Boolean Operations

Boolean Operations in Bryce are named after George Boole (1815 - 1864) who invented a system of algebra upon which they are based. Although the title sounds strange, there is nothing particularly complicated about it.

The operations consist of applying one of three attributes to different Bryce primitives which are then grouped together to cause the Boolean effect to become visible. The three attributes are Positive, Negative and Intersect. They are enabled by clicking on the [A] button and checking the appropriate attribute.

You will complete the four assignments on this page:

Name each assignment as instructed and turn in the .br5 and .bmp files for each one.

Create 3 Boolean Objects

Here are two objects, a sphere and a cube, centered on each other.

The cube has been given a Positive attribute and the sphere a Negative attribute.

Both are selected and are about to be grouped by clicking on the [G] button.

Make this object

In these and following images the Positive object is Green and the Negative object is Red.

On the left are the two objects before grouping and on the right the objects after grouping. As you can see the space occupied by the negative object has been cut out or subtracted from the positive object.

Make this object.

OR

Select the previous group, Control + D to duplicate. Ungroup the objects, change the colors and switch the positive or negative settings in the Attributes)

Here the cube is now negative and the sphere is positive and the images show the result before and after grouping.

Whenever you use an object with a Negative attribute you also have the option of checking the Transfer Material of Negative Boolean. With this checked, the Red from the negative shows on the cut surfaces of the positive. If it was unchecked the result would be all green.

If one of the objects is given a Positive attribute and the other an Intersect attribute (it doesn't matter which, the result is the same) you get the effect shown to the left when they are grouped.

Only the space which is common to both objects is rendered.

Make this object; save the file with all three Boolean objects in it as lastname_boolean

That is all there is to it.

It should be noted that the objects used can be single objects or grouped objects.

When using groups it is important to make sure each of the objects in the group have a positive or negative attribute and that the group itself is also given a positive or negative attribute before further boolean operations are carried out.

Arched Opening in a Wall

Here a Positive cylinder is placed on top of a Positive stretched cube and both are grouped together. The group is given a Negative attribute.

The wall is another stretched cube with a Positive attribute.

Make sure the wall is narrower (less thick) than the Negative group. The arched group should protrude on either side of the wall.

Make this object

The image on the left shows the two objects before grouping the wall and the door group; the one on the right shows the result of grouping the two together. This could also be achieved by setting the cylinder and first cube both to negative and grouping the three individual objects together.

Notice that the inside surface of the arch has the color of the door group; this means the Transfer Material of Negative Boolean attribute was checked.

Bowl

Here a Positive sphere has a smaller Negative sphere centered inside it and both of them are grouped together. The group itself is made Positive.

A negative cube cuts off the top to form the rim.

Below left shows the arrangement before grouping and below right after grouping.