This page provides information on the Frame Info rollout.
The Frame Info roll-out allows you to quickly check the size, dimensions, and contents of the loaded cache file for the current frame. The information is for display only, and cannot be changed on this roll-out. To change the input file, use the Preview & Render Cache Path field on the Input roll-out.
Container Dimensions - if a file is successfully loaded, shows the size of the bounding box of the cached contents for the current frame, in scene units. Prints [No Frame Loaded] otherwise. This parameter ignores any transformations (such as Scaling) applied to the transform node.
Cache File Content - if a file is successfully loaded, displays information regarding the channels present in the cache for the current frame. The container's size, as well as the total number of cells/voxels, is printed at the top. For each individual channel (such as Velocity, or Smoke), a single line consisting of the name and Min / Max range for that channel is also displayed.
The Info Box will only display channels which are remapped to the internal VolumeGrid channels using the 3rd Party Channels Mapping dialog in the Input roll-out.
For example, if your cache files contain a channel called my_test_channel which you intend to use as Smoke, forgetting to remap my_test_channel to Smoke in the Input tab will result in my_test_channel not being shown in the Info Box.
This is intentional, and the reason is optimization - loading and calculating the range of a channel can be time-consuming, especially with large datasets. If the channel is not used (ie. remapped to something), it won't be considered by the Cache File Content window.