The Files form is used to load a file from disk into a new or existing VMD molecule. It can be brought up by choosing New Molecule... from the File menu, or by hilighting a molecule in the Main form and choosing the Load Data Into Molecule... menu item. Once the form appears, select the file you want by using the file browser or by typing the filename into the text entry area. By default VMD will try to guess the type of file you are loading by matching the filename extension with one of the file reader plugins in the file type list (the available file types are described in Chapter 3). If VMD is unable to guess the appropriate file type or guesses incorrectly, you must select it from the list manually.
You can control into which VMD molecule you want to load your data by selecting it from the Load files for: popup menu at the top of the form. If the file being loaded is intended for a new molecule, select New Molecule instead. If the file being loaded contains additional coordinate frames, electron density map, or other ancillary data for an existing molecule, choose the appropriate molecule from the selection list at the top of the form. If the file being loaded contains trajectory frames , you have the option of loading a subset of the trajectory skipping ranges or strides of frames rather than the whole thing. You can also select for VMD to load all frames before continuing on, or to load them in the background so that you may continue to interact with the menus and forms while it loads additional frames . If the file being loaded contains multiple volumetric data, you may select which data sets you would like to load.
Once you have selected the file to be loaded, the appropriate file type, and the way it will be loaded, press the Load button and VMD will being loading the selected file. Any informational messages, errors or warnings which occur while loading the file will appear in the text window.
By default, VMD will load all of the frames contained in a coordinate or trajectory file.
Sometimes you may not want to read in a whole coordinate or trajectory file. For example, you may only want the last frame, or every tenth frame. You can do this by changing the options in the Frames control of Files form. The Frames controls consist of three numeric input fields labeled First, Last, and Stride. These make it possible to use a subset of the frames, starting at frame First and selecting every Stride frames until the Last is reached. For instance, to select every fifth frame between frames 14 and 98, set:
(Remember that frame numbers in VMD start at 0, so frame 0 is the first frame.) The value `-1' is a special number; setting First to -1 is the same as starting at the first frame, Last = -1 is the same as ending at the last frame, and Stride = -1 is the same as taking one step.