Take a look at the sign below - changing the sign text to read something different would be a difficult task using traditional methods. But it is much easier when using Vanishing Point.
The Vanishing Point tool is a great feature in helping you to work within an image that has elements in a specific perspective, without having to jump into the entire 3D package in Photoshop.
To begin, activate Vanishing Point by clicking Filter > Vanishing Point. A giant dialog box appears. Now create a plane that simulates the perspective of the sign by activating the Create Plane tool.
Click to drop a point in each corner of the sign. A blue grid pattern should appear over the sign showing you the lines present in the perspective. Then click OK.
NOTE: If your grid boundaries are red and there is no grid pattern, this means the shape you created cannot be a true perspective. If that happens, adjust the corner points until it becomes a blue grid.
Open up your design that you will use to replace the sign.
If you are working in a layered document, press CTRL+ALT+SHIFT+E (PC) or Cmd+Option+Shift+E (Mac) to create a new layer that combines all the visible layers. Select all, and then press CTRL+C or Cmd+C to copy the selection to the clipboard.
Go back to the sign image, and reopen the Vanishing Point dialog box. You will find that the perspective grid created earlier is still there. Press CTRL+V or Cmd+V to paste the new sign graphic into this dialog box. At first glance, it will look like it didn't work. See below.
Simply drag the pasted layer to the perspective grid and it will automatically snap into the correct perspective. You may need to press CTRL+T or Cmd+T to transform the pasted layer larger or smaller to better fit the window.
NOTE: Drag the pasted layer around in the perspective window until you find the edge, then grab the corner or edge handle to scale.
Another great feature of Vanishing Point: when working along a perspective, it can be difficult to remove an object from the image. Here is an example of removing a manhole cover using the Clone Stamp tool inside of Vanishing Point.
Open Vanishing Point. Start by laying out a perspective grid, using the road lines as a guide. Since you will only be able to use the Clone Stamp Tool inside the grid that was drawn, the grid has to be widened to cover your entire working area. Simply click and drag the handle that is in the center of the edge. The grid will expand, keeping the correct perspective.
The Clone Stamp Tool inside of the Vanishing Point looks and works the same as the Clone Stamp tool on the standard toolbar. Simply ALT or Option click to select the sample point, then paint where the corrections are necessary. The Clone Stamp Tool gives you a nice preview before you stamp, and it will adjust along the perspective as you move, allowing for easier editing.