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# 3D Modeling Basics

This chapter is from the book

## Deforms

You've learned how to move, scale, and rotate things; now it's time to apply some torque to them. Deforms such as Bend, Twist, Skew, and so forth, enable you to easily alter primitives and other objects in subtle or dramatic ways.

NOTE

If you aren't using a parametric modeler to do your deforms—or if you plan to collapse the object down to editable mesh—you may want to save off a version of an object before you apply a bend or twist to it. These sorts of deforms are very difficult to alter later in the modeling process if you find you need to make an adjustment.

Like transforms, deforms may be affected by axis constraints, the current coordinate system, and the pivot point settings. They may have additional parameters of their own that also affect outcome, such as an independent center point. In addition, deforms are affected by the resolution of an object. If the object on which you're performing a deform operation doesn't have enough steps or segments, the result won't be satisfactory (see Figure 3.30). This means you have to think about how you will be modifying an object at the time you create it to ensure that you will be happy with the results later on, when you apply the deform. Clearly, this is one of the reasons why spline and parametric modeling is so popular—they enable you to adjust the resolution of an object at just about any point.

FIGURE 3.30 The effects of object resolution during a deform. (a) Cylindrical primitive with no deformation applied. (b) Bend performed on a single-segment cylinder. (c) Bend on a 3-segment cylinder. (d) Bend on a 10-segment cylinder.

### Bend

The Bend deform distorts an object evenly around the selected axis. As the student in this chapter's opening story discovered, Bend requires some planning if you expect to do other deforms on the same object. This is because when you bend an object, it no longer conforms to one or more of the axes you might need for a later deform, such as a Twist. Therefore, Bend is often one of the last deforms you do to an object to distort it into the finished form. Also, Bend may be affected by the coordinate system, the axes constraints, and the position of the object's pivot point (see Figure 3.31).

FIGURE 3.31 Bend distorts an object around an axis. (a) The base object. (b) 90-degree bend with pivot point at base of object. (c) 90-degree bend with pivot point in center of object.

### Taper

The Taper command compresses and expands an object along the selected axis. Taper may be sensitive to coordinate setting and axis constraints, as well as the position of the object's pivot point, because Taper uses it as a sort of fulcrum for the operation (see Figure 3.32).

FIGURE 3.32 Effects of pivot point location on Taper: (a) The base object. (b–c) If the pivot is at one end of the object, that end is unaffected. (d) If the pivot is centered in the object, both ends are affected in opposite ways.

### Skew

Skew forces one side of the object in one direction along the selected axis, and the other side in the opposite direction. This is akin to putting your hands on the sides of your face and pushing up with your right hand while pulling down with your left. Like the other deforms, Skew may be affected by the coordinate system, the axis you have selected, and the pivot position (see Figure 3.33).

FIGURE 3.33 The effects of Skew (the affected object has been scaled a bit larger than the original for clarity): (a) Skewing on the X-axis. (b) Skewing on the Y-axis. (c) Skewing on the Z-axis.

To be sure, Skew probably isn't going to be one of your most commonly used operations. It does have its uses, although you can often attain the same results with other tools, instead.

### Twist

Twist winds an object around an axis like the stripes on a barber's pole (see Figure 3.34). Twist may be affected by coordinates, axes constraints, and the pivot point. Twist makes heavy demands on the affected faces of the object, so setting the proper mesh resolution is important.

FIGURE 3.34 Twist winds an object around the selected axis. It requires an object with substantial mesh resolution along the twist axis, or the results may be disappointing.

### Squash and Stretch

The transforms Squash and Stretch are modified scale operations that treat the object as though it has liquid inside it. Instead of merely expanding or collapsing an object to any degree you select, they make it act as if it were made of bubble gum. Squashing the object makes it spread out around the edges, and stretching makes the object get thin in the middle (see Figure 3.35). Squash and Stretch may be affected by coordinate settings, axes constraints, and the pivot point.

FIGURE 3.35 Squash and stretch in action: (a) The base object. (b) Squash makes the object spread out around the edges. (c) Stretch makes the object thinner in the middle, as if you were pulling gum apart.

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