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51-01.md

@@ -8,12 +8,12 @@ Chapter 51\
 
 ### Using Backface Removal to Eliminate Hidden Surfaces {#Heading2}
 
-As I’m fond of pointing out, computer animation isn’t a matter of
+As I'm fond of pointing out, computer animation isn't a matter of
 mathematically exact modeling or raw technical prowess, but rather of
-fooling the eye and the mind. That’s especially true for 3-D animation,
-where we’re not only trying to convince viewers that they’re seeing
+fooling the eye and the mind. That's especially true for 3-D animation,
+where we're not only trying to convince viewers that they're seeing
 objects on a screen—when in truth that screen contains no objects at
-all, only gaggles of pixels—but we’re also trying to create the illusion
+all, only gaggles of pixels—but we're also trying to create the illusion
 that the objects exist in three-space, possessing four dimensions
 (counting movement over time as a fourth dimension) of their own. To
 make this magic happen, we must provide cues for the eye not only to
@@ -23,16 +23,16 @@ and rapid and smooth screen updates; the whole deal is considerably more
 difficult to pull off on a PC than 2-D animation.
 
   ------------------- ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
-  ![](images/i.jpg)   *In some senses, however, 3-D animation is easier than 2-D. Because there’s more going on in 3-D animation, the eye and brain tend to make more assumptions, and so are more apt to see what they expect to see, rather than what’s actually there.*
+  ![](images/i.jpg)   *In some senses, however, 3-D animation is easier than 2-D. Because there's more going on in 3-D animation, the eye and brain tend to make more assumptions, and so are more apt to see what they expect to see, rather than what's actually there.*
   ------------------- ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 
-If you’re piloting a (virtual) ship through a field of thousands of
-asteroids at high speed, you’re unlikely to notice if the more distant
+If you're piloting a (virtual) ship through a field of thousands of
+asteroids at high speed, you're unlikely to notice if the more distant
 asteroids occasionally seem to go right through each other, or if the
-topographic detail on the asteroids’ surfaces sometimes shifts about a
-bit. You’ll be busy viewing the asteroids in their primary role, as
+topographic detail on the asteroids' surfaces sometimes shifts about a
+bit. You'll be busy viewing the asteroids in their primary role, as
 objects to be navigated around, and the mere presence of topographic
-detail will suffice; without being aware of it, you’ll fill in the
+detail will suffice; without being aware of it, you'll fill in the
 blanks. Your mind will see the topography peripherally, recognize it for
 what it is supposed to be, and, unless the landscape does something
 really obtrusive such as vanishing altogether or suddenly shooting a
@@ -43,21 +43,21 @@ To what extent can you rely on the eye and mind to make up for
 imperfections in the 3-D animation process? In some areas, hardly at
 all; for example, jaggies crawling along edges stick out like red flags,
 and likewise for flicker. In other areas, though, the human perceptual
-system is more forgiving than you’d think. Consider this: At the end of
+system is more forgiving than you'd think. Consider this: At the end of
 *Return of the Jedi*, in the battle to end all battles around the Death
 Star, there is a sequence of about five seconds in which several
 spaceships are visible in the background. One of those spaceships (and
-it’s not very far in the background, either) looks a bit unusual. What
+it's not very far in the background, either) looks a bit unusual. What
 it looks like is a sneaker. In fact, it *is* a sneaker—but unless you
-know to look for it, you’ll never notice it, because your mind is busy
-making simplifying assumptions about the complex scene it’s seeing—and
+know to look for it, you'll never notice it, because your mind is busy
+making simplifying assumptions about the complex scene it's seeing—and
 one of those assumptions is that medium-sized objects floating in space
 are spaceships, unless proven otherwise. (Thanks to Chris Hecker for
-pointing this out. I’d never have noticed the sneaker, myself, without
+pointing this out. I'd never have noticed the sneaker, myself, without
 being tipped off—which is, of course, the whole point.)
 
-If it’s good enough for George Lucas, it’s good enough for us. And with
-that, let’s resume our quest for realtime 3-D animation on the PC.
+If it's good enough for George Lucas, it's good enough for us. And with
+that, let's resume our quest for realtime 3-D animation on the PC.
 
 ### One-sided Polygons: Backface Removal {#Heading3}
 
@@ -72,8 +72,8 @@ implemented this pipeline, we were able to watch as a polygon rotated
 about its Y axis, and were able to move the polygon around in space
 freely.
 
-One of the drawbacks of the previous chapter’s approach was that the
-polygon had two visible sides. Why is that a drawback? It isn’t,
+One of the drawbacks of the previous chapter's approach was that the
+polygon had two visible sides. Why is that a drawback? It isn't,
 necessarily, but in our case we want to use polygons to build solid
 objects with continuous surfaces, and in that context, only one side of
 a polygon is visible; the other side always faces the inside of the
@@ -85,7 +85,7 @@ had the outside face pointing toward the viewer). On average, half the
 polygons in an object could be instantly rejected by a test of this
 sort. Such testing of polygon visibility goes by a number of names in
 the literature, including backplane culling, backface removal, and
-assorted variations thereon; I’ll refer to it as *backface removal*.
+assorted variations thereon; I'll refer to it as *backface removal*.
 
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