In case the first two chapters of this book have not drilled this into you so completely that you now have nightmares about it every night, we're going to repeat it once again. All of the cheats in this book are about one thing: fooling the user into seeing 3D on a 2D screen. There are many different methods for achieving this. At the very high end, we have complicated 3D engines that allow the creation and traversing of 3D worlds , complete with photo-realistic lighting and textures. On the other end of the scale, there's the kind of faux-3D that we're talking about in this book. Since Flash doesn't have a built-in 3D engine or the computational firepower for creating such an engine in ActionScript, we need to resort to trickery . This chapter is about using one of the most important clues that our brain processes when judging depth and perspective: the relative sizes of various objects. In other words, scale.
We take for granted that when we look down a long corridor or across a wide plain to a person in the distance, that person appears smaller to our eyes than if she were standing right in front of us. Although the person appears smaller in our view, our brain knows that this is because she is standing far away and not because she's pulling an "Alice in Wonderland" on us. In other words, our brain understands that people don't shrink, so it interprets impossibly small people as standing far away. In fact, this is not an automatic reaction but one that is socially learned. We can manipulate the fact that our brains have learned to correlate size with distance to create the effect of the third dimension on our flat 2D monitors .
Creating the illusion of 3D is a bit more complicated than simply scattering a couple of objects of different sizes on the stage. The realism of your scenes will depend on factors such as lighting, camera angle, and depth of field. If this is beginning to sound like an introductory film course, there's a reason for that: what we're doing is very similar to shooting a film. Whereas with film we have a camera that we can manipulate to affect depth of field, exposure, and focus, we have to create these effects manually in Flash. Similarly, when filming we use carefully placed lights (or the sun and reflectors) to control shadows. When creating our 3D scenes, we have to visualize imaginary light sources and shade our objects accordingly . In creating the upcoming effects, we're going to look at the stage in a new way: as the viewfinder of our camera, looking out into a 3D world that we will sculpt using all manner of trickery to create lighting, depth of field, and perspective. To do this, we'll start out using the 2D drawing tools in Flash and, later on, a little bit of ActionScript.