You can colour shade or render a surface to display the shape and curvature. Maxsurf has different rendering types available. Each rendering type can be used for different purposes.

See the Maxsurf manual section on Rendering a surface for more information on the different rending options.

We will explore the following surface rendering options:

§   Simple Shading

§   Smooth Shading

§   Longitudinal curvature

§   Transverse curvature

The other rendering options you will see in the Rendering dialog are not useful to display the fairness of the surface and will not be discussed in the LearningMaxsurf training manual.

 View a video that will show you the different rendering options in Maxsurf. [Web | Disk]

Surfaces can only be rendered in the Perspective window.

Ø  In Maxsurf, switch to the Perspective View window

Ø  Open the BasicFairing_SurfaceRender.msd file

Depending on which contours you have displayed, you should see something like this:

Ø  Select Display | Render and select the Simple Shading option from the Rendering Selection dialog:

You should now see something like this:

Simple shading

Note that even though it provides you with good information about the 3D shape, this is not very useful to evaluate the curvature or fairness of the design. Let’s try the next rendering option.

Ø  Switch to Smooth Shading in the Rendering Selection dialog

You will now see something like this:

Smooth shading, black surface colour

This is a lot more useful display to visualise the curvature. Use the slider bars and/or free rotate buttons of the Perspective window to rotate the model and look closely at the light reflecting off this surface. This gives you immediate feedback if there are any lumps or inflections. We can do better though:

Ø  From the Surfaces | Surface Properties, change the colour of the surface to gold by double clicking in the “appearance” square which brings up the colour picker dialog.

Now the surface looks something like this:

Smooth shading, gold surface colour

This is again a lot more useful to visualise any unfairness. The gold colour of the surface reflects a lot more light than the black colour.

Some colours are better than others to visualise surface curvature.

Ø  In rendered mode, you can switch lights on/off. Experiment with switching lights on/off. Ignore the button with the hand icon on the far right.

Ø  Finally, set them as in the image below:

Ø  Again rotate the model in Perspective view so that you get something like this:

By rotating the model and switching lights on/off we have visualised an areas with discontinuous curvature. Let’s have a look at the actual curvature of the surface in this area now:

Ø  In the Rendering Selection dialog, select Longitudinal Curvature

Longitudinal curvature rendering

As you may have read in the Maxsurf manual, the green areas have zero curvature (read: run along a straight line in longitudinal direction) and – if the surface normal has been setup correctly – the blue areas are positive curvature (convex) and the red areas are negative (concave).

What you are looking for are the transitions between for example green and blue or red. Where the colour changes rapidly, there is a rapid change in curvature which usually means unfairness. Changes from blue into red without any green in between are generally undesirable.

Finally let’s have a look at the transverse curvature:

Ø  Switch to Transverse Curvature in the Rendering Selection dialog

Transverse curvature rendering

Notice that this does not show the same areas of green, blue and red. This is because we are now looking ONLY at the curvature in the longitudinal direction. What is clearly visible with this rendering on this model is the transition from the flat of sides to the bilge radius. It is debatable whether – in this case – this is unfairness or a feature of the design.

Exercise:

Ø  Switch rendering off by clicking on this toolbar button:

Ø  Switch all contours off except for Edges and Sections

Ø  Select one of the sections in the midship

Ø  Select Display | Curvature | Show Curvature

This looks a bit messy! Let’s scale down the curvature porcupines

Ø  Select Edit | Preferences and set the Curvature Porcupine size to 5%:

You should now see something like this:

Using a combination of renderings and curvature porcupines you can get a good understanding of the curvature of the surface.

This completes the section on displaying fairness on a curve or surface. Now let’s have a look at some basic fairing tools in Maxsurf that help you adjust the fairness of a design.

Next: Basic Fairing Tools & Techniques.