Up in the Loft: Creating and Editing Lofted Objects






Up in the Loft: Creating and Editing Lofted Objects

Creating 3D models by lofting is an essential modeling option for 3D artists and animators, and 3ds max has some of the finest lofting controls around.

The lofting process requires that you have two 2D shapes placed in a scene. One of the 2D shapes acts as a path; the other 2D shape is defined as a cross-section. The cross-section is basically pulled along the path to form a 3D object or model. If you can’t quite visualize this action, perhaps this analogy helps. Suppose that someone asked you to model a sausage (it could be a tofu sausage for all you non-meat-eaters). A sausage is sort of like a cylinder, except it usually has a slight curve along its length. A cross-section of the sausage, literally a slice at some point along its length, is a circle. A curved line segment — the path — could represent the whole length of the sausage. If you had a method of pulling the circular cross-section along a slightly curved Path, a 3D sausage model would be the result. Here are a few different loft ideas for you to explore. Each uses different paths and cross-sections.

Lofty ideas

A penta-tube is my term for a 3D form that is tubular with five equidistant bends, like a garden hose that bends back on itself. Here’s how to create a penta-tube loft. Follow these steps:

  1. Choose Create>Shapes>NGon, and create a pentagon in the Top Viewport.

  2. While Create>Shapes is still in effect, choose Circle and create a circular 2D shape.

    Make the pentagon about 1/12 the scale of the Circular 2D shape, as shown in Figure.

    Click To expand
    Figure: Your Front Viewport should look like this, containing both a circle and pentagon.

  3. Choose Create>Geometry>Compound Objects.

  4. Choose the Circle and click Loft.

  5. Click Get Shape in the Loft Command Panel, and then click the pentagon in the Top Viewport.

    You have generated a lofted object, as shown in Figure.

    Click To expand
    Figure: The Pentagon has acted like a cross-section, and the Circle like a Path, to create this lofted 3D model.

To explore another loft operation, return to the screen that shows just the two 2D shapes: choose Edit>Undo twice. Here’s the second operation:

  1. Select the pentagon.

  2. Choose Create>Geometry>Compound Objects>Loft.

  3. Click the Get Shape button.

  4. Click the circle in any viewport.

    The pentagon acts as your path, with the circle as the cross-section. This creates a different lofted 3D model than before, as Figure shows.

    Click To expand
    Figure: The lofted model created here looks like a pentagonal pillow.

The path shape doesn’t have to be a closed shape. Follow these steps to get an open shape:

  1. Choose Create>Shapes.

  2. Create a curvy line and a circle in the Top Viewport.

  3. Select the curvy line shape, and then choose Create>Geometry> Compound Objects>Loft.

  4. Using the Get Shape process, select the circle as the shape.

    Figures 6-13 and 6-14 show the results.

    Click To expand
    Figure: Here is the 2D shape you started with.

    Click To expand
    Figure: This is a result of lofting the circular cross-section to the curvy path. Is it a discarded hose? A hastily squeezed volume of toothpaste?

One of the coolest 2D shapes to use as a loft path is the hydra — a coiled path through 3D space. Figure shows a 2D star shape as a cross-section for a hydra path in a lofting operation.

Click To expand
Figure: A star shape lofted to a hydra path.

Tweaking the cross-sections

As you have probably noticed from the lofting operations in this chapter, the 3ds max Loft operation pays little attention to the relative sizes of cross-section and path. You can, however, edit the size of the cross-section. If you plan to create a lot of lofted objects, you’re in luck: You can edit them all from within the Loft Command Panel.

Basic changes in scale

If you want to change the size of a lofted object, here’s the drill:

  1. Create some lofted scene content.

    For this example, create a random curved path — and then loft a circular cross-section to it, as shown in Figure.

    The model in Figure looks bloated, as if it soaked in water too long. To get an object that looks more like a rope, follow the next few steps.

  2. Click the lofted object selected in a viewport to select it.

  3. Choose the Loft options in the Modify Command Panel — in particular, Deformations.

    The Deformation controls open.

    Click To expand
    Figure: This lofted object is the result of lofting a circular, 2D, shaped cross-section to a randomly curved 2D path.

  4. To edit the size of the cross-sections that contribute to the lofted object, click Scale.

    The Scale Deformation Panel appears, as shown in Figure.

    Click To expand
    Figure: The Scale Deformation Panel in the Loft Command Panel options.

    The Scale Deformation Panel gives you some choices to make:

    • Scaling down to zero: A bold horizontal line at the zero point represents a scale of zero (in effect, an object too small to see). Values above the zero point increase the size of a cross-section; values below the zero point shrink the cross-section.

    • Scaling up to 100%: Above the graph, a crosshair icon is selected by default; a red line shows at the 100% point. At each end of the red line is a black circular control point. Placing your mouse pointer over either dot enables you to move this control point up or down — toward or away from a scale of 100% (which is, in effect, a “full-size” object).

    • Choosing your starting and ending points for the path: The dot at the left represents the size of the cross-section at the start of its path; the dot on the right represents the size of the cross-section of the lofted object at the end of its path.

  5. Click and drag both control points to a value of about 20 on the graph.

  6. Close the Scale Deformation Panel.

    You can now see the lofted object in any viewport.

Changing the scale for specific parts of an object

If you scale the starting point small and the end point large, you get the object shown in Figure.

Click To expand
Figure: Here’s the result of a small-scale value for the cross-section’s start point, and a large value for the end point. This could be the start of a 3D model of a snake.

But if you want to get fancy with the process of deforming objects, how about altering the cross-section sizes at several points along the length of the path? Can you do that? Yep. Click and hold down the mouse button over the Scale Deformation menu; then select an icon from the list that appears. The Insert Corner Point icon creates sharp corner points whereas the Insert Bezier Point icon adds smooth curves to the scaling path. For now, select the Insert Bezier Point icon.

When one of these control icons is active, you can click the scaling line to add a curve point. Add as many as you like. After they’re added, you can move them up and down to adjust the scale of the cross-section at that point on the path, as shown in Figures 6-19 and 6-20.

Click To expand
Figure: Top: The Scale Deformation curve after several curve points are added and moved. Bottom: The resulting cross-section scaled object (T. Rex intestines? Yuck!).
Click To expand
Figure: Using the Loft Scale Deformation process, you can create an infinitely varied number of You can tweak the other values in the Command Panel to see what you get.

In addition to the Scale option in the Deformations options of the Loft Command Panel, another four items are available: Twist, Teeter, Bevel, and Fit. With a bit of practice, you’ll have little trouble customizing lofted objects with these deformations as well.

Although you access lofting by choosing Create>Geometry>Compound Objects, it could just as well be considered a way of modifying an object — especially when you’re using the Deformation options. That’s right handy for this book — because the next chapter gets into 3ds max modification options.



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