Chromium Code Reviews| Index: native_client_sdk/src/doc/cds2014/cpp.rst |
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| +.. _cds2014_cpp: |
| + |
| +################################## |
| +A Saga of Fire and Water - Codelab |
| +################################## |
| + |
| +Introduction |
| +------------ |
| + |
| +.. include:: cpp_summary.inc |
| + |
| +.. include:: ../nacldev/setup_app.inc |
| + |
| +Get the Code! |
| +------------- |
| + |
| +Rather than start from nothing, for this codelab we've provided |
| +you with a zip file containing a starting point. |
| + |
| +Download the codelab:: |
| + |
| + curl http://nacltools.storage.googleapis.com/cds2014/cds2014_cpp.zip -O |
| + |
| +Unzip it:: |
| + |
| + unzip cds2014_cpp.zip |
| + |
| +Go into the codelab directory:: |
| + |
| + cd cds2014_cpp |
| + |
| +Create a new local git repo:: |
| + |
| + git init |
| + |
| +Add everything:: |
| + |
| + git add . |
| + |
| +Commit it:: |
| + |
| + git commit -am "initial" |
| + |
| +While working, you can see what you've changed by running:: |
| + |
| + git diff |
| + |
| + |
| +Fire is cool, let's burn some stuff... |
| +-------------------------------------- |
| + |
| +Indulging your inner child, lets make some virtual fire! |
| +Use the following shockingly intuitive incantation:: |
| + |
| + make fire |
| + |
| +You should now see a small popup window, smoldering away. |
| +If you click, you can make more fire! |
| +I think that's pretty cool, but then I selected |
| +the institution of higher learning I attended based |
| +on the integral role fire played in its campus life. |
| + |
| +Water |
| +----- |
| + |
| +Remarkably, not everyone enjoys the primal illusion of fire. |
| + |
| +Your task in this codelab is to transform the rising fire |
| +effect you see before you, into a beautiful, tranquil waterfall. |
| +This will require digging into some C++ code. |
| + |
| +Before you begin, you'll want to copy our fire program to a new name, |
| +since you might decide later that you like fire better, I know I do:: |
| + |
| + cp fire.cc water.cc |
| + |
| +For this codelab, you'll only need to change `water.cc`. |
| + |
| +The task of turning fire into water involves two key challenges: |
| + |
| + * Alter the red-yellow palette of fire into a blue-green one. |
| + * Reverse upward rising flame into downward falling water. |
| + * Seed the waterfall from the top instead of the bottom. |
| + |
| +At this point you'll want to open up `water.cc` in the editor you |
| +picked earlier. |
| + |
| +I see a red door and I want it painted... blue |
| +============================================== |
| + |
| +While PPAPI's 2D graphics API uses multi-component RGB pixels, |
| +our flame effect is actually monochrome. A single intensity |
| +value is used in the flame simulation. This is then converted |
| +to color based on a multi-color gradient. |
| +To alter the color-scheme, locate this palette, and exchange |
| +the red component for blue. |
| + |
| +Hint: Focus your energies on the CreatePalette function. |
| + |
| +You can test you changes at any time with:: |
| + |
| + make water |
| + |
| +What goes up... |
| +=============== |
| + |
| +Now there's the small matter of gravity. |
| +While smoke, and well flame, rises, we want our water to go down. |
| + |
| +The simulation of fire loops over each pixel, |
| +bottom row to top row, |
| +diffusing "fire stuff" behind the sweep. |
| +You'll want to reverse this. |
| +Note the simulation buffer is stored in |row_major| from bottom to top. |
| +Accesses of + width and - width are used to reach rows above and below |
| +the current line. |
| + |
| +.. |row_major| raw:: html |
| + |
| + <a href="http://en.wikipedia.org/wiki/Row-major_order" |
| + target="_blank">Row-major order</a> |
| + |
| +Hint: You'll need to change the y loop direction in the UpdateFlames function. |
| + |
| +Up high, down low |
| +================= |
| + |
| +While you can now use the mouse to inject a trickle of water. |
| +The small line of blue at the bottom isn't much of a waterfall. |
| +Move it to the top to complete the effect. |
| + |
| +Hint: You'll want to change the area that the UpdateCoals function mutates. |
| + |
| + |
| +What you've learned |
| +------------------- |
| + |
| +In addition to learning a new appreciation for fire, you've also made water... |
| +And while dusting off your C/C++ image manipulation skills, |
| +you've discovered how easy it is to modify, build, |
| +and run a NaCl application that uses PPAPI. |
| + |
| +2D graphics is fun, but now you're ready to check out the wealth of |
| +other |
| +`PPAPI interfaces available |
| +<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.
|
| + |
| +While our in-browser environment is rapidly evolving |
| +to become a complete development solution, |
| +for the broadest range of development options, check out the |
| +`NaCl SDK |
| +<https://developer.chrome.com/native-client/sdk/download>`_. |
| + |
| +For questions, concerns, and help contact us at |
| +`native-client-discuss@googlegroups.com |
| +<https://groups.google.com/forum/#!forum/native-client-discuss>`_. |
| + |
| +I hope this codelab has lit a fire in you to go out there, |
| +and bring an awesome C/C++ application to NaCl or PNaCl today! |
| + |
| + |
| +.. include:: ../nacldev/cleanup_app.inc |