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Figure 17-17: Using the Scatter object, we can add trees to our island terrain.

Creating Connect Objects

A Connect object is useful for building a connecting bridge between two separate objects. Each object must have an open face or hole that specifies where the two objects are to be connected.

To use this object, delete a face on two Editable Mesh objects and then position the holes across from each other. Select one of the objects and choose Create Compound Connect menu command. Then, click the Pick Operand button, and select the second object. The Connect object builds the additional faces required to connect the two holes.

Filling object holes

If multiple holes exist between the objects, the Connect object attempts to patch them all. You can also use the button several times to connect a single object to multiple objects.

Caution

The Connect object doesn’t work well with NURBS objects.

Figure 17-18 shows a normal Connect object without any smoothing options.

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Figure 17-18: Two cylinders connected using the Connect object

The Parameters rollout includes a list of all the operands or objects involved in the connection. You can delete any of these with the Delete Operand button. The Extract Operand button lets you separate the Operand object from the Connect object.

In the Interpolation section, the Segments value is the number of segments used to create the bridge section, and the Tension value is the amount of curvature to use in an attempt to smooth the connected bridge.

The Bridge Smoothing option smoothes the faces of the bridge, and the Ends option smoothes where the bridge and the original objects connect.

Tutorial: Creating a park bench

The Connect object is best used between two symmetrical copies of an object that need to be attached, as with a table or bridge. For this tutorial, we use the Connect object to create a park bench between two end pieces.

To connect two ends of a park bench, follow these steps:

1.Open the Park bench.max file from the Chap 17 directory on the CD-ROM.

This file includes symmetrical ends of the park bench. One end was created by extruding a spline shape and using the ShapeMerge tool to cut matching holes on the inner facing surfaces. The Mirror tool was then used to create and rotate the symmetrical clone.

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2.Select one end of the park bench, and select the Create Compound Connect menu command.

3.In the Pick Operand rollout, click the Pick Operand button, select the Move option, and click on the opposite side of the park bench.

The two end pieces connect.

4.In the Parameters rollout, select the Smoothing: Bridge option to smooth the seat of the bench.

Figure 17-19 shows the resulting park bench.

Figure 17-19: A Connect compound object can join two open holes in separate objects.

Modeling with Boolean Objects

When two objects overlap, you can perform different Boolean operations on them to create a unique object. The Boolean operations include Union, Subtraction, Intersection, and Cut. The Union operation combines two objects into one. The Subtraction operation subtracts the overlapping portions of one object from another. The Intersection operation retains only the overlapping sections of two objects, and the Cut operation can cut an object like the Subtraction operator does, while letting the cut piece remain. Figure 17-20 shows each of the possible Boolean operators.

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Note Unlike many CAD packages that deal with solid objects, Max’s Booleans are applied to surfaces, so if the surfaces of the two objects don’t overlap, the Boolean operation has no effect.

Figure 17-20: Boolean operations: Union, Intersection, Subtraction (A-B), Subtraction (B-A), and Cut: Remove Inside

All Boolean operations are layered in the Stack. You can revisit an operation at any time and make changes to it.

Cross- You can also apply Boolean operations to shapes using the Boolean operators available for Reference Editable Meshes in the Geometry rollout. Chapter 13, “Drawing and Editing 2D Splines and

Shapes,” covers these 2D Boolean operators.

Union

The Union operation combines two objects into one. To Union two objects, select an object and click the Boolean button. Under the Parameters rollout, the selected object is referred to as Operand A. In the Pick Operand rollout, click the Pick Operand B button and select a second object in the viewport. (Operand B can be a Copy, Instance, Reference, or Move object.) To apply the Boolean operation, click the Union option.

Intersection

The Intersection operation creates an object from the overlapping sections of two objects. For this operation, like the Union operation, which object is A and which is B isn’t important.

Subtraction

The Subtraction operation subtracts the overlapping portions of one object from the other. For this operation, the order in which the objects are selected is important. Subtracting object A from object B gives you a different object from what you get when you subtract object B from object A.

Cut

The Cut operation is similar to the Slice modifier, except that it uses another object instead of a slice plane gizmo, and only Operand A is modified in the process. The Cut operation has several options, including Refine, Split, Remove Inside, and Remove Outside.

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The Refine option marks the selected object with new edges where it intersects Operand B. The Split option actually divides the mesh object into separate elements.

The Remove Inside and Remove Outside options are variations of the Split option. They remove the inner or outer portion of the object. These options work like the Subtraction and Intersection options, except that the Cut operation leaves holes in the base geometry.

Tips for working with Booleans

Working with Boolean objects can be difficult. If you try to perform a Boolean operation on an ill-suited object, the results could end up being erratic. As you prepare objects for Boolean operations, keep the following points in mind:

Avoid meshes with long, skinny polygon faces. All faces should have roughly equal lengths and widths. The ratio of edge length to width should be less than 4 to 1.

Avoid curved lines where possible. Curved lines have the potential of folding back on themselves, which causes problems. If you need to use a curve, try not to intersect it with another curve; keep the curvature to a minimum.

Unlink any objects not involved in the Boolean operation. Linked objects, even if they don’t intersect, can cause problems.

If you’re having difficulty getting a Boolean operation to work, try applying the XForm modifier (found in the Modifiers List) to combine all the transformations into one. Then collapse the Stack, and convert the objects to Editable Mesh objects. This technique removes any modifier dependencies.

Make sure that your objects are completely closed surfaces with no holes, overlapping faces, or unwelded vertices. You can check these criteria by applying the STL-Check modifier or by looking at all sides of the objects in a viewport with Smooth Shading enabled.

Make sure that all surface normals are consistent — inconsistent normals cause unexpected results. You can use the Normal modifier to unify and flip all normals on an object. The Show Normals option in the viewport can also help.

Collapsing the Stack after all Boolean operations have been performed eliminates dependencies on the previous object types.

Tutorial: Creating a Lincoln Log set

In the household where I grew up, we had sets of Legos and a lesser-known construction set known as Lincoln Logs that let you to create buildings using notched logs that fit together. Using a Subtraction operation, you can create your own virtual set of Lincoln Logs.

Cross-	This tutorial transforms objects and uses the Array dialog box. You can find information about
Reference	transforming objects in Chapter 10, “Transforming Objects — Translate, Rotate, and Scale.”

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To use Boolean objects to create a log cabin, follow these steps:

1.Open the Lincoln logs booleans.max from the Chap 17 directory on the CD-ROM. This file contains some simple primitives.

2.Select the Cylinder object, and choose the Create Compound Boolean menu command. In the Operation section, select the Subtraction (A–B) option. Then in the Pick Boolean rollout, click the Pick Operand B button and select one of the Box objects.

3.Repeat the Subtraction operation on the other three boxes by right clicking in the active viewport and performing Step 3 again.

When finished, you should have a cylinder with four notches.

Note	If you simply click the Pick Operand B button again, the first notch is replaced by the second
	operation.

4.Clone the single log by choosing Edit Clone and then selecting the Copy option. Move the cloned log along the negative Y axis a distance of 160. The easiest way to do so is to select the Select and Move button and right-click it to open the Move Transform TypeIn dialog box. In the Absolute World field, enter –160 as the Y-axis value.

This step positions two logs next to one another to form the bottom layer of the house.

5.Select both logs, and open the Array dialog box by choosing Tools Array. In the Incremental Move row, enter 10 for the Z axis. In the Incremental Rotate row, enter 90 for the Z axis. In the Array Dimensions section, enter a Count value of 16. Click the OK button.

This step stacks several layers of logs.

6.Select one log, and use the right-click pop-up menu to convert that log to an Editable Mesh. Open the Modify panel, click the Attach button, and then select every log to combine them all into a single object. Click the Attach button again to exit attach mode when you’re finished.

7.Select the Create Standard Primitives Box menu command, and create a Box object with the following dimensions: Length of 40, Width of 40, and Height of 80. Then position the Box in the Top viewport where the front door should be.

8.Return to the Compound Objects subcategory, select the logs, and click the Boolean button. Then click the Pick Operand B button again, and select the Box.

The rollout remembers and retains the last options selected, including the Subtract (A –B) operation.

9.To add a roof, select the Extended Primitives subcategory and click the Prism button. Drag in the Left view to create a prism object that covers the logs.

Figure 17-21 shows our Boolean log cabin, ready for the virtual pioneers.