1. In the Control Panel, open the Class tab.
2. In the tree, select a class to open the Details Panel.
3. In the Details Panel, adjust the Opacity slider or enter the opacity value (0 = fully transparent, 100 = fully opaque).
   • Moving the slider to the left side makes the object fully transparent, the right fully opaque.

The most common use of variable-opacity is to co-render multiple volumes. This example shows a group with two volumes: a semi-transparent velocity model on top of a seismic volume.

See Creating a Group for more details on grouping volumes.

When changing the colour of any line, item or annotation in Insight, you can also adjust the opacity of that object.

1. Click on the colourbar that defines the colour of the object.
2. Click on the arrow at the bottom of the pre-defined colours to open the Select Colour window.
3. Adjust the opacity slider on the right of the window. Moving the slider down makes the object fully transparent, and moving it up makes it fully opaque.