1. Create a new Volume Maths process from the control panel
2. Name the process: “Zone highlights”
3. Add your two input horizons.
4. Use the default horizon variables ‘h1’ and ‘h2’
5. Use this formula: if (twt_ms < h1, 1, if (twt_ms < h2, 2, 3))
   • twt_ms is contains the two way time value
   • h1 and h2 are horizon times
   • This formula reads as:
     • If the time value is less than “horizon 1”, output value “1”, OTHERWISE
     • If the time value is less than “horizon 2”, output value “2”, OTHERWISE
     • Output value is “3”
6. Choose the output survey.
7. By default, this process creates a volume with the class set to “unknown”. To get a great looking display, we’ll need to update the class.
8. In the Class tab of the Control Panel, Create a new class.
9. Name the class “Zone Indicator”.
10. Load a nice colourbar (hint: banded colourbars work really well for indicator volumes).
11. Set the min and max values to the first and last output values from the volume math, i.e. 1 and 3.
12. Finally, in the Volume tab of the Control Panel, choose the “Zone Highlights” result volume, and set the class to “Zone Indicator”.

You can incorporate more horizons and layers by adding more nested “if” statements or by linking multiple Volume Maths processes.

In this example, I’ve created a Zone Indicator class using the editing tools. It has three abrupt boundaries.  To use the indicator class in other projects, Export it to disk (In Control Panel, Right Click and choose Export)