UPDATE 6/12/2009
Actually, why not just use paths in Photoshop? They allow you to draw them outside the canvas area as needed. Seems like the best solution of all, but read on for other ideas...
UPDATE 6/11/2009
Bert Monroy mentioned in Deke McClelland's Martini Hour 017 that he does all his perspective work in Adobe Illustrator on the infinite workspace that extends well beyond the document. Great idea!
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You know your lines need to converge to a common vanishing point. But what do you do when that vanishing point is so far along the horizon that it is not within your composition?
Here's a guide I put together on how to plan a perspective grid in Photoshop when the vanishing points are far off the page.
First a little background on layers and reference points in Photoshop.
Make a straight line on an otherwise new, transparent layer. In this case I have made a somewhat diagonal line, so that the line's tips are in the upper left and lower right corners of the line's imaginary bounding box.
Hit ctrl-t (in Windows) to transform the layer containing the line. You'll see a bounding box around the line, and a special point in the middle of the box called the reference point. Hover your cursor near the edge of the box until to see a curved arrow. The curved arrow indicates that the layer can be rotated. Drag the layer. Notice how by default it rotates around the reference point in the center of the layer.
While you are transforming the layer, look up in the options box along the top of the Photoshop CS2 workspace. See that little tic-tac-toe board? That is one way of controling the location of a layer's reference point.
Hit the white square in the upper left corner of the tic-tac-toe board before you rotate your layer. See now how the line itself rotates about one of its own end points?
The line will rotate about the end point that is located in the upper left hand corner of its bounding box.
Can you guess where I'm going with this?
Enough groundwork. Let's begin:
Go to full screen mode.
Zoom way out and establish a distant vanishing point. Use your talent and instinct to figure where your vanishing point needs to be -- that is outside the scope of this tutorial.
You may find guides useful here. Guides are the blue lines you get when you drag off of the rulers at the edge of the image.
Establish a line from your vanishing point through your image and out the other side.
Hit ctrl-t (on Windows) to transform your line layer at will.
but make sure you use the reference point locator first -- you want to rotate the line about the layer's corner, not the layer's center!
thanks for puttting the time to make this, a learned a few tricks
Sweet! Practical perspective I can actually use, thanks in no small part to my restrictive desk!
Thank you for the tutorial! =D
Thank you! Finally, a fast and easy perspective reference in photoshop revealed!
Man, it could even be printed out to make a grid for non-digital work.
Good job!