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Preparing textures in Photoshop

Modifying perspective in CS3 By Ko Maruyama
With your digital camera in hand, you might come across some subject matter that will make a great texture, but don't have time to frame it properly.  In addition to lens distortion and lighting irregularities, simply shooting something head-on can be a problem.  In Photoshop, you can correct this very easily with the help of a filter.

Here is an image of an access cover.  I was walking along with some friends - late for a dinner - when I spotted it.  I needed some concrete textures, and the framing around the outside of the plate was great - but I didn't have time to sit around, set up a tripod and plumb the camera.  Actually, I didn't care - I knew I could easily fix it with some simple steps.






1. CROP.

In Photoshop, you can crop an image.  More importantly tho' is that Photoshop recognizes the bottom of your crop tool (little box) as the BOTTOM of the resulting image.  So if you rotate the cropping area, you will wind up with an image that is rotated. (note: this rotation will only produce a slight rotation, not "rotate CCW90")



Align the bottom of the crop with the bottom of the frame.

2. LENS CORRECTION

Select "Lens Correction" from the Distortion family of Filters.  Although this comes with a completely new dialogue box (like Liquify or Vanishing Point), it does not have its own shortcut at the top of the filter pulldown menu.

You'll need a larger screen than 800x600 (which is what I try to capture at), but if you're working on a computer built in the past 5 years, you've got that and more.

2A. GRID

You need to match the image to the grid using some simple distortion and transformation tools.  It's important that your grid doesn't match the color of your image.  At the bottom of the dialogue box is the color picker.

2B. GRID SIZE

You can change the grid size to give you a broad look at the changes that you make to your image, then, as you need to finesse the transformation, you can lower the size of the grid panels (which increases the number of squares).

Of course you can toggle the entire grid on/off with a switch located at the bottom of the window.  There is also a switch that allows you to turn the preview of your transformation on/off.

2C. ALIGN GRID

With the Align Grid tool (M), you can move the grid so that the grid lines up to the closest perpendicular areas.  Of course, you may want to modify the grid size as well.

click image for bigger view

2D. AUTO ALIGN

Using the "Straighten Tool" (A) will only rotate the image for you.  Based on the straight line that you draw with this tool, Photoshop will transform the angle of rotation for the entire image, but won't give you vertical or horizontal perspective pinching. (nor will it remove any distortion).

2E. MANUALLY CORRECT

If you have a specific lens that you use all the time, you can create settings for the adjustment, then save them.  At the bottom of the top part on the right-hand side, you can set the camera lens adjustments as the defaults.

You don't want to fix your image transformations to your defaults or presets (you never know how you'll be holding your camera next).

If the edges of the resulting image distract you, you can change them to the color of the background color chip, or (better) select EDGE EXTRUSION which will multiply the last pixel at the edge of your image to the edge of the preview window. (Note: if you intend to use the transparency produced by the transformation, turn this back to "transparency" when you're ready to accept the filter)

3. CLICK OK.

That's it.  You can continue to crop it further in order to chop out anything you don't want or need.

If you want to get the original (large) image to use, you'll be able to find it on the Ninja Crayon Blog here:

For rants, ramblings and general announcements - check out my chaotic blog in the BlogZone:
http://blogs.digitalmediaonlineinc.com/ninjacrayon/

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Ko Maruyama is a freelance animator in Los Angeles.  In addition to working on film and broadcast animations, Ko teaches at Pasadena's Art Center College of Design - focusing on motion design.  When working, writing or testing software allows, you can find him lending a hand in the After Effects board and lurking among the Cinema4D, Visual Effects and Photoshop posts within the DMNForums.
Related Keywords:tutorial, photoshop, 3D texture, lens correction, free materials

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