photograph enhancing

[S...@adobeforums.com]

I start a new project in illustrator 12.0 using windows XP on a HP m7590n computer.......with a photograph of a motorcycle tank....My goal is to add graphics to the left and right sides of the tank....and to use a plotter for cutting vinyl masks of the design I have created......The plotter is a Roland Camm-1 servo GX-24........What are some ways of doing this keeping scale correct?

[James_...@adobeforums.com]

You won't be able to automatically and accurately ensure conformity to the compound curvature of the tank (if any). But assuming the size of the art, relative to the size of the tank's curvature, will let you get away with treating it as flat, the basic workflow would be like this:

1. Photgraph the tank, viewing it as "straight on" toward the center of where the art is going to be positioned as possible.

2. Put the digital photo (or scan) on your computer. Launch Illustrator. Use the Place command (File Menu) to import the image. Put it on its own layer. DoubleClick the layer in the Layer's palette and make it a Template Layer. Turn on the Dim checkbox and enter a value (I usually use 50%) to dim the photo as you work. Lock the layer so you don't accidently select the photo as you work.

3. Create another Layer, above the Template layer, on which to draw your paths.

4. Draw your cutting paths using the Pen and other drawing tools. Be sure you understand the basic operating principle of your cutter: you want your paths to be simple, explicit paths, each of which will be "followed" by the knife of the cutter. That is, whereever paths cross or shapes overlap, the cutter is going to make cross-cuts.

5. When finished with the drawing, delete the image Template layer. Save the file in a format your cutting software knows how to import. On my Roland cutter, that would be Illustrator format, but saved back to an earlier version (Illustrator 8).

6. Open the Illustrator file in your cutting software and cut the masks.

You can devise methods for dealing with the compound curvature. A couple of examples:

Example 1
Suppose the tank is one of those with a radically tapered "teardrop" shape, broad at the front, narrow at the back. The artwork is to be positioned on the top of this tank.

Think of the basic kind of curvature you are dealing with. The problem surface area is basically part of a cone, like the side of a drinking cup. After drawing your artwork in Illustrator, you can group it and then use one of the Warp effects to distort the entire artwork into a curve that would fit when wrapped around the surface.

This requires some trial-and-error, but it's not really difficult and doesn't have to be terribly time-consuming. Print the warped design from Illustrator onto a piece of paper. Wrap the print around the tank and see how it fits. Go back and adjust the warp according to what you find. Repeat the process until you have a shape that fits acceptably.

The same principle can be elaborated on more complex surface areas by using an Envelope in Illustrator to perform more involved distortions. But for surfaces common to motorcycle tanks, the pre-defined Warps should suffice.

Example 2
Now, if the artwork is going to not be confined to relatively small regions, or if portions of it need to wrap long distances around curvatures, a little more laborious preparation may be in order.

Basically, you need a grid to go by as you draw your tracing. Before photographing the tank, carefully "draw" a grid of, say, 1/2" squares on the tank with thin pinstripe tape. Then photograph the tank as before. (It will still be handy to have a photo of the tank on screen as you draw). But now, instead of just tracing the tank, draw a flat 1/2" grid in Illlustrator, with the number & arrangement of squares corresponding to that which is actually on the tank. Draw your design to conform to that grid.

Of course there are limitations to how much you can flex and stretch the masking vinyl over compound curves anyway, so you'll work the thing in sections or areas at a time. And some "tweaking" by hand of the masks when you apply them (with tape or hand-made cuts) will be likely. But you're probably accustomed to that anyway.

JET