The Tips in detail

 "Compound Objects disappear"

After performing a boolean operation to create a Compund Object, the object may not render or even disappear from the screen. Look at the "Display" settings of the Boolean command. The default setting for "Display" is "Result". If this setting automatically switches to "Operands", you have performed an invalid Boolean operation. The Operands will be visible in the viewport but they will not render. Switching back to Result will cause the Boolean Object to disappear. If an Intersection operation were attempted on two objects that did not intersect, the result would be as described above.

Creases or ridges may be caused by a Boolean operation between an object that has very few faces and an object that has considerably more faces (for example, subtracting a complex free form object from a box).

3D Studio MAX and VIZ will try to tessellate the surface of the box so there are additional faces for the subtraction. Unfortunately, the faces are usually generated as long, slivered faces that sometimes overlap and form creases or ridges in the rendered scene. Increasing the Segment parameters of simpler objects will make them less likely to display creases or ridges.

The application of some modifiers may cause this phenomenon (for example, an Optimize Modifier with a high Face Thresh). To avoid this, use a higher Bias setting, such as 0.3. Also, if an object has been tessellated at a face, Sub-Object level, long faces may also result.

Lofted objects can also end up with long, thin faces if their Path Step setting is set to a low value. In these cases, the Edit Mesh modifier has an Edge/Divide command that might help reduce the long faces.

Performing consecutive Boolean operations on multiple objects, some components may disappear.

To reproduce this phenomenon, create a Sphere that is intersected by two Cylinders. Union (join) the cylinders to the sphere. With the sphere selected, you click the ‘Pick Operand B’ button and select one of the cylinders. It will turn the same color as the sphere so the Boolean operation was successful. Then, click the ‘Pick Operand B’ button again, and choose the other cylinder. The first cylinder disappears.

There are two methods for performing this process without having components disappear. One method is to exit the Boolean command after each Boolean operation. The second method is to attach all the ‘operand B’ objects.

When performing multiple Boolean operations, check each result carefully for stray faces and fix them manually before attempting the next Boolean operation or the final smoothing operation. You may have to delete or rebuild some faces.

Performing Boolean operations on splines made in the Create/Shapes menu can be confusing. Before performing the operation, make sure all the shapes you plan to work with are attached. Shapes do not intersect, subtract, or union unless they are attached.

If you know you have to perform a Boolean operation on shapes you are drawing, make sure to deselect the ‘Start New Shape’ button before drawing your shapes. This will ensure that all the splines you create are part of a single shape.

If a set of operands never seems to produce desired results, try adding a modifier and collapsing the stack to create an Editable Mesh. In both 3D Studio MAX and 3D Studio VIZ R2.x, you can collapse objects to editable meshes without first applying modifiers. If you do this, you will no longer be able to adjust the parameters of the existing modifiers on the stack.

If you notice that the Boolean Object is not as smooth as you would expect, try deselecting the Optimize Result option in the Update portion of the Boolean menu. 3D Studio MAX will automatically calculate the result again and smooth the edge.

In general, create objects that have more faces than you might normally use. For instance, increase the Height, Width, and Length segments of a Box, especially if the other object is more complex. Try to make the face count of both operands similar in number. With a larger number of faces, the edge created by the Boolean operation will tend to be smoother and more refined because there is less of a chance that long, thin faces will be introduced. Once the Boolean operation gives you the results you want, apply the Optimize modifier to reduce the number of faces on the object. If further face editing needs to be done, deselect Backface Cull and Edges Only from the Display tab. The faces on the object will show up better.

If a Boolean operation continually fails, try exporting the operands to .DXF or .DWG format. Import the objects and try the Boolean operation again. Sometimes slightly moving or rotating one of the Operands will allow the operation to work properly. You also might have success if you choose the operands in a different order.

One way to check the validity of objects that you intend to use as operands is by applying the STL-Check modifier. This modifier is primarily used to verify that an object is a complete and closed surface in preparation for exporting to .STL file for CNC machines. Because Boolean operations work best with objects that meet the same criteria, use STL-Check on your operands. STL -Check is located under the More... button in the Modifier tab. After applying the STL-Check to an object, activate the checkbox next to Check. The Status section of the menu will tell you if errors are present.

Boolean operations can fail if the operand is an open object. For instance, if you have a Cylinder with its top removed, or an extruded Spline with no cap, cap the objects or try building new faces over the open area.

Objects that are created with Lathe, and some extruded objects, can make invalid operands. For example, if you create an Ellipse, then assign a Lathe modifier to generate an oval-shaped object.

The Hedra object is not a valid operand. Any Boolean operation that you attempt with a Hedra will fail.

You might notice that the Boolean Object does not correctly render at the seams. The surface may appear streaked, stretched or creased. This can be caused by unwelded vertices, which will cause very tiny or long, sliver-like faces. Zoom in and apply an Edit Mesh modifier to the operand so you can weld vertices together.

Also refer to: "Compound-objects don't work."