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1 .. _cds2014_cpp: | |
2 | |
3 ################################## | |
4 A Saga of Fire and Water - Codelab | |
5 ################################## | |
6 | |
7 Introduction | |
8 ------------ | |
9 | |
10 .. include:: cpp_summary.inc | |
11 | |
12 .. include:: ../nacldev/setup_app.inc | |
13 | |
14 Get the Code! | |
15 ------------- | |
16 | |
17 Rather than start from nothing, for this codelab we've provided | |
18 you with a zip file containing a starting point. | |
19 | |
20 Download the codelab:: | |
21 | |
22 curl http://nacltools.storage.googleapis.com/cds2014/cds2014_cpp.zip -O | |
23 | |
24 Unzip it:: | |
25 | |
26 unzip cds2014_cpp.zip | |
27 | |
28 Go into the codelab directory:: | |
29 | |
30 cd cds2014_cpp | |
31 | |
32 Create a new local git repo:: | |
33 | |
34 git init | |
35 | |
36 Add everything:: | |
37 | |
38 git add . | |
39 | |
40 Commit it:: | |
41 | |
42 git commit -am "initial" | |
43 | |
44 While working, you can see what you've changed by running:: | |
45 | |
46 git diff | |
47 | |
48 | |
49 Fire is cool, let's burn some stuff... | |
50 -------------------------------------- | |
51 | |
52 Indulging your inner child, lets make some virtual fire! | |
53 Use the following shockingly intuitive incantation:: | |
54 | |
55 make fire | |
56 | |
57 You should now see a small popup window, smoldering away. | |
58 If you click, you can make more fire! | |
59 I think that's pretty cool, but then I selected | |
60 the institution of higher learning I attended based | |
61 on the integral role fire played in its campus life. | |
62 | |
63 Water | |
64 ----- | |
65 | |
66 Remarkably, not everyone enjoys the primal illusion of fire. | |
67 | |
68 Your task in this codelab is to transform the rising fire | |
69 effect you see before you, into a beautiful, tranquil waterfall. | |
70 This will require digging into some C++ code. | |
71 | |
72 Before you begin, you'll want to copy our fire program to a new name, | |
73 since you might decide later that you like fire better, I know I do:: | |
74 | |
75 cp fire.cc water.cc | |
76 | |
77 For this codelab, you'll only need to change `water.cc`. | |
78 | |
79 The task of turning fire into water involves two key challenges: | |
80 | |
81 * Alter the red-yellow palette of fire into a blue-green one. | |
82 * Reverse upward rising flame into downward falling water. | |
83 * Seed the waterfall from the top instead of the bottom. | |
84 | |
85 At this point you'll want to open up `water.cc` in the editor you | |
86 picked earlier. | |
87 | |
88 I see a red door and I want it painted... blue | |
89 ============================================== | |
90 | |
91 While PPAPI's 2D graphics API uses multi-component RGB pixels, | |
92 our flame effect is actually monochrome. A single intensity | |
93 value is used in the flame simulation. This is then converted | |
94 to color based on a multi-color gradient. | |
95 To alter the color-scheme, locate this palette, and exchange | |
96 the red component for blue. | |
97 | |
98 Hint: Focus your energies on the CreatePalette function. | |
99 | |
100 You can test you changes at any time with:: | |
101 | |
102 make water | |
103 | |
104 What goes up... | |
105 =============== | |
106 | |
107 Now there's the small matter of gravity. | |
108 While smoke, and well flame, rises, we want our water to go down. | |
109 | |
110 The simulation of fire loops over each pixel, | |
111 bottom row to top row, | |
112 diffusing "fire stuff" behind the sweep. | |
113 You'll want to reverse this. | |
114 Note the simulation buffer is stored in |row_major| from bottom to top. | |
115 Accesses of + width and - width are used to reach rows above and below | |
116 the current line. | |
117 | |
118 .. |row_major| raw:: html | |
119 | |
120 <a href="http://en.wikipedia.org/wiki/Row-major_order" | |
121 target="_blank">Row-major order</a> | |
122 | |
123 Hint: You'll need to change the y loop direction in the UpdateFlames function. | |
124 | |
125 Up high, down low | |
126 ================= | |
127 | |
128 While you can now use the mouse to inject a trickle of water. | |
129 The small line of blue at the bottom isn't much of a waterfall. | |
130 Move it to the top to complete the effect. | |
131 | |
132 Hint: You'll want to change the area that the UpdateCoals function mutates. | |
133 | |
134 | |
135 What you've learned | |
136 ------------------- | |
137 | |
138 In addition to learning a new appreciation for fire, you've also made water... | |
139 And while dusting off your C/C++ image manipulation skills, | |
140 you've discovered how easy it is to modify, build, | |
141 and run a NaCl application that uses PPAPI. | |
142 | |
143 2D graphics is fun, but now you're ready to check out the wealth of | |
144 other | |
145 `PPAPI interfaces available | |
146 <http://src.chromium.org/viewvc/chrome/trunk/src/ppapi/cpp/>`_. | |
binji
2014/11/14 19:19:17
point to docs instead of source control?
bradn
2014/11/14 23:55:35
Done.
| |
147 | |
148 While our in-browser environment is rapidly evolving | |
149 to become a complete development solution, | |
150 for the broadest range of development options, check out the | |
151 `NaCl SDK | |
152 <https://developer.chrome.com/native-client/sdk/download>`_. | |
153 | |
154 For questions, concerns, and help contact us at | |
155 `native-client-discuss@googlegroups.com | |
156 <https://groups.google.com/forum/#!forum/native-client-discuss>`_. | |
157 | |
158 I hope this codelab has lit a fire in you to go out there, | |
159 and bring an awesome C/C++ application to NaCl or PNaCl today! | |
160 | |
161 | |
162 .. include:: ../nacldev/cleanup_app.inc | |
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