Volume Rendering in VAPOR is controlled by the DVR tab, which stands for Direct Volume Rendering. Volume Rendering is used to visualize 3D variables as volume densities. The opacity and color are controlled by a transfer function. The transfer function can be used to make opaque the features of most interest, and color can be controlled to understand the data values in the regions of interest. The following is a typical use of volume rendering in observing turbulent flow:
The above screenshot is a volume rendering of the vertical component of momentum in a turbulent flow. The transfer function has been edited to highlight the strongest upward and downward momentum, and to make transparent the smaller values of vertical momentum. The colors have been mapped to make the negative momentum yellow to red, and the positive momentum blue to violet. A color bar is used to show the color map. Region mode is enabled, so that the current region of interest (where the volume rendering is occurring) is outlined with a red box.
Region extents define the volume to be rendered. For efficient volume rendering, the necessary data can be limited, by controlling the Region size, as well as by using LOD and Refinement level control.
