| iTool User's Guide: Working with Volumes |

## Extracting an IsoSurface

An isosurface is a set of polygons drawn in the volume to represent a surface that has a specific constant value (the isovalue). An isosurface cannot be translated, scaled, or rotated relative to the volume but does move with the volume.

To create an isosurface, select Operations Volume Isosurface and iVolume displays a dialog allowing you to specify the isovalue. If the volume is multi channel, you can select a channel and set its isovalue.

Figure 14-6: Isosurface Value Selector for iVolume

Figure 14-6: Isosurface Value Selector for iVolume

You will then create an isosurface for that channel by selecting OK.

Figure 14-7: Isosurfaced Rendered Volume

Figure 14-7: Isosurfaced Rendered Volume

Note Isosurfaces often contain a large number of polygons, which may degrade iVolume's display performance. When selecting the isovalue, you can also specify a decimation percentage to reduce the number of polygons in the resulting isosurface. This decimation step requires additional time, but the resulting isosurface will contain fewer triangles and will draw faster.

Consider adding a light to improve the isosurface display. Select Insert Light to add a light.

IDL Online Help (March 01, 2006)