One of the more robust of the distortion filters is the Liquify filter, which you were introduced to briefly back in Chapter 20. There you saw how the Liquify filter could be used to distort pixels, creating flames; now we'll take a step back and examine how the filter works more closely.
Liquify is one of the few stand-alone filters in the Filters menu, appearing alongside Vanishing Point (covered in the next section of this chapter) outside of any of the filter categories. It was added to Photoshop back in version 6, and has since proved to be a highly useful part of any digital artist's toolset. It works by overlaying a mesh or grid over your image, and associating the pixels in your image with points on the grid. When you're distorting the image, you're really moving the grid points around, and the corresponding pixels in the image follow.
The Liquify tool's dialog box, which you can access by choosing FilterLiquify, is shown in Figure 21.1. As is the case with most of the other filter dialog boxes, you can change the zoom level and move around the preview area using the provided controls. On the left side of the dialog box, you'll find an array of tools used to apply the distortion, and on the right are numerous settings used to modify the Liquify tools.