model is now 30mm long?

    you could try saving a microstation or Rhino file from AutoCAD and importing that instead.

    regards,

    James