Why does the result of my Volume Combine process look different to my group of the same volumes?
The group will use the settings of the individual volumes to adjust the displayed amplitudes. In a group, the volumes might have different amplitude ranges, but still display similarly.
Volume combine doesn't "see" the display settings, only the actual trace values. After combining, the resulting volume will contain the unchanged amplitudes from the original volumes.
The solution is to apply a scale to the volumes before combining. There are two easy ways to do this:
- Use a Volume Maths (Simple) process to apply a scale, and combine the resulting volume; or
- Use manual mistie correction to adjust the scale of the volume as it is read.
Adjusting amplitude scale of two volume groups
A timeslice view of both volume 1 and volume 2 grouped together. However, volume 2 has twice the amplitude range of volume 1, making the amplitudes display more intensity.
To adjust the colorbar range so that they have the same scale relative to amplitude values for each volume:
- Uncheck the ‘Use min and max from class settings’ box
- Adjust the the Min/Max values for volume 2 to correlate with those in volume 1.
- The colourbar range for each volume is scaled to amplitude values (of one volume) so that amplitudes is shown with the same intensity across both volumes.
Create a combined volume with the same amplitude value range
- Go to Process tab and add a Volume Maths (Simple) process.
- We will use Volume Maths (Simple) to rescale volume 2 to volume 1. Since volume 2 has twice the amplitude range of volume 1, dividing the values by two will properly scale volume 2.
- Still in the Process tab, add a Volume Combine process.
- Using the Volume Combine process, select volume 1 and the rescaled version of volume 2 (created from Volume Maths (Simple) process earlier) as the Input Volumes. This will create a new volume combining volume 1 and volume 2, with both having the same amplitude scaling.
Manually adjust the amplitude scale.
The amplitude scale can also be adjusted manually from the Configure Volume window.
- To scale the amplitude of Volume 2 to Volume 1, enter ‘0.5’ as the input for ‘Amplitude Scale’.