12
Nov
Black Art of Java Game Programming by Joel
The paint() method first checks to see if the world coordinates are up-to-date. If an object s orientation has changed in any way, then the world coordinates will be dirty, meaning that they have to be recalculated. This transform only needs to be done on objects that will be rendered and are actually visible to the camera. Notice that a static object never needs to be updated, since the position and angle never change. The paint() method is supplied with a camera. Once the world coordinates are up-to-date, the method project() in camera is called with them as an argument. This method will return an array of 2D coordinates that are fed to the polyhedron s paint() method. The rest is taken care of by the fPolyhedron. Putting It All Together We have now designed a couple of classes that can be used to construct dynamic 3D scenes viewed through arbitrary cameras. This is actually part of a 3D engine, a very small part. It is now time to put these classes to work. The applet shown in Figure 11-25 will only scratch the surface of what can be done with these classes. As you will see, it will be a quick and dirty implementation just to show you how we can put them to work. In a complete 3D engine we would use another layer of classes representing scenes and actors. Figure 11-25 The rotating cubes applet The applet will construct nine instances of a polyhedron and a camera. The polyhedrons will be rotated around while the camera moves backward. To avoid flickering, we will use an offscreen image to do the rendering and then blit it to the screen. The implementation of the no-flicker applet is not a 3D issue, so it will be presented as a black-box class. Use it in good health. It can be found on the CD. Previous Table of Contents Next
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