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+### A New Animation Framework: X-Sharp {#Heading4}
+
+Listings 52.1 through 52.10 shown earlier represent not merely faster
+animation in library form, but also a nearly complete, extensible,
+data-driven animation framework. Whereas much of the earlier animation
+code I’ve presented in this book was hardwired to demonstrate certain
+concepts, this chapter’s code is intended to serve as the basis for a
+solid animation package. Objects are stored, in their entirety, in
+customizable structures; new structures can be devised for new sorts of
+objects. Drawing, preparing for drawing, and moving are all vectored
+functions, so that variations such as shading or texturing, or even
+radically different sorts of graphics objects, such as scaled bitmaps,
+could be supported. The cube initialization is entirely data driven;
+more or different cubes, or other sorts of convex polyhedrons, could be
+added by simply changing the initialization data in Listing 52.8.
+
+Somewhere along the way in writing the material that became this section
+of the book, I realized that I had a generally useful animation package
+by the tail and gave it a name: X-Sharp. (*X* for Mode X, *sharp*
+because good animation looks sharp, and, well, who would want a flat
+animation package?)
+
+Note that the X-Sharp library as presented in this chapter (and, indeed,
+in this book) is not a fully complete 3-D library. Movement is supported
+only along the Z axis in this chapter’s version, and then in a
+non-general fashion. More interesting movement isn’t supported at this
+point because of one of the two missing features in X-Sharp:
+hidden-surface removal. (The other missing feature is general 3-D
+clipping.) Without hidden surface removal, nothing can safely overlap.
+It would actually be easy enough to perform hidden-surface removal by
+keeping the cubes in different Z bands and drawing them back to front,
+but this gets into sorting and list issues, and is not a complete
+solution—and I’ve crammed as much as will fit into one chapter’s code,
+anyway.
+
+I’m working toward a goal in this last section of the book, and there
+are many lessons to be learned and stories to be told along the way. So
+as X-Sharp grows, you’ll find its evolving implementations in the
+chapter subdirectories on the listings diskette. This chapter’s
+subdirectory, for example, contains the self-extracting archive file
+XSHARP14.EXE, (to extract its contents you simply run it as though it
+were a program) and the code in that archive is the code I’m speaking of
+specifically in this chapter, with all the limitations mentioned above.
+Chapter 53’s subdirectory, however, contains the file XSHARP15.EXE,
+which is the next step in the evolution of X-Sharp, and it is the
+version that I’ll be specifically talking about in that chapter. Later
+chapters will have their own implementations in their respective chapter
+subdirectories, in files of the form XSHARPxx.EXE, where xx is an
+ascending number indicating the version. The final and most recent
+X-Sharp version will be present in its own subdirectory called XSHARP22.
+If you’re intending to use X-Sharp in a real project, use the most
+recent version to be sure that you avail yourself of all new features
+and bug fixes.
+
+### Three Keys to Realtime Animation Performance {#Heading5}
+
+As of the previous chapter, we were at the point where we could rotate,
+move, and draw a solid cube in real time. Not too shabby...but the code
+I’m presenting in this chapter goes a bit further, rotating 12 solid
+cubes at an update rate of about 15 frames per second (fps) on a 20 MHz
+386 with a slow VGA. That’s 12 transformation matrices, 72 polygons, and
+96 vertices being handled in real time; not Star Wars, granted, but a
+giant step beyond a single cube. Run the program if you get a chance;
+you may be surprised at just how effective this level of animation is.
+I’d like to point out, in case anyone missed it, that this is fully
+*general* 3-D. I’m not using any shortcuts or tricks, like prestoring
+coordinates or pregenerating bitmaps; if you were to feed in different
+rotations or vertices, the animation would change accordingly.
+
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+* * * * *
+
+Graphics Programming Black Book © 2001 Michael Abrash