This tutorial will cover in depth, basic boolean operations where to use booleans, and common boolean errors (example: objects disappearing, inverted operations).

SET-UP

It’s best if you have a basic knowledge of Maya 2016 to follow this tutorial

Set the menu set to polygons.

Create two cubes, and move them so they intersect like in the image below.

WHAT IS A BOONLEAN

Booleans in Maya will let you take an object, subtract, add or intersect its geometry onto another object (merging). A boolean can only happen between two objects. The first selected object will be booleaned. The other piece will be added.

Booleans are great, but have some drawbacks.

1. The geometry is less than savory, but still usable, and can be re-worked with a little time. Edge loops will be hard to keep.

2. Prone to errors.

3. Due to the geometry that it produces, smoothing a booleaned object can be difficult. 

Let’s get started.

BOOLEAN OPERATIONS

Step one – Select both cubes and go to mesh>booleans…

There are 3 different boolean operations:

Union – This will merge both objects together. It will get rid of geometry between the two pieces.

Difference – Subtracts the last selected geometry from the first selected geometry.

Intersection – The geometry between the two objects will be kept and the rest will be removed.

WHERE TO USE BOOLEANS

As mentioned before, booleans do have drawbacks. So the rule of thumb is if you need to smooth the surface later, example: organic modeling – people – animals, you probably don’t want to use boolean. If it’s a surface like a monitor, computer or keyboard, booleans are great.

 Booleans and shaders. 

When you boolean an object, shader information is also booleaned.

The red cube has been assigned a blinn with its color set to red. The blue cube has been assigned to a lambert with its color set to blue.

Select the blue and then the red cube, and go to boolean>difference.

As you can see, the shaders are also boolean, so all the faces that the red cube intersected are red, and the rest are blue.

COMMON BOOLEAN ERRORS



- Inverted boolean operations



#1 Cause – Inverted normals. One of the surface’s normals is probably facing backwards.



Fix – Select one of the objects and go to normals>vertex normal edit tool. This will show the normals as lines coming off the vertices. If you don’t see any lines facing outwards, go to normals>reverse. If you don’t see any reversed normals, select the other object and reverse its normals, and that should fix it.

– Objects disappearing



# 1 Cause – Scene tolerance.



Fix – Select both objects and group them. Scale the group until it’s noticeably larger than the grid.

Then do the booleans and after that select the boolean geometry and then the group, and go to edit>parent. Now go to edit>delete all by type>history, and select the group and, in the attributes editor, set the scale properties back to 1 and it will resize the geometry back to its original size.

#2 Cause – Modeling history and history of previous booleans.



Fix – Go to edit>delete all by type>history.

ADDITIONAL INFORMATION

– Make sure both pieces of geometry are of similar geometry density.

– Never boolean on only one face.

– You cannot boolean more than two objects at once.

- You cannot boolean different types of geometry. Example: A polygon with a NURB cannot be boolean.

– It’s a good practice to delete history after you finish with the Boolean.

– Don’t accidently delete history if you’re animating a boolean.