Setting up a camera to match a photograph in 3D space can be a daunting task for anyone if you don't know how to go about it correctly. In this tutorial I will demonstrate a real simple way of matching a camera in 3D studio max to a photograph background for easy compositing.
Before going in to the tutorial I am going to assume to know the basics of Photoshop 3D Studio Max and Perspectives
One vanishing point
One vanishing point is seen in roads rail tracks and any objects that are made up of lines either directly parallel with the viewer's line of sleepers)
Two-point perspective can be used to draw the same objects as one-point perspective, rotated. One point represents one set of parallel lines, the other point represents the other set. Looking at a box from a corner, one wall would head towards one vanishing point, the other wall would head towards the opposite vanishing point.
Three-point perspective is usually used for buildings seen from above (or below). In addition to the two vanishing points from before, one for each wall, there is now one for how those walls recede into the ground. This third vanishing point will be below the ground. Looking up at a tall building is another common example of the third vanishing point. This time the third vanishing point is high in space.
Part 1: Preparing the Background image in Photoshop
For this tutorial I am going to demonstrate the process on a simple 1 point perspective image so that it is easier for first timers to follow but generally the rules apply to all forms of perspective.
Fig 1: The background image used
First of all create a new file in Photoshop, the size isn't too important (I have a 2000x2000 template that I use whenever I need to).
Then create 3 horizontal guide lines (top, dead centre, and bottom), and Shift drag your background image into the Photoshop file so that it sits dead centre.
Fig 2: The set-up file with guides
Drag your top and bottom guide lines so that they snap to the top and bottom of your image (as shows in fig 3a & b).
Fig 3a & b: Adjusting the guides and image
Now you need to shift and drag your back ground image up or down so that the horizon/eye level runs along the centre guide line.
Readjust the top and bottom guidelines so that they are once again snap to the top and bottom of the background image.
Using the select tool select the region between the top and middle guide (note if you needed to move your image down you would need to select the region between the middle and bottom guides) and move the selection (select > transform selection] to the opposite side of the middle guide.
Fig 4: Transforming the selection