First, knowing that I didn't want the Liquify filter to affect anything in the image except the dogs, I placed a selection around them that ended at the leash. I had no intention of modifying anything below the leash, either. When you then choose FilterLiquify, the Liquify dialog opens. As you can see from Figure 10-15, the Liquify dialog is another one of Photoshops applications within an application.
Figure 10-15. The Liquify dialog after selecting the dogs. I have already come pretty close to the final effect using nothing more than the Bloat and Push tools.
NOTE
At the bottom of the dialog is a checkbox called Show Backdrop. Check it if you want to see layers in the same image. You can choose All Layers or a specific layer and whether you want the other layer to appear in front or behind the Liquify layer. If you use a knockout, you can display the originating layer beneath the Liquify preview. That way, you can tell how well your distortions of the knockout will fit into the background. You can also tell whether or not you need to clone background into the part of the image that the knockout was "lifted" from.
You could use a grid over the image to help you visualize how much and where you've distorted the original. The grid is called the Mesh. To use it, just check the Show Mask box. You can choose the Mesh's color and size from menus.
When the dialog opens, the red color designates the area masked by the selection. You could paint a mask around the edge with the Freeze tool or erase it with the Thaw tool. Both are just above the Hand tool in the Toolbox. Masking protects areas from being distorted by the other Liquify tools so that you don't smear parts of the image unintentionally.