Adding paths (Curves)

Adding shapes in Maya is as simple, and similar, to adding and primitive mesh. You can use the top drop down menu via "Create > Your Chosen Shape" or through the curves tab on the main shelf above the viewports.

Either way you should be aware of the different kinds of curves in Maya. The first tools you'll see in the curves tab, and the type of curves used by the basic shape creation tools, are "EP" curves. These are more akin to b-spline curves where the control points simply "influence" the shape of the curve.

You can also create Bezier curves which may be more comfortable if you are familiar with using them in Adobe Photoshop, 3DS Max, or Cinema 4D. Which you are. The "Bezier Curve Tool" is the last one listed on the curve tab.

If you have started an object with the EP curves and wish to switch to Bezier this is possible through "Modify > Convert > NURBS curve to Bezier". This way you can take advantage of control handles to help shape the object.

Thankfully most of the surface operations, such as extrude or bevel, can be applied to Bezier paths just as well as EP paths.

The actual process involved in making the path will depend on the type you've selected. EP curves for instance can simply be clicked into existence once at a time. Bezier curves will of course use the "click and drag" method familiar to other programs. Experiment to see which one best suits your needs.

Working with paths

Now let's look at the different kinds of paths and how you can modify them.

The "create square" tool

Before discussing how to edit a curve or create surface geometry from one there is one thing that needs to be said that can cause problems for many people. The "Create Square Shape" tool in the Curves window does not actually create a square. Because Maya hates you it actually creates 4 straight lines within a group. If you wish to use this tool and form a single shape then after creation select all four lines and choose the ADVANCED options of "Edit Curves > Attach Curves". By clicking the little square near the option you can bring up a dialogue that allows you to select "connect" instead of the default "blend". This will retain the shape of the square and make it one continuous line.

Keep in mind it still will not be made up of just four points but have the default 3 segments per line.

If you do not take this into account and try to add, for instance, an extrude surface to the square. The result will be a shape with 4 walls shooting off in various directions instead of a swept square shape.

Common operations

Here are the most common operations you'll probably want to make use of while working with curves.

To close or open a curve:

Make sure you're in "surface" mode and go "Edit Curves > Open Close Curves". Remember that you can NOT be in control vertex or any other edit mode. You must be in object selection mode for this to work.

To continue a bezier path that has been started:

While in vertex contorl mode simply select he bezier tool from the shelf again and click on the last point in the path. If you want to extend a new segment from the beginning of the path you'll have to reverse the path first.

To reverse a path:

While in the "surface" layout mode go to "Edit Curves > Reverse Curve Direction".

Making surfaces from paths

Once you've made the curves you want to use as the base of an object you can use the options in the "surface" tab of the main shelf to create actual geometry.

Make sure you are in object selection mode when applying a surface operation to the selected curve. You can not be in control point or any other sub-object mode when creating a new surfaces.

Like most all compound functions in Maya the order of selection influences the final shape. For instance the steps for an "extrude" object would be as follows...

  1. Select the curve that defines the SHAPE of the object first (This will also serve as the starting point of the new geometry).
  2. Select the curve that defines the DIRECTION of the object second.
  3. Click the appropriate shape creation function. In the curve shelf, for this example, the "extrude" icon near the center as shown here.

At this point a compound shape will be made and added to the outliner as a "surface". At any time click the original curve object to edit the control points as normal. The changes will automatically reflect within the surface geometry.

If the result of your new object shows a black surface then the normals are probably facing the wrong direction. You can't choose "Normals > Reverse" from the drop down menu either since the produced object is a surface and not a polygonal object. You have to change the menu layout to "surface" and then choose "Edit Curves > Reverse Curve Direction" from the drop down menu while the curve that made up the PATH is selected.

Also note that by default the paths may not be affecting the curve as expected. The position of the entire path curve may change the scale of the surface geometry. If this is an undesirable effect then you'll need to find the "extrude" attribute within the surface shape and under the "extrude history" section change "closest endpoint of the path" to "component pivot". Finally you can try to switch on "fixed path" in the same section to retain proportions between the input curve and the result.