Isosurface

The `Isosurface' representation computes and draws a surface within a volumetric data field, on a 3-D surface corresponding to points with a single scalar value.

There are several settings which control how the isosurface is displayed.

• Data Set - This control selects which volume dataset is used for the isosurface calculation, since a given molecule can contain multiple volumetric data sets.

• Isovalue - The Isovalue control selects the value for which the isosurface will be computed. In the GUI, when dragging the isovalue slider, the drawn isosurfaces are temporarily calculated at a lower resolution to improve interactivity; to prevent this behavior, you can use the middle or right button (or the control/shift/alt modifier keys) while dragging the slider.

• Draw - This can be set to Points, Shaded Points, Wireframe, or Solid Surface. The default drawing mode is Points. When viewing very dense isosurfaces of huge volumetric maps, the Shaded Points drawing method can be an excellent compromise between the speed of the Points method and the quality of the Solid Surface method.

• Boundary - Setting the boundary to Box causes the volume data bounding box and coordinate axes to be drawn rather than the isosurface for the data. This is often useful when first working with volumetric data, and checking that the coordinate systems of the volume data and the molecule match.

• Step - This setting can be used to greatly reduce the resolution of the generated isosurface, by skipping voxels.

• Size - This sets the thickness of the point and line based isosurface representations.

This and other volumetric display features will be greatly expanded in forthcoming releases of VMD.