Maya Boolean Modeling

May 24, 2017

Maya Boolean Modeling

Learn how to do Boolean modeling in Maya. From basic boolean operations, anatomy of a boolean, where to use Booleans to common Boolean errors, you will surely learn the basics here. In order to follow this tutorial, it’s best if you have a basic knowledge of Maya.

But before we start, let’s understand what Booleans are. Well, Booleans in Maya is only possible between two objects, with the first one to be booleaned and the other to be added. Boolean allows you to subtract, add or intersect one object’s geometry to another.

Common 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. Booleans are prone to errors.
  3. Due to the geometry that it produces, smoothing a booleaned object can become a pain.

Setting Up the Project

Set the menu to polygons. Create two spheres, and move them so they intersect like in the image below.
two-spheres-boolean
Select both spheres then go to mesh>booleans..
boolean-operations
Note: There are 3 different boolean operations:

  1. Union – This will merge both objects together. It will get rid of geometry between the two pieces.
  2. Difference – Subtracts the last selected geometry from the first selected geometry.
  3. Intersection – The geometry between the two objects will be kept and the rest will be removed.

boolean-operations-2

Anatomy of a Boolean

Note: You can skip this section if you’re a beginner and don’t particularly care about this.

  1. Go back to set-up and create the two spheres again.
  2. Select them both and go to mesh>boolean>difference.

**It may appear like the other geometry has been removed and has only left the protruding surface in the boolean sphere. But in reality, the geometry hasn’t been deleted. Its vertice and transformation information is still there.

How to access it?

  1. Go to window>outliner.
  2. There will be two groups: pshpere1, pshpere2, and the outputted geometry. Maximize the groups so you can see inside of them. Each one has a transform node.
    anatomy-boolean
  3. Select the group pshepre2 and you will find that, when using the move tool, you can move the sphere’s geometry around, therefore watching the boolean in real time.

How boolean works:

It takes both geometry’s shape nodes, connects their outputs to a boolean node, then the boolean node generates a new mesh(based on the outputted information from the geometry shape node).

To see this connection, select the visible boolean output geometry and go to window>hypergraph: connections.
As you can see, the “out mesh” and the “worldmatrix” of both sphere’s shape nodes have been connected to a boolean node and the boolean node outputs the new geometry.

anatomy-boolean-2
Note: If you want to animate your Booleans, simply set key frames on the boolean geometry groups.

Where to Use Booleans

As mentioned earlier, 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.

  1. Step one – Download example file here.
  2. The red sphere has been assigned a blinn with its color set to red. The blue sphere has been assigned to a lambert with its color set to blue.where-to-use-booleans
  3. Select the blue and then the red sphere, and go to boolean>difference.where-to-use-booleans-2

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

Common Boolean Errors

Boolean is probably the fidgetiest function in Maya.

Inverted boolean operations

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

How to Fix It- 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

Cause – Scene tolerance.

How to Fix It

  • Select both objects and group them. Scale the group until it’s noticeably larger than the grid.
    common-boolean-errors
  • Then do the booleans and after that select the boolean geometry and then the group, and go to edit>parent.
  • Next, go to edit>delete all by type>history
  • Then 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.

Note: If you want to test this out for yourself, download badgeo.mb.

Cause – Modeling history and history of previous booleans.

How to Fix It

  1. 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 can’t boolean more than two objects at once.
  • You can’t boolean different types of geometry. Example: you can’t boolean a polygon with a NURB.
  • It’s a good practice to delete history after you finish with the boolean because this can cause problems.
  • Don’t accidentally delete history if you’re animating a boolean.

That’s it and Goodluck with your project. Let us know how it goes.

Leave a Comment

Previous post:

Next post: