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+Chapter 52\
+ Fast 3-D Animation: Meet X-Sharp {#Heading1}
+---------------------------------
+
+### The First Iteration of a Generalized 3-D Animation Package {#Heading2}
+
+Across the lake from Vermont, a few miles into upstate New York, the
+Ausable River has carved out a fairly impressive gorge known as “Ausable
+Chasm.” Impressive for the East, anyway; you might think of it as the
+poor man’s Grand Canyon. Some time back, I did the tour with my wife and
+five-year-old, and it was fun, although I confess that I didn’t loosen
+my grip on my daughter’s hand until we were on the bus and headed for
+home; that gorge is deep, and the railings tend to be of the single-bar,
+rusted-out variety.
+
+New Yorkers can drive straight to this wonder of nature, but Vermonters
+must take their cars across on the ferry; the alternative is driving
+three hours around the south end of Lake Champlain. No problem; the
+ferry ride is an hour well spent on a beautiful lake. Or, rather, no
+problem—once you’re on the ferry. Getting to New York is easy, but, as
+we found out, the line of cars waiting to come back from Ausable Chasm
+gets lengthy about mid-afternoon. The ferry can hold only so many cars,
+and we wound up spending an unexpected hour exploring the wonders of the
+ferry docks. Not a big deal, with a good-natured kid and an entertaining
+mom; we got ice cream, explored the beach, looked through binoculars,
+and told stories. It was a fun break, actually, and before we knew it,
+the ferry was steaming back to pick us up.
+
+A friend of mine, an elementary-school teacher, helped take 65 sixth
+graders to Ausable Chasm. Never mind the potential for trouble with 65
+kids loose on a ferry. Never mind what it was like trying to herd that
+group around a gorge that looks like it was designed to swallow children
+and small animals without a trace. The hard part was getting back to the
+docks and finding they’d have to wait an hour for the next ferry. As my
+friend put it, “Let me tell you, an hour is an eternity with 65 sixth
+graders screaming the song ‘You Are My Sunshine.’”
+
+Apart from reminding you how lucky you are to be working in a quiet,
+air-conditioned room, in front of a gently humming computer, free to
+think deep thoughts and eat Cheetos to your heart’s content, this story
+provides a useful perspective on the malleable nature of time. An hour
+isn’t just an hour—it can be forever, or it can be the wink of an eye.
+Just think of the last hour you spent working under a deadline; I bet it
+went past in a flash. Which is not to say, mind you, that I recommend
+working in a bus full of screaming kids in order to make time pass more
+slowly; there are quality issues here as well.
+
+In our 3-D animation work so far, we’ve used floating-point arithmetic.
+Floating-point arithmetic—even with a floating-point processor but
+especially *without* one—is the microcomputer animation equivalent of
+working in a school bus: It takes forever to do anything, and you just
+*know* you’re never going to accomplish as much as you want to. In this
+chapter, we’ll address fixed-point arithmetic, which will give us an
+instant order-of-magnitude performance boost. We’ll also give our 3-D
+animation code a much more powerful and extensible framework, making it
+easy to add new and different sorts of objects. Taken together, these
+alterations will let us start to do some really interesting real-time
+animation.
+
+### This Chapter’s Demo Program {#Heading3}
+
+Three-dimensional animation is a complicated business, and it takes an
+astonishing amount of functionality just to get off the launching pad:
+page flipping, polygon filling, clipping, transformations, list
+management, and so forth. I’ve been building toward a critical mass of
+animation functionality over the course of this book, and this chapter’s
+code builds on the code from no fewer than five previous chapters. The
+code that’s required in order to link this chapter’s animation demo
+program is the following:
+
+-   Listing 50.1 from Chapter 50 (draw clipped line list);
+-   Listings 47.1 and 47.6 from Chapter 47 (Mode X mode set, rectangle
+    fill);
+-   Listing 49.6 from Chapter 49;
+-   Listing 39.4 from Chapter 39 (polygon edge scan); and
+-   The **FillConvexPolygon( )** function from Listing 38.1 from Chapter
+    38. Note that the **struct** keywords in **FillConvexPolygon( )**
+    must be removed to reflect the switch to typedefs in the animation
+    header file.
+
+As always, all required files are in this chapter’s subdirectory on the
+CD-ROM.
+
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+* * * * *
+
+Graphics Programming Black Book © 2001 Michael Abrash