simple-yet-powerful-srt-subtitle-parser-cpp

simple-yet-powerful-srt-subtitle-parser-cpp copied to clipboard

I'm going to use a few terms throughout this video that not everyone might understand.

2 00:00:06,719 --> 00:00:10,960 A plane is a mathematical term for a square or rectangle.

3 00:00:10,960 --> 00:00:14,560 This is mostly the walls, ceiling and floor.

4 00:00:14,560 --> 00:00:19,519 Vertices are the corners of said planes, the singular being vertex.

5 00:00:19,519 --> 00:00:23,519 Polygons are another term for surfaces derived from computer science rather than maths.

6 00:00:23,519 --> 00:00:26,519 It's going to be used interchangeably with plane.

7 00:00:26,559 --> 00:00:31,160 To do something recursively means a process must repeat itself over and over until an

8 00:00:31,160 --> 00:00:33,399 end goal is met to solve a problem.

9 00:00:33,399 --> 00:00:37,079 A data type is a way data is classified in programming.

10 00:00:37,079 --> 00:00:43,000 For example, a string, which are words or a series of letters, and int, which is an

11 00:00:43,000 --> 00:00:44,960 integer, a typical number.

12 00:00:44,960 --> 00:00:50,200 There are different kinds of numbers as well, such as float for precise decimal numbers,

13 00:00:50,200 --> 00:00:53,039 and long for, well, long numbers.

14 00:00:53,039 --> 00:01:02,039 Of the total size of the games industry today, around 20% are games within the shooter genre.

15 00:01:02,039 --> 00:01:07,760 Around a fifth of games in this $300 billion industry are shooters, most of them being

16 00:01:07,760 --> 00:01:09,480 first person shooters.

17 00:01:09,480 --> 00:01:14,379 The amount of money generated by and riding on the success of this singular genre in this

18 00:01:14,379 --> 00:01:16,359 industry is stupefying.

19 00:01:16,359 --> 00:01:21,200 The first person shooter as developed early on was a huge departure from every other kind

20 00:01:21,200 --> 00:01:23,560 of game that existed at the time.

21 00:01:23,560 --> 00:01:28,159 Games at the time, PC games especially, were often slow or methodical.

22 00:01:28,159 --> 00:01:34,040 The personal computer platform was known for careful and considered games, turn-based strategy,

23 00:01:34,040 --> 00:01:37,520 grand RPGs with a slowly unfolding world.

24 00:01:37,520 --> 00:01:41,240 Often times these games would be indistinguishable from a spreadsheet.

25 00:01:41,240 --> 00:01:43,600 Action was the realm of console gaming.

26 00:01:43,600 --> 00:01:47,640 Platformers were the most immediate real-time action-packed games available, and besides

27 00:01:47,640 --> 00:01:52,340 notable games like Duke Nukem and Commander Keen, people didn't really play those kind

28 00:01:52,340 --> 00:01:54,319 of action games on PC.

29 00:01:54,319 --> 00:01:57,319 This was until the advent of the first person shooter.

30 00:01:57,319 --> 00:02:01,299 Suddenly people were hit with this visceral representation of violence.

31 00:02:01,299 --> 00:02:03,599 They represented something which films could not.

32 00:02:03,599 --> 00:02:06,439 You inhabit a world through the lens of the character.

33 00:02:06,439 --> 00:02:10,920 You are closer to the action hero than ever before in any medium in history.

34 00:02:10,920 --> 00:02:16,199 What is widely agreed upon as the first first person shooter ever is Maze War, developed

35 00:02:16,199 --> 00:02:20,799 in 1973, that's the same year Britain joined the European Union, Dark Side of the Moon

36 00:02:20,799 --> 00:02:24,199 was released, and the United States announced it would withdraw from Vietnam.

37 00:02:24,199 --> 00:02:28,759 It was developed for NASA computers by Steve Colleade, Greg Thompson and Howard Palmer.

38 00:02:28,759 --> 00:02:31,679 It was constructed with simple wireframe graphics.

39 00:02:31,679 --> 00:02:36,120 People had the idea of adding multiple players using networking, then connecting over the

40 00:02:36,120 --> 00:02:37,120 ARPANET.

41 00:02:37,120 --> 00:02:38,120 Then it took off.

42 00:02:38,120 --> 00:02:40,799 We saw other first person shooter games after that point.

43 00:02:40,800 --> 00:02:46,600 Spasm or Space Sim in 1974, Battlezone for arcades in 1980.

44 00:02:46,600 --> 00:02:51,520 Besides these few examples, for the majority of the decades following its inception, the

45 00:02:51,520 --> 00:02:56,000 first person perspective was known mostly for its association with the role playing

46 00:02:56,000 --> 00:02:58,320 genre, for example games like Ultima.

47 00:02:58,320 --> 00:03:03,520 Now, first person shooting did technically exist, but you were merely shooting projectiles

48 00:03:03,520 --> 00:03:04,520 at your friends.

49 00:03:04,520 --> 00:03:08,439 You weren't inhabiting a character, you weren't the action hero fighting bad guys,

50 00:03:08,439 --> 00:03:11,359 That was until Wolfenstein 3D.

51 00:03:11,359 --> 00:03:17,000 id Software was founded in 1991 by four former soft disk employees, John and Adrian Carmack,

52 00:03:17,000 --> 00:03:21,240 no relation they just happened to have the same name, Tom Hall and John Romero.

53 00:03:21,240 --> 00:03:24,000 This was the same year the Soviet Union fell.

54 00:03:24,000 --> 00:03:26,340 Carmack is going to be more important later on.

55 00:03:26,340 --> 00:03:31,199 They originally began with a Mario clone named Dangerous Dave before the company was officially

56 00:03:31,199 --> 00:03:32,199 founded.

57 00:03:32,199 --> 00:03:35,560 This was mainly to show off the beginnings of John Carmack's technical wizardry, encoding

58 00:03:35,560 --> 00:03:38,560 an efficient 2D side scrolling graphics renderer.

59 00:03:38,560 --> 00:03:43,780 The early 90s, when everything was a dark and edgy statement, the satanic inversion

60 00:03:43,780 --> 00:03:46,539 between PC and console was no exception.

61 00:03:46,539 --> 00:03:49,560 PC graphics using software rendering were terrible.

62 00:03:49,560 --> 00:03:54,900 John Carmack developed his adaptive tile refresh for the PC to compete with the raw computational

63 00:03:54,900 --> 00:03:58,599 power of the Super Nintendo, a true beast.

64 00:03:58,599 --> 00:04:02,240 Adaptive tile refresh meant that slightly more of the game world could be included in

65 00:04:02,240 --> 00:04:04,640 the screen buffer, just outside of view.

66 00:04:04,640 --> 00:04:07,360 This meant they could render smooth 2D scrolling.

67 00:04:07,360 --> 00:04:11,400 It also made the sprite animations independent from screen scrolling.

68 00:04:11,400 --> 00:04:16,120 This little bit of code magic powered their games, including the Commander Keen series.

69 00:04:16,120 --> 00:04:20,520 The Commander Keen series was spread through shareware, with subsequent episodes releasing

70 00:04:20,520 --> 00:04:24,340 over the next year or so for purchase from Apogee, their publisher.

71 00:04:24,340 --> 00:04:29,280 This shareware model would be important because it would be used in their subsequent games.

72 00:04:29,280 --> 00:04:33,200 Speaking of subsequent games…

73 00:04:33,279 --> 00:04:36,879 Wolfenstein 3D began development in 1991.

74 00:04:36,879 --> 00:04:42,199 It would use the raycasting technique earlier employed in id's Catacomb 3D.

75 00:04:42,199 --> 00:04:47,079 Raycasting was a rendering technique necessitated again by the limited processing power of PCs

76 00:04:47,079 --> 00:04:48,079 at the time.

77 00:04:48,079 --> 00:04:51,319 PC master race just can't stop losing.

78 00:04:51,319 --> 00:04:55,800 PCs almost all used software rendering, rather than a dedicated graphics chip.

79 00:04:55,800 --> 00:05:00,879 The shareware model involved getting the game on as many PCs as possible.

80 00:05:00,879 --> 00:05:03,079 Raycasting was the solution to help them do this.

81 00:05:03,079 --> 00:05:07,479 Raycasting allowed their game to run on basically any PC.

82 00:05:07,479 --> 00:05:11,740 Raycasting means you're able to draw only the surfaces which are in the player's field

83 00:05:11,740 --> 00:05:12,740 of view.

84 00:05:12,740 --> 00:05:15,000 This helped massively in saving processing power.

85 00:05:15,000 --> 00:05:16,000 But how does it work?

86 00:05:16,000 --> 00:05:21,519 In effect, a ray is cast, from the player to the geometry, to the nearest object blocking

87 00:05:21,519 --> 00:05:22,519 its path.

88 00:05:22,519 --> 00:05:25,839 In Wolfenstein, none of the levels were truly 3D.

89 00:05:25,839 --> 00:05:28,799 Every level was drawn out on a flat 2D plane.

90 00:05:28,800 --> 00:05:34,120 The program scans horizontally, checking that every pixel on the horizontal axis has something

91 00:05:34,120 --> 00:05:35,120 drawn in it.

92 00:05:35,120 --> 00:05:39,480 If there's nothing drawn in a position, a pixel column will be drawn out.

93 00:05:39,480 --> 00:05:43,699 This is simplified from the process of ray tracing, where this process is done for every

94 00:05:43,699 --> 00:05:46,600 single pixel, rather than every pixel column.

95 00:05:46,600 --> 00:05:51,040 The distance between the viewer, or the camera or player, they all have the same meaning,

96 00:05:51,040 --> 00:05:53,439 and the nearest piece of geometry, is obtained.

97 00:05:53,439 --> 00:05:58,400 The height of the pixel column is calculated using the distance from point of intersection

98 00:05:58,400 --> 00:06:00,880 in the direction the player is facing.

99 00:06:00,880 --> 00:06:04,440 It uses trigonometry to find this point of intersection.

100 00:06:04,440 --> 00:06:09,240 This effectively allowed them to give the illusion of distance, to render a 3D scene.

101 00:06:09,240 --> 00:06:14,620 This makes the process of rendering 3D much easier, as a line, that line being distance

102 00:06:14,620 --> 00:06:20,560 from player to geometry, directly transforms to a line, that being the height of the rendered

103 00:06:20,560 --> 00:06:21,560 column.

104 00:06:21,560 --> 00:06:24,480 This process is done multiple times every single second.

105 00:06:24,560 --> 00:06:29,360 The planes in the scene had been texture mapped, where an image is applied to a 3D surface.

106 00:06:29,360 --> 00:06:34,560 When the columns are drawn, they are really drawing slices of these wall textures at different

107 00:06:34,560 --> 00:06:35,560 sizes.

108 00:06:35,560 --> 00:06:40,319 The height of the column being drawn is smaller when the plane, that being the wall, is further

109 00:06:40,319 --> 00:06:41,319 away from you.

110 00:06:41,319 --> 00:06:45,879 The textures are scaled appropriately to the size of the wall, relative to the player.

111 00:06:45,879 --> 00:06:49,319 This gave the world of Wolfenstein so much believability for the time.

112 00:06:49,319 --> 00:06:52,839 You were no longer just navigating wireframe mazes.

113 00:06:52,839 --> 00:06:57,959 You were an action hero, BJ Blazkowicz, infiltrating a Nazi castle.

114 00:06:57,959 --> 00:07:00,920 The walls were adorned with flags of the German Reich.

115 00:07:00,920 --> 00:07:03,199 You felt closer to the world than ever before.

116 00:07:03,199 --> 00:07:06,240 You were interacting with a true 3D space.

117 00:07:06,240 --> 00:07:08,500 This process was, however, flawed.

118 00:07:08,500 --> 00:07:13,279 In Wolfenstein 3D, there was no verticality at all, no difference in elevation, only the

119 00:07:13,279 --> 00:07:16,800 walls had texture, the ceiling and floor had to be flat colours.

120 00:07:16,800 --> 00:07:20,680 If they wanted texture on the ceiling and floor, they would have had to add horizontal

121 00:07:20,680 --> 00:07:21,680 scanlines.

122 00:07:21,680 --> 00:07:24,079 You were still ultimately navigating a maze.

123 00:07:24,079 --> 00:07:27,879 A colourful maze with Nazis in it, but a maze nonetheless.

124 00:07:27,879 --> 00:07:31,319 Wolfenstein 3D was released in May 1992.

125 00:07:31,319 --> 00:07:34,960 The sequel, Spear of Destiny, was released later in the same year.

126 00:07:34,960 --> 00:07:39,560 While the rest of the id team was working on Spear of Destiny, John Carmack, the ascetic,

127 00:07:39,560 --> 00:07:42,560 high priest of technology, locked himself away to study.

128 00:07:42,560 --> 00:07:47,199 He would brainstorm the revolutionary tech that would power their next massive game,

129 00:07:47,199 --> 00:07:51,480 the next game that the rest of the team would start working on in September 1992.

130 00:07:51,480 --> 00:07:56,079 It would be something inspired by evil dead, brutal and violent.

131 00:07:56,079 --> 00:08:02,040 The name, Green and Pissed, was ultimately passed up for the much snappier Doom.

132 00:08:02,040 --> 00:08:08,000 Doom would launch in 1993, the game would truly be able to transport you into a world.

133 00:08:08,000 --> 00:08:10,620 The levels truly felt like places.

134 00:08:10,660 --> 00:08:16,100 The architecture of Doom consisted of supernatural science facilities, with Giger-esque and hellish

135 00:08:16,100 --> 00:08:17,740 environments as well.

136 00:08:17,740 --> 00:08:23,060 The enemies were a combination of horror and sci-fi with cybernetically enhanced demons.

137 00:08:23,060 --> 00:08:27,959 The architecture, over the top setting and violence was inspired by films such as Evil

138 00:08:27,959 --> 00:08:29,180 Dead and Alien.

139 00:08:29,180 --> 00:08:34,620 The floors could now be angled, they could now have multiple levels with stairs and elevators.

140 00:08:34,620 --> 00:08:38,120 Tools of toxic fluid surrounded these risen platforms.

141 00:08:38,120 --> 00:08:40,220 It was truly 3D.

142 00:08:40,220 --> 00:08:41,540 But it wasn't really.

143 00:08:41,540 --> 00:08:46,180 They were yet to achieve the full 6 degrees of freedom that John Romero wanted.

144 00:08:46,180 --> 00:08:47,899 This wouldn't happen until Quake.

145 00:08:47,899 --> 00:08:51,700 Rumours couldn't be stacked on top of each other, there was no vertical aim, the game

146 00:08:51,700 --> 00:08:54,779 was entirely played on the horizontal axis.

147 00:08:54,779 --> 00:08:58,560 The thing is, vertical aim was actually possible at the time.

148 00:08:58,560 --> 00:09:02,860 They could have limited the enemies' vertical hitboxes to the size of the sprite, but they

149 00:09:02,860 --> 00:09:03,860 didn't.

150 00:09:03,860 --> 00:09:06,620 Not because they couldn't, but to save processing power.

151 00:09:06,620 --> 00:09:09,779 You see, Doom was still using software rendering.

152 00:09:09,819 --> 00:09:13,939 This shareware model relied on getting their games on as many computers as possible, like

153 00:09:13,939 --> 00:09:14,939 I said.

154 00:09:14,939 --> 00:09:18,740 It was essentially the beginning of the free to play game model we have today.

155 00:09:18,740 --> 00:09:22,980 They aimed for the IBM PC, for machines running DOS.

156 00:09:22,980 --> 00:09:27,480 They had to sell their game to university students and wagies who were bored at work

157 00:09:27,480 --> 00:09:29,500 so they could run office tournaments.

158 00:09:29,500 --> 00:09:33,860 They didn't calculate the enemies' vertical hitbox so that they could save memory.

159 00:09:33,860 --> 00:09:38,419 They didn't want to give the enemies' hitboxes a height value, just have another factor to

160 00:09:38,419 --> 00:09:39,419 calculate.

161 00:09:39,459 --> 00:09:43,059 These levels were drawn on a 2D plane, like Wolfenstein.

162 00:09:43,059 --> 00:09:46,099 Just this time, the map creator is quite different.

163 00:09:46,099 --> 00:09:50,659 The ground is divided into sectors, this will be very important later.

164 00:09:50,659 --> 00:09:55,139 Each sector has two associated values, ceiling height and floor height.

165 00:09:55,139 --> 00:09:59,099 Well, it has several associated values, but those are two important ones.

166 00:09:59,099 --> 00:10:03,339 This is also why one room could not be placed above another and why every surface had to

167 00:10:03,339 --> 00:10:06,339 be made out of a flat square or rectangle.

168 00:10:06,340 --> 00:10:10,500 Another reason that vertical aim couldn't have worked is due to how the texture mapping

169 00:10:10,500 --> 00:10:11,500 worked.

170 00:10:11,500 --> 00:10:16,060 One game that did have vertical aim and levels on top of each other, before Quake and not

171 00:10:16,060 --> 00:10:19,420 that long after Doom, was Bungie's Marathon.

172 00:10:19,420 --> 00:10:22,820 And look what happens when you look up and down in that game.

173 00:10:22,820 --> 00:10:25,379 The textures start to distort.

174 00:10:25,379 --> 00:10:29,379 This is because the game, like Doom, uses affine texture mapping.

175 00:10:29,379 --> 00:10:34,780 This, like many of the other methods, was done to save memory on the processor by taking

176 00:10:34,779 --> 00:10:37,139 advantage of CPU caching.

177 00:10:37,139 --> 00:10:43,699 Basically, what happens is that texture coordinates are linearly interpolated, using screen space

178 00:10:43,699 --> 00:10:49,699 distance between vertices, rather than the actual 3D in-engine distance between them.

179 00:10:49,699 --> 00:10:54,000 The distance between points on a plane remains the same when you look up and down.

180 00:10:54,000 --> 00:10:58,379 What this means is that perspective when looking up and down is not accounted for.

181 00:10:58,379 --> 00:11:02,240 You know how pixels on a texture start to warp as you get closer?

182 00:11:02,240 --> 00:11:07,639 It looks like a straight line from far away begins to turn inward as closer pixels get

183 00:11:07,639 --> 00:11:11,399 larger, while more distant pixels get smaller.

184 00:11:11,399 --> 00:11:17,279 This doesn't happen in Doom, because accounting for perspective is taxing on 90s computers.

185 00:11:17,279 --> 00:11:21,539 You know how the game only draws things in columns to save processing time?

186 00:11:21,539 --> 00:11:25,840 They'd have had to do vertical scans as well as horizontal scans.

187 00:11:25,840 --> 00:11:32,080 Newer ports of Doom with newer rendering engines made for new hardware like GZDoom obviously

188 00:11:32,920 --> 00:11:33,920 don't have this limitation.

189 00:11:33,920 --> 00:11:37,960 As such, they use more current texture mapping and don't have this issue.

190 00:11:37,960 --> 00:11:40,720 But all of these concessions weren't enough.

191 00:11:40,720 --> 00:11:45,560 John Carmack's coding brilliance met its most devious enemy yet.

192 00:11:45,560 --> 00:11:46,560 Stairs.

193 00:11:46,560 --> 00:11:51,720 John Romero came out with a really way-out and strange idea on his early incarnation

194 00:11:51,720 --> 00:11:52,720 of E1M2.

195 00:11:52,720 --> 00:11:58,720 Yes, he wanted to mix things up with the earth-shattering invention of stairs.

196 00:11:58,720 --> 00:12:03,600 You see, just raycasting alone wasn't enough to efficiently optimise the game.

197 00:12:03,600 --> 00:12:07,680 Raycasting saves memory by only rendering things which are visible to the player.

198 00:12:07,680 --> 00:12:12,519 However, surfaces on the inside of these stairs were visible to the existing algorithm.

199 00:12:12,519 --> 00:12:15,320 Thus, they were drawn when they shouldn't have been.

200 00:12:15,320 --> 00:12:20,360 You see, for 3D rendering to not waste performance, they need to draw as few surfaces, as few

201 00:12:20,360 --> 00:12:21,840 planes as possible.

202 00:12:21,840 --> 00:12:27,639 This necessitates occlusion culling, or visible surface determination, or backface culling.

203 00:12:27,679 --> 00:12:33,319 Basically, the renderer should only draw what is in the player's field of view.

204 00:12:33,319 --> 00:12:37,080 There need to be absolutely no overdraw whatsoever.

205 00:12:37,080 --> 00:12:43,080 Adding height as a variable, such as with Romero's stairs, requires a much more sophisticated

206 00:12:43,080 --> 00:12:49,000 algorithm than was present in Wolfenstein, and in id's existing rendering engine.

207 00:12:49,000 --> 00:12:53,240 There are many different rendering algorithms out there, it seems that we need to dip into

208 00:12:53,240 --> 00:12:58,680 the hypothetical algorithms to start trawling the literature for some better algorithms.

209 00:12:58,680 --> 00:13:00,440 Let's explore some of the options.

210 00:13:00,440 --> 00:13:04,120 There's the painter's algorithm, named so because, like in a painting, the background

211 00:13:04,120 --> 00:13:07,000 is rendered first with detail layered on top.

212 00:13:07,000 --> 00:13:10,960 Basically, the polygons are sorted by their distance from the viewer, and the more distant

213 00:13:10,960 --> 00:13:14,759 polygons are rendered first, and the closest polygon is rendered last.

214 00:13:14,759 --> 00:13:17,399 It is easily the most simple solution.

215 00:13:17,399 --> 00:13:24,159 It was developed in 1972, the year MASH started, as an easy to implement solution for CAD.

216 00:13:24,159 --> 00:13:29,399 It also has the worst possible case for space complexity, meaning it takes up as much memory

217 00:13:29,399 --> 00:13:31,819 as an algorithm possibly could.

218 00:13:31,819 --> 00:13:34,639 Every single surface in the field of view is drawn.

219 00:13:34,639 --> 00:13:37,120 Obviously, this isn't a good fit.

220 00:13:37,120 --> 00:13:41,399 It's more of an example from the early days of exactly what not to do.

221 00:13:41,399 --> 00:13:43,039 There's also Warnock's algorithm.

222 00:13:43,240 --> 00:13:47,439 John Warnock was the founder of Adobe, and this algorithm originated in his doctoral

223 00:13:47,439 --> 00:13:52,879 thesis in 1969, the year man landed on the moon and In the Court of the Crimson King

224 00:13:52,879 --> 00:13:53,879 was released.

225 00:13:53,879 --> 00:13:57,899 Essentially, it recursively subdivides the screen into four parts.

226 00:13:57,899 --> 00:14:01,839 What this means is it splits the screen into four windows and splits each window into four

227 00:14:01,839 --> 00:14:02,959 smaller windows.

228 00:14:02,959 --> 00:14:08,000 It does this again and again until each window is trivial to render, meaning it has only

229 00:14:08,000 --> 00:14:10,719 one or zero polygons present.

230 00:14:10,720 --> 00:14:14,960 The algorithm also checks if multiple polygons are within one window.

231 00:14:14,960 --> 00:14:19,040 If the closest polygon covers the whole window, then it is drawn.

232 00:14:19,040 --> 00:14:23,440 This is more efficient than Painter's algorithm as it renders front to back, but it's still

233 00:14:23,440 --> 00:14:25,160 not very well suited.

234 00:14:25,160 --> 00:14:30,800 It will eventually keep subdividing to a ridiculous degree, to the point where a window is smaller

235 00:14:30,800 --> 00:14:31,800 than a pixel.

236 00:14:31,800 --> 00:14:34,399 Yeah, this ain't a good fit for a game.

237 00:14:34,399 --> 00:14:38,180 You could do a z-buffer for every pixel you want to draw, check if there's anything in

238 00:14:38,180 --> 00:14:39,180 front of it.

239 00:14:39,180 --> 00:14:40,740 And check on every single pixel?

240 00:14:40,740 --> 00:14:42,740 Yeah, there's no chance in hell.

241 00:14:42,740 --> 00:14:47,700 The final solution does kinda use a z-buffer, but it doesn't do that check on every single

242 00:14:47,700 --> 00:14:50,780 pixel, it finds a much more efficient way to do it.

243 00:14:50,780 --> 00:14:51,780 No.

244 00:14:51,780 --> 00:14:57,820 In order to truly revolutionize not just gaming, but 3D graphics forever, our protagonist,

245 00:14:57,820 --> 00:15:03,340 John Carmack, needs to go to a much more inspired source, something that hadn't actually been

246 00:15:03,340 --> 00:15:04,960 implemented before.

247 00:15:04,960 --> 00:15:06,960 Something he'd just read in a white paper.

248 00:15:06,960 --> 00:15:07,960 Just a concept.

249 00:15:07,960 --> 00:15:13,019 Yes, how common is it in gaming to see people run into optimization issues and seek out

250 00:15:13,019 --> 00:15:17,259 a white paper to solve their problem, because nobody else had done it before?

251 00:15:17,259 --> 00:15:19,139 Yes, that's Carmack for you.

252 00:15:19,139 --> 00:15:23,720 We needed a renderer that would draw objects closest to the player to furthest away until

253 00:15:23,720 --> 00:15:27,580 every pixel was written to, that had no overdraw.

254 00:15:27,580 --> 00:15:32,879 The solution was in a 1980 white paper, as the same year Genesis released the reclaimed

255 00:15:32,879 --> 00:15:36,580 album, Duke, where they really came into their own.

256 00:15:37,960 --> 00:15:45,820 This 1980 white paper by Bruce Nailup was given the humble title, On Visible Surface

257 00:15:45,820 --> 00:15:49,060 Generation by Apriori Tree Structures.

258 00:15:49,060 --> 00:15:55,460 It described a rendering model we know as Binary Space Partitioning, or BSP for short.

259 00:15:55,460 --> 00:15:58,700 This was the method that would change gaming for years.

260 00:15:58,700 --> 00:16:02,300 This wasn't the first time Binary Space Partitioning was alluded to.

261 00:16:02,300 --> 00:16:08,520 A 1969 study by the Air Force of the good ol' US of A alluded to the use of partitioning

262 00:16:08,520 --> 00:16:12,000 3D scenes to solve the visible surface problem.

263 00:16:12,000 --> 00:16:17,340 The study was conducted to determine the viability of 3D for flight simulation.

264 00:16:17,340 --> 00:16:21,380 We can thank the armed forces of the United States for giving us doom.

265 00:16:21,380 --> 00:16:24,900 They explored using a matrix to track which objects are occluded.

266 00:16:24,900 --> 00:16:29,160 These of course wouldn't do so well as the size of the matrix would need to be the square

267 00:16:29,160 --> 00:16:31,760 of the number of objects in a scene.

268 00:16:31,759 --> 00:16:33,620 That wouldn't scale very well.

269 00:16:33,620 --> 00:16:39,200 It wasn't until 1980 that Binary Space Partitioning was properly realized in the white paper that

270 00:16:39,200 --> 00:16:43,860 would reach John Carmack alongside its core tenant, the binary tree.

271 00:16:43,860 --> 00:16:46,740 But what is Binary Space Partitioning anyway?

272 00:16:46,740 --> 00:16:48,779 Well, the name gives you a clue.

273 00:16:48,779 --> 00:16:52,080 Is partitioning space in a 3D environment?

274 00:16:52,080 --> 00:16:54,939 This is done using a BSP tree.

275 00:16:54,939 --> 00:16:57,100 What is a BSP tree you may ask?

276 00:16:57,100 --> 00:17:02,040 In computer science, a tree is a data structure used as a mathematical model for displaying

277 00:17:02,040 --> 00:17:03,560 certain data types.

278 00:17:03,560 --> 00:17:08,720 It's separated into nodes with parent nodes that have child nodes.

279 00:17:08,720 --> 00:17:13,279 BSP uses binary trees, binary essentially meaning two.

280 00:17:13,279 --> 00:17:18,759 A binary tree is a tree where there are two or less child nodes stemming from any given

281 00:17:18,759 --> 00:17:20,559 parent, from any node.

282 00:17:20,559 --> 00:17:23,380 There are never more than two child nodes.

283 00:17:23,380 --> 00:17:28,160 This is as opposed to a non-binary tree, which is a tree that has dyed hair and a gender

284 00:17:28,160 --> 00:17:29,320 studies degree.

285 00:17:29,320 --> 00:17:34,800 The data stored in the nodes of the binary tree are the sub-sectors of the map.

286 00:17:34,800 --> 00:17:39,640 Sub-sectors being smaller parts of those map sectors I spoke about earlier.

287 00:17:39,640 --> 00:17:45,360 Remember, each map is designed on a flat 2D map editor, with each sector having associated

288 00:17:45,360 --> 00:17:46,600 height values.

289 00:17:46,600 --> 00:17:51,880 The genius is that the map is sliced up via binary space partitioning after the map is

290 00:17:51,880 --> 00:17:52,880 built.

291 00:17:52,880 --> 00:17:58,580 Hard work is done when the map is created, rather than by the processor at runtime while

292 00:17:58,580 --> 00:18:00,340 the player is playing the game.

293 00:18:00,340 --> 00:18:06,180 The map is already split, already partitioned when the player loads it, reducing processing

294 00:18:06,180 --> 00:18:07,840 needed at runtime.

295 00:18:07,840 --> 00:18:12,980 To create the binary tree, a root node is established covering the whole map.

296 00:18:12,980 --> 00:18:19,460 After this, the map is recursively subdivided along every plane until only convex sub-sectors

297 00:18:19,460 --> 00:18:20,460 are left.

298 00:18:20,480 --> 00:18:24,120 The sectors are carved into smaller sub-sectors.

299 00:18:24,120 --> 00:18:28,900 The entire map is essentially cut in two along every single wall.

300 00:18:28,900 --> 00:18:33,799 Every time the map is cut in half, the two halves are added as nodes at the bottom of

301 00:18:33,799 --> 00:18:34,840 the tree.

302 00:18:34,840 --> 00:18:40,400 By the end, you're left with a tree where each node at the bottom of the tree represents

303 00:18:40,400 --> 00:18:42,000 a distinct sub-sector.

304 00:18:42,000 --> 00:18:45,539 Remember, this tree is entirely conceptual.

305 00:18:45,539 --> 00:18:47,500 It doesn't actually exist.

306 00:18:47,519 --> 00:18:52,920 So long as the planes don't move – vertical movement is accepted from this because vertical

307 00:18:52,920 --> 00:18:57,960 movement is a separate value – the same BSP tree can be used.

308 00:18:57,960 --> 00:19:03,480 Doom's BSP tree generation was done after levels were complete and would search for

309 00:19:03,480 --> 00:19:09,000 the best possible tree, that being the one that generates the fewest binary tree nodes.

310 00:19:09,000 --> 00:19:13,240 A binary search is performed to determine what sector the player is in.

311 00:19:13,259 --> 00:19:18,660 A binary search is when an array of pre-sorted data is searched through by continually halving

312 00:19:18,660 --> 00:19:19,660 said array.

313 00:19:19,660 --> 00:19:24,740 A search through a binary tree is, by its nature, a binary search, because every time

314 00:19:24,740 --> 00:19:29,079 you go down a node, you're removing half of the possibilities.

315 00:19:29,079 --> 00:19:33,859 After the player's sector is determined using this binary search, the sub-sectors

316 00:19:33,859 --> 00:19:38,279 are then sorted by their distance from the player – closest to furthest.

317 00:19:38,279 --> 00:19:42,279 The tree is iterated through to determine which planes to draw.

318 00:19:42,299 --> 00:19:47,220 The horizontal scanlines from raycasting are still used to track the parts of the screen

319 00:19:47,220 --> 00:19:48,859 that have been drawn over.

320 00:19:48,859 --> 00:19:53,619 This way they are able to render front to back and ensure that there is no overdraw.

321 00:19:53,619 --> 00:19:57,859 When each node is passed over in the iteration, a few things are checked.

322 00:19:57,859 --> 00:20:00,019 Has that area already been painted over?

323 00:20:00,019 --> 00:20:02,339 If so, don't bother drawing it.

324 00:20:02,339 --> 00:20:08,660 When a plane, polygon or wall is drawn, it is akin to a curtain being drawn left to right.

325 00:20:08,720 --> 00:20:14,200 To unveil an area, so to speak, whenever a curtain is seen by the player, it is unveiled

326 00:20:14,200 --> 00:20:16,040 from closest to the furthest.

327 00:20:16,040 --> 00:20:20,759 To be exact, it's the closest 256 walls that are displayed.

328 00:20:20,759 --> 00:20:26,240 Remember how height of the pixel columns drawn on screen depended on distance from the player?

329 00:20:26,240 --> 00:20:32,120 For Doom, this required determining the angle of both ends of every wall, relative to the

330 00:20:32,120 --> 00:20:33,440 player's field of view.

331 00:20:33,440 --> 00:20:38,580 In the early 90s, most processors didn't have dedicated floating-point capability.

332 00:20:38,599 --> 00:20:41,599 This is a float in programming, if you've ever heard of that.

333 00:20:41,599 --> 00:20:45,359 Basically a data type for very precise decimal numbers.

334 00:20:45,359 --> 00:20:51,659 The Doom engine had to use binary angle measurements, which avoid floats, and used a lookup table

335 00:20:51,659 --> 00:20:54,000 to determine the x coordinates.

336 00:20:54,000 --> 00:20:56,960 A lookup table is essentially a cheat sheet.

337 00:20:56,960 --> 00:21:02,359 Instead of the processor doing the maths itself, it just looks up the answer in this lookup table.

338 00:21:02,359 --> 00:21:08,559 They also used these angles for backface culling, with a simple and elegant piece of mathematics

339 00:21:08,559 --> 00:21:14,379 Backface culling basically means the renderer doesn't draw the inside of every polygon.

340 00:21:14,379 --> 00:21:18,099 It only draws the part on the outside that you actually see.

341 00:21:18,099 --> 00:21:23,339 The walls are rendered first as pixel columns from front to back, then the ceilings and

342 00:21:23,339 --> 00:21:25,819 floors using pixel rows.

343 00:21:25,819 --> 00:21:31,500 The objects such as barrels and enemies are rendered from the furthest to the closest.

344 00:21:31,500 --> 00:21:37,599 The ceilings and floors are determined using visplane underscore t, or visplanes.

345 00:21:37,600 --> 00:21:41,900 Plains were determined using height values within each sector.

346 00:21:41,900 --> 00:21:46,940 Visplanes are not constrained to single sectors, and will be continuous provided they all possess

347 00:21:46,940 --> 00:21:50,600 the same height, illumination and textures.

348 00:21:50,600 --> 00:21:53,180 Pixel rows are drawn top to bottom.

349 00:21:53,180 --> 00:21:59,080 One final thing you may wonder about Doom's graphics is why are all the enemies just pictures

350 00:21:59,080 --> 00:22:00,780 facing towards you?

351 00:22:00,780 --> 00:22:04,880 Probably something to do with them being what we call front-facing sprites.

352 00:22:04,880 --> 00:22:08,980 They're rendered last, and like I said, furthest to closest.

353 00:22:08,980 --> 00:22:11,340 That's the opposite order to the geometry.

354 00:22:11,340 --> 00:22:16,340 They are just pictures, taken from the data files and projected onto screen.

355 00:22:16,340 --> 00:22:18,840 Of course, they're a range of pictures.

356 00:22:18,840 --> 00:22:24,020 The one that is drawn depends on the player's location relative to the enemy, and the direction

357 00:22:24,020 --> 00:22:25,500 the enemy is facing.

358 00:22:25,500 --> 00:22:29,040 The enemies do actually have a full 3D hitbox.

359 00:22:29,040 --> 00:22:34,260 The pictures, as most fans know, are actually from real pictures taken of sculptures made

360 00:22:34,259 --> 00:22:35,400 by the artists.

361 00:22:35,400 --> 00:22:41,519 So, John Carmack was faced with a fierce issue in the problem of visible surface determination.

362 00:22:41,519 --> 00:22:46,759 He had to find a solution that was both incredibly fast and very accurate.

363 00:22:46,759 --> 00:22:53,000 BSP doesn't completely solve the visible surface determination problem, but it is one

364 00:22:53,000 --> 00:22:56,900 of the most reliable and efficient methods of optimisation.

365 00:22:56,900 --> 00:22:59,039 It saw massive acceptance.

366 00:22:59,039 --> 00:23:04,339 BSPs were evolved and made their way into Quake's dramatically improved game engine

367 00:23:04,339 --> 00:23:09,819 when they took on Michael Abrash and finally figured out the full six degrees of freedom.

368 00:23:09,819 --> 00:23:15,220 From there, it was in every FPS, and I mean all of them.

369 00:23:15,220 --> 00:23:16,859 Half-Life and Half-Life 2?

370 00:23:16,859 --> 00:23:17,859 Every Source game.

371 00:23:17,859 --> 00:23:19,819 Counter-Strike to Left 4 Dead.

372 00:23:19,819 --> 00:23:21,500 The Halo series used it.

373 00:23:21,500 --> 00:23:24,579 You know the Scarab from Halo 2 is actually a BSP object?

374 00:23:24,579 --> 00:23:27,980 Yes, it's a moving piece of level geometry.

375 00:23:27,980 --> 00:23:33,039 Many would say it's a sign of Carmack's genius that he took an idea from concept to

376 00:23:33,039 --> 00:23:34,839 mainstream solution.

377 00:23:34,839 --> 00:23:41,839 He did all this crazy work in between supercharging Ferraris and becoming a judo master.

378 00:23:41,839 --> 00:23:44,519 One time, he got locked inside a building.

379 00:23:44,519 --> 00:23:49,759 Instead of, say, waiting for security or calling a locksmith, he devised a brilliant solution.

380 00:23:49,759 --> 00:23:54,759 He'd luckily gone to a Renaissance Fair earlier, where he bought a medieval battle axe.

381 00:23:54,759 --> 00:23:58,779 Also, naturally, he smashed down the door with his mighty axe.

382 00:23:58,779 --> 00:24:01,539 He was rich so he could afford to get the door fixed.

383 00:24:01,539 --> 00:24:07,379 He truly is a unique figure in the gaming industry, and you can see why he's so highly

384 00:24:07,379 --> 00:24:08,379 respected.

385 00:24:08,379 --> 00:24:12,019 If you made it this far, comment, thank you John Carmack.

386 00:24:12,019 --> 00:24:17,700 The use of BSP trees has begun to be replaced over the last few years.

387 00:24:17,700 --> 00:24:20,740 Developers instead opt for things like static meshes.

388 00:24:20,740 --> 00:24:25,620 With more powerful hardware now, they can afford some level of overdraw.

389 00:24:25,620 --> 00:24:30,400 Other methods give artists more creative freedom and a much quicker workflow.

390 00:24:30,400 --> 00:24:36,420 BSP often leads to the distinct blocky look that many old games had.

391 00:24:36,420 --> 00:24:41,839 One could certainly argue that these technical limitations are what gave source maps and

392 00:24:41,839 --> 00:24:45,720 early 2000s maps in general their distinct charm.

393 00:24:45,720 --> 00:24:47,079 Their soul.

394 00:24:47,079 --> 00:24:54,079 With stark and distinct architectural choices, some magic is truly lost in busy modern day

395 00:24:54,079 --> 00:24:55,399 maps.

396 00:24:55,399 --> 00:25:01,119 Many new games have actually tried to go back to recreating these older, cleaner, more distinct

397 00:25:01,119 --> 00:25:02,119 visuals.

398 00:25:02,119 --> 00:25:07,639 BSP is still occasionally used today in prototyping levels for games, quickly blocking them out.

399 00:25:07,639 --> 00:25:11,279 It's of course still used in games such as Counter Strike Go.

400 00:25:11,279 --> 00:25:16,000 This was a big video, and naturally it took a bit of research, which I've provided links

401 00:25:16,000 --> 00:25:17,539 to in the description.

402 00:25:17,539 --> 00:25:23,960 If I got anything wrong, please feel free, in fact feel obligated, to call me out in

403 00:25:23,960 --> 00:25:24,960 the comments.

404 00:25:24,960 --> 00:25:31,359 Like, join the Discord server and subscribe with notifications on to join the nerd army

405 00:25:31,359 --> 00:25:33,000 and become a sigma male.

406 00:25:33,000 --> 00:25:34,799 Thanks for watching, goodbye.

407 00:26:03,000 --> 00:26:24,680 Bye.