Wednesday, 6 January 2010

Distorting with Displacement Maps

The texture shows through really well using this Blend Mode overlay technique but you can take this further if you want. What we have here are two things: a textured overlay, as described, plus a significant image distortion. As you well know, digital pictures are rectilinear. EVERY picture is the same so sometimes it's nice to mess with that perfection, adding a distortion to a layer or, as was also the case here, to a rasterised text layer.

To do this I use Photoshop's filter (Filter>Distort>Displacement). This works on a selected image, applying certain elements from that file to the distortion. It's hard to explain how it physically works, but it can produce significant distortion on the selected area. Note I said "selected" area. If I just chose the workshop picture layer and applied the Filter>Distort>Displacement action, I'd add the distortion to the entire layer. If the level of distortion is big, it's going to seriously mess with both the edges AND the legibility of the subject. So, to control this:
- Make a quick, approximate selection inside the edges of your target picture (in this case it's the workshop).
- Feather your rectilinear selection by about 100 pixels so that the difference between what's distorted and what remains untouched is less obvious.
- Invert the selection so that your filter action affects the outer parts of the frame, not the inside.
- Apply the filter (Filter>Distort>Displacement). CS 'asks' for an image to work with. In this example it MUST be a Photoshop file, NOT a JPEG. So just point it to any .psd file lying around and see what happens. If it looks OK but is not quite enough, press Ctrl + F to repeat the last filter action - you get double the filter effect.
Press Ctrl + F again for still more displacement.

Tip: Once you've completed a few displacements, you might like to save specific .psd files for use in other displacement filter actions (like a special filter library to use whenever displacement maps are needed so you don't have to go hunting for a .psd file that works).
- You can also flip the .psd file 180 degrees to get a different displacement effect. Sometimes the combination of two displacement filter actions, from the same, but flipped, image, produces a better-looking edge distortion effect.

Note that because this is a pixel-based action, you can only make a displacement work on a text layer if that layer is first turned into pixels (i.e. rasterised) first. Do this by right-clicking the appropriate layer and choosing 'Rasterise'. In Elements this process is the same but it's called Simplifying...

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