1. From Protocol Editor tab, click Add New Class 
.
A new graph appears with no points on it, indicating zero opacity. The image appears totally black.
2. Type the name of the new class.
3. Click above the line of opacity to determine the level of opacity required for the image.
A point appears on the graph.
4. To adjust the level of opacity, drag the point higher or lower.
The level of opacity depends on what you want to view in the image. You can add several points to attain the required level of opacity.
To change the level of opacity of the whole class, slide the Line of Opacity slider left or right.
The number beneath the line of opacity indicates the percentage opacity.
5. To show the class in the volume rendered image, select the Active check box.
To hide the class (deactivate), deselect the Active check box.
6. To allow windowing, select the Allow Windowing check box.
As the colors in the 3D image change, the colors in the graph change.