12.  Before we re-attach this cross section to our main spline cage, let’s delete an unnecessary spline. Click the Spline sub-object button and select the spline that is coincident with the original spline cage. We don’t need this now; we only needed it in order to copy it and create the side splines that will attach back to the main cage. Press the Delete key and then click Sub-Object to get out of sub-object mode.

13.  Using Select by Name, select the original Spline Cage object. Make sure you’re out of sub-object mode. Click Attach, click the Select by Name button again, choose Shape01, and click Attach to close the dialog box. Notice that the reference surface updates to include the new extension. Click Attach to turn it off. Select the surface reference and press Alt+X to see your model as opaque again. Your model might look something like Figure 5.18.

FIGURE 5.18  The spline model with its new extension

This would be an unnecessarily complex way to model the form we just modeled. We did it to show in a very simple example the technique of detaching splines, Cross-Sectioning, and re-attaching them to the spline cage. On an actual model, you can use this to connect legs to a body for example, and to extrude convoluted quad and tri areas of a spline cage in order to add detailed features such as ears.

Using Five-Sided Patches

In MAX R3, an editable spline has a command called “Bind” that will bind a vertex to an edge. This allows the vertex to move with the edge whenever the edge moves. This feature can also be used to get Surface to recognize what is essentially a five-sided patch. Beware of using this if you plan to convert to a mesh, and especially if you need to export the mesh to another program. When converted to meshes, five-sided patches create strange geometry that does not translate to a .dxf export.

	WARNING Five-sided patches, formed with the Bind feature, create strange geometry when converted to a mesh and exported.

Understanding the Surface Tools Method

What we’ve looked at so far gives us a fair acquaintance with the overall concept of using Surface Tools, as well as some of the techniques involved in the actual modeling work. In the following Surface Tools project, the narwhale, we will use a different technique than detaching splines and cross-sectioning to “extrude.” We will draw new lines and connect them up to the cage by snapping vertices.

Working with Surface Tools on a more complex project involves knowing what you are working with and applying these different techniques as appropriate. Map out your general strategy in your head, before you even sit down to the computer. You want to put more vertices where you need more detailed definition. You want mostly quad patches in your result, so you want the corresponding areas of the spline cage to be defined by four “meeting points” of splines.

At the risk of belaboring the point, it really helps to be savvy with the tools you will be using, because it’s impossible for a tutorial to describe every possible situation you might come across. If you haven’t really grokked the concept of a spline cage and its reference surface, or if you’re unsure of why you might want snaps on or off, for example, it’s worth reviewing the preceding sections before continuing.

Hands-on MAX: Modeling a Narwhale with Surface Tools

Now that we’ve prepared, let’s try using Surface Tools on a project. We’re going to model a narwhale. Let’s start with the spline cage that will serve as our basic structure.

1.  Reset MAX.

2.  Create a circle in the left viewport.

3.  In the front viewport, Shift-drag the circle to the left and choose 6 Copies from the Clone dialog box.

4.  In the front viewport, rotate the circles around the Z axis, moving and scaling them to create an arrangement of circles that looks like Figure 5.19.

FIGURE 5.19  Arrange your cloned circles by rotating, scaling, and moving.

	NOTE If you want to start from here, you can open the file ST_narwhale_1.max on the CD.

5.  Select the rightmost circle. Just to make sure we don’t have any world space transforms applied to the object, click Reset XForm in the Utilities tab. Click the Reset Selected button. This puts the transforms into an XForm modifier.

TIP Reset XForm is a vitally important utility. It’is a good habit to use it as an ounce of prevention, especially when you’ve scaled or rotated an object while modeling. (Scaling or rotating on a sub-object level is fine; it’s just the transforms of the object we’re concerned about.) It won’t make much difference while you’re modeling, but when you animate, left-over transforms can completely screw up your animation. Sometimes it helps to also collapse the stack after resetting XForm. We might not need to reset XForm here; we’re doing it in the name of establishing good habits and thinking about animation while modeling.

6.  Collapse the circle to an editable spline by going to Modify Ø Edit Stack, and clicking Collapse All in the dialog box. (To be on the safe side, choose Hold/Yes when you collapse, although Yes will do.)

7.  Click the Attach button in the Modify tab and then click each of the other circles from right to left in order. Click the Attach button again to turn it off. Our arrangement of circles is now a single editable spline object with seven spline sub-objects.

8.  Apply a CrossSection modifier (Modify Ø More Ø CrossSection if you haven’t customized a toolbar or Modifier set yet). You should now have a spline cage.

Aligning the Spline Cage to Origin

Now we want to align our cage around the origin to make it easier to cut it in half and mirror it.

1.  Create a Point helper object anywhere.

2.  Select the point, click the Move tool, and right-click the Move tool to get the Transform Type-In. In world coordinates, choose 0,0,0.

3.  Select the spline cage and click the Align tool. Click the Select by Name button, highlight Point01, and click Pick. In the Align dialog box, check each axis and choose Center for both Current Object and Target Object. Our spline cage is now centered on the origin.

4.  Using the Select by Name tool, select the point object, go to the Display tab, and click Hide Selected.

	NOTE An alternate way to center the spline cage to the origin is to first center its pivot point within the object by clicking Affect Pivot Only in the Hierarchy tab, and then clicking Center to Object. Then turn off Affect Pivot Only and use the Transform Type-In to move the cage to 0,0,0.

	TIP Assign Hide Selected to Alt+H (Customize Ø Preferences Ø Keyboard). You can then hide an object with a keystroke instead of changing tabs. By pressing 5, you can also unhide by name with a keystroke.

© 2000, Frol (selection, edition, publication)