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<body class="article toc2 toc-left">
<div id="header">
<h1>Lua Tutorial</h1>
<div id="toc" class="toc2">
<div id="toctitle">Table of Contents</div>
<ul class="sectlevel1">
<li><a href="#_tutorial_00_installation">Tutorial #00 - Installation</a>
<ul class="sectlevel2">
<li><a href="#_choose_the_right_artifact_branch">Choose the right artifact branch</a></li>
<li><a href="#_download_the_archive">Download the archive</a></li>
<li><a href="#_run_the_example_script">Run the example script</a></li>
<li><a href="#_additional_resources">Additional resources</a></li>
</ul>
</li>
<li><a href="#_tutorial_01_callbacks_and_mouse">Tutorial #01 - Callbacks and mouse</a>
<ul class="sectlevel2">
<li><a href="#_basic_application_callbacks">Basic application callbacks</a>
<ul class="sectlevel3">
<li><a href="#_on_init_and_on_shutdown">on_init() and on_shutdown()</a></li>
<li><a href="#_on_frame_start">on_frame_start()</a></li>
<li><a href="#_on_pre_init">on_pre_init()</a></li>
</ul>
</li>
<li><a href="#_mouse_input">Mouse input</a>
<ul class="sectlevel3">
<li><a href="#_on_mouse_button_released">on_mouse_button_released()</a></li>
<li><a href="#_on_mouse_moved">on_mouse_moved()</a></li>
</ul>
</li>
<li><a href="#_putting_it_all_together">Putting it all together</a></li>
</ul>
</li>
<li><a href="#_tutorial_02_text">Tutorial #02 - Text</a>
<ul class="sectlevel2">
<li><a href="#_bitmap_fonts">Bitmap fonts</a></li>
<li><a href="#_font_and_text_node_objects">Font and text node objects</a></li>
<li><a href="#_additional_text_node_functions">Additional text node functions</a>
<ul class="sectlevel3">
<li><a href="#_dynamic_size_and_position">Dynamic size and position</a></li>
<li><a href="#_color">Color</a></li>
<li><a href="#_alignment">Alignment</a></li>
</ul>
</li>
<li><a href="#_putting_it_all_together_2">Putting it all together</a></li>
</ul>
</li>
<li><a href="#_tutorial_03_audio">Tutorial #03 - Audio</a>
<ul class="sectlevel2">
<li><a href="#_audio_buffer_and_player">Audio buffer and player</a></li>
<li><a href="#_music_and_stream_players">Music and stream players</a></li>
<li><a href="#_audio_player_properties">Audio player properties</a></li>
<li><a href="#_putting_it_all_together_3">Putting it all together</a></li>
</ul>
</li>
<li><a href="#_tutorial_04_animated_sprites">Tutorial #04 - Animated sprites</a>
<ul class="sectlevel2">
<li><a href="#_spritesheets_and_rectangles">Spritesheets and rectangles</a>
<ul class="sectlevel3">
<li><a href="#_creating_an_animated_sprite">Creating an animated sprite</a></li>
<li><a href="#_defining_a_list_of_rectangles">Defining a list of rectangles</a></li>
<li><a href="#_additional_animated_sprite_functions">Additional animated sprite functions</a></li>
</ul>
</li>
<li><a href="#_putting_it_all_together_4">Putting it all together</a></li>
</ul>
</li>
<li><a href="#_tutorial_05_keyboard_and_gamepad">Tutorial #05 - Keyboard and gamepad</a>
<ul class="sectlevel2">
<li><a href="#_keyboard_input">Keyboard input</a></li>
<li><a href="#_gamepad_input">Gamepad input</a>
<ul class="sectlevel3">
<li><a href="#_mapping">Mapping</a></li>
<li><a href="#_mapped_events">Mapped events</a></li>
</ul>
</li>
<li><a href="#_putting_it_all_together_5">Putting it all together</a></li>
</ul>
</li>
<li><a href="#_tutorial_06_the_scenegraph">Tutorial #06 - The Scenegraph</a>
<ul class="sectlevel2">
<li><a href="#_the_transformations_and_the_scenegraph">The transformations and the scenegraph</a></li>
<li><a href="#_modifying_the_scenegraph">Modifying the scenegraph</a></li>
<li><a href="#_putting_it_all_together_6">Putting it all together</a></li>
</ul>
</li>
<li><a href="#_tutorial_07_mesh_sprites">Tutorial #07 - Mesh sprites</a>
<ul class="sectlevel2">
<li><a href="#_uses_of_a_mesh_sprite">Uses of a mesh sprite</a></li>
<li><a href="#_creating_a_mesh_sprite">Creating a mesh sprite</a></li>
<li><a href="#_defining_a_list_of_vertices">Defining a list of vertices</a></li>
<li><a href="#_animating_the_vertices">Animating the vertices</a></li>
<li><a href="#_putting_it_all_together_7">Putting it all together</a></li>
</ul>
</li>
</ul>
</div>
</div>
<div id="content">
<div class="sect1">
<h2 id="_tutorial_00_installation">Tutorial #00 - Installation</h2>
<div class="sectionbody">
<div class="paragraph">
<p>The nCine offers an extensive Lua API that covers most of the native C++ API and allows you to create a complete 2D game.</p>
</div>
<div class="sect2">
<h3 id="_choose_the_right_artifact_branch">Choose the right artifact branch</h3>
<div class="paragraph">
<p>To run your Lua games you need to download the nCine. The specific Lua version is recommended in this case as it is easier to setup.</p>
</div>
<div class="paragraph">
<p>You can find all the pre-compiled archives on GitHub, as branches of the same nCine Artifacts repository.</p>
</div>
<div class="paragraph">
<p>The branch name format is <code>nCine-branch-platform-compiler</code>: <a href="https://github.com/nCine/nCine-artifacts/branches/all" class="bare">https://github.com/nCine/nCine-artifacts/branches/all</a></p>
</div>
<div class="paragraph">
<p>The Lua edition is called <code>nCineLua</code> and you usually want the <code>master</code> branch.
For example, if you are on Windows, you can choose the <code>nCine-master-windows-vs2022</code> branch (compiled with the latest Visual Studio 2022) and download the archive or the installer for the nCineLua version.</p>
</div>
</div>
<div class="sect2">
<h3 id="_download_the_archive">Download the archive</h3>
<div class="paragraph">
<p>Inside the branch you will find an archive, its format depends on the choosen platform.</p>
</div>
<div class="paragraph">
<p>You can extract the archive wherever you want and that’s the only installation step needed.</p>
</div>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<i class="fa icon-note" title="Note"></i>
</td>
<td class="content">
<div class="paragraph">
<p>If you are inside a Windows branch you will also find an installer.
The nCine does not need to be installed though, you can download the ZIP archive.</p>
</div>
</td>
</tr>
</table>
</div>
</div>
<div class="sect2">
<h3 id="_run_the_example_script">Run the example script</h3>
<div class="paragraph">
<p>Inside the extracted directory you will find an binary and a data directory.</p>
</div>
<div class="paragraph">
<p>Inside the binary directory you will find some libraries and an executable.</p>
</div>
<div class="paragraph">
<p>When you run the executable it will look for a file named <code>script.lua</code>, first in its same directory and then in the data one.</p>
</div>
<div class="paragraph">
<p>You can put your <code>script.lua</code> in either directories or you can execute a different script.
To do that open a command prompt and give the path of your script as the first parameter.</p>
</div>
<div class="paragraph">
<p>For your data files (like textures or sounds), you can use an absolute path or a path relative to the executable directory.
You can also put them in the data directory and use the default data path value returned by <code>ncine.fs.get_data_path()</code>.</p>
</div>
</div>
<div class="sect2">
<h3 id="_additional_resources">Additional resources</h3>
<div class="paragraph">
<p>For a complete Lua API documentation, check the LDoc one at: <a href="https://ncine.github.io/docs/lua_master/" class="bare">https://ncine.github.io/docs/lua_master/</a></p>
</div>
<div class="paragraph">
<p>The nCine wiki offers further information: <a href="https://github.com/nCine/nCine/wiki/Getting-Started-with-Lua">Getting Started with Lua</a> and <a href="https://github.com/nCine/nCine/wiki/Getting-Started-with-Lua-VSCode)">Getting Started with Lua (VSCode)</a>.</p>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_tutorial_01_callbacks_and_mouse">Tutorial #01 - Callbacks and mouse</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_basic_application_callbacks">Basic application callbacks</h3>
<div class="paragraph">
<p>One of the first concepts to learn is the life cycle of your application and the associated event callbacks.</p>
</div>
<div class="paragraph">
<p>Callback functions are automatically called by the framework in particular moments during the life of the game, for example at the beginning of a frame or at shutdown.</p>
</div>
<div class="paragraph">
<p>Let’s write a small example that uses them.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="lua">nc = ncine
function nc.on_init()
texture_ = nc.texture.new(nc.fs.get_data_path().."textures/texture2.png")
local resolution = nc.application.get_resolution()
pos_ = {x = resolution.x * 0.5, y = resolution.y * 0.5}
sprite_ = nc.sprite.new(nc.application.get_rootnode(), texture_, pos_)
angle_ = 0
end
function nc.on_frame_start()
angle_ = angle_ + 2 * nc.application.get_frame_time()
local radius = nc.application.get_width() * 0.2
local newpos = {x = pos_.x + radius * math.sin(angle_), y = pos_.y + radius * math.cos(angle_)}
nc.sprite.set_position(sprite_, newpos)
end
function nc.on_shutdown()
nc.sprite.delete(sprite_)
nc.texture.delete(texture_)
end</code></pre>
</div>
</div>
<div class="paragraph">
<p>The first line is just a way to create a shorter alias for the <code>ncine</code> table: the API access point.</p>
</div>
<div class="sect3">
<h4 id="_on_init_and_on_shutdown">on_init() and on_shutdown()</h4>
<div class="paragraph">
<p>The <code>on_init()`function is called only once, at the beginning of your application. Here we are creating a new texture and a new sprite using the special `new()</code> function.</p>
</div>
<div class="paragraph">
<p>The <code>on_shutdown()</code> function is its mirror, it is called before the application quits and should be used to free any resources created for the game: there is one <code>delete()</code> for each <code>new()</code> we called earlier.</p>
</div>
<div class="paragraph">
<p>All functions that work on objects created with a <code>new()</code> need those objects as their first parameter, and <code>delete()</code> is no exception.</p>
</div>
<div class="paragraph">
<p>To create a texture object we just need the filename of an image file. You can use an absolute path but in this example we are using the <code>data/</code> directory by asking the filesystem table <code>fs</code> for the default data path.</p>
</div>
<div class="paragraph">
<p>Next we create a sprite object by passing four parameters to the <code>sprite.new()</code> function: a parent node, a texture object, and the X and Y coordinates of the initial position.</p>
</div>
<div class="paragraph">
<p>As a parent node we use the root node of the scenegraph by calling the <code>get_rootnode()</code> function of the <code>application</code> table. Every sprite that you want to display on screen needs to be a child of this node or to have an ancestor that is a child of this node.</p>
</div>
<div class="paragraph">
<p>The other function from the <code>application</code> table, <code>get_resolution</code>, returns the resolution of the screen and it is used here to place the sprite at the center of the screen.</p>
</div>
</div>
<div class="sect3">
<h4 id="_on_frame_start">on_frame_start()</h4>
<div class="paragraph">
<p>The <code>on_frame_start()</code> function is where most of the game logic happens, it is called once at the beginning of each frame and allows you to update objects, like move sprite arounds, play sounds, and so on.</p>
</div>
<div class="paragraph">
<p>In this example we move the sprite in a circle path by using some simple trigonometry and the Lua math library.</p>
</div>
<div class="paragraph">
<p>We increment the <code>angle_</code> variable and use it to update the sprite position with the <code>sprite.set_position()</code> function. By using the time elapsed since last frame, we keep a stable rotation regardless of frame time oscillations.</p>
</div>
</div>
<div class="sect3">
<h4 id="_on_pre_init">on_pre_init()</h4>
<div class="paragraph">
<p>We can make the example a bit more flexible by configuring some aspects before our application or the framework even initialize.</p>
</div>
<div class="paragraph">
<p>For this we can use the <code>on_pre_init()</code> callback. It receives a configuration table that we can modify before returning it.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="lua">function nc.on_pre_init(cfg)
cfg.resolution = {x = 1280, y = 720}
cfg.window_title = "nCine example"
return cfg
end</code></pre>
</div>
</div>
<div class="paragraph">
<p>There are many more variables in this table, but for this example we are just setting the initial window resolution and title.</p>
</div>
</div>
</div>
<div class="sect2">
<h3 id="_mouse_input">Mouse input</h3>
<div class="sect3">
<h4 id="_on_mouse_button_released">on_mouse_button_released()</h4>
<div class="paragraph">
<p>Even if we a have a moving sprite on screen, this example is still boring: we cannot interact with it.</p>
</div>
<div class="paragraph">
<p>Let’s remedy to this by adding the ability to move the sprite around with the mouse.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="lua">function nc.on_mouse_button_released(event)
if event.button == nc.mouse_button.LEFT then
pos_ = {x = event.x, y = event.y}
end
end</code></pre>
</div>
</div>
<div class="paragraph">
<p>The <code>on_mouse_button_released()</code> function is called every time the user releases a mouse button. It receives an event table with additional information, like which button was released.</p>
</div>
<div class="paragraph">
<p>We are performing this check by comparing the <code>button</code> variable with the <code>mouse_button.LEFT</code> constant value. Those special constant values are usually written with capital letters.</p>
</div>
<div class="paragraph">
<p>If the user released the left button, we update the <code>pos_</code> variable that will be used as the center of the rotation animation in the <code>on_frame_start()</code> function.</p>
</div>
<div class="paragraph">
<p>The coordinates of the mouse at the time a button was released are accessible in the <code>x</code> and <code>y</code> variables of the same table.</p>
</div>
</div>
<div class="sect3">
<h4 id="_on_mouse_moved">on_mouse_moved()</h4>
<div class="paragraph">
<p>You will soon discover that smashing the mouse button is not an optimal way for continuously updating the sprite position. For this you need a different function.</p>
</div>
<div class="paragraph">
<p>The <code>on_mouse_moved()</code> function is called every time the mouse is moved and receives a state table that you can query in a way similar to the event one of <code>on_mouse_button_released()</code>.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="lua">function nc.on_mouse_moved(state)
if state.is_left_down then
pos_ = {x = state.x, y = state.y}
end
end</code></pre>
</div>
</div>
<div class="paragraph">
<p>In this snippet we first check if we are moving the mouse while pressing the left mouse button by checking the value of the <code>is_left_down</code> boolean variable, then we use the <code>x</code> and <code>y</code> variables to update the position.</p>
</div>
</div>
</div>
<div class="sect2">
<h3 id="_putting_it_all_together">Putting it all together</h3>
<div class="listingblock">
<div class="title">Complete example #01</div>
<div class="content">
<pre class="rouge highlight"><code data-lang="lua">nc = ncine
function nc.on_pre_init(cfg)
cfg.resolution = {x = 1280, y = 720}
cfg.window_title = "nCine example"
return cfg
end
function nc.on_init()
texture_ = nc.texture.new(nc.fs.get_data_path().."textures/texture2.png")
local resolution = nc.application.get_resolution()
pos_ = {x = resolution.x * 0.5, y = resolution.y * 0.5}
sprite_ = nc.sprite.new(nc.application.get_rootnode(), texture_, pos_.x, pos_.y)
angle_ = 0
end
function nc.on_frame_start()
angle_ = angle_ + 2 * nc.application.get_frame_time()
local radius = nc.application.get_width() * 0.2
local newpos = {x = pos_.x + radius * math.sin(angle_), y = pos_.y + radius * math.cos(angle_)}
nc.sprite.set_position(sprite_, newpos)
end
function nc.on_shutdown()
nc.sprite.delete(sprite_)
nc.texture.delete(texture_)
end
function nc.on_mouse_button_released(event)
if event.button == nc.mouse_button.LEFT then
pos_ = {x = event.x, y = event.y}
end
end
function nc.on_mouse_moved(state)
if state.is_left_down then
pos_ = {x = state.x, y = state.y}
end
end</code></pre>
</div>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_tutorial_02_text">Tutorial #02 - Text</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_bitmap_fonts">Bitmap fonts</h3>
<div class="paragraph">
<p>With the latest tutorial you learnt how to load a texture and create a sprite from it.
In this one you will see how to load a font and display some text on screen.</p>
</div>
<div class="paragraph">
<p>nCine uses bitmap fonts: they are special textures that contains all the characters.
The information about how to render a text from those textures is contained in a FNT file. It is a text file that tells where every character is located inside the texture.</p>
</div>
<div class="paragraph">
<p>To create a font texture and the corresponding FNT description file you can use the <a href="https://www.angelcode.com/products/bmfont/">Bitmap Font Generator</a> or other tools that support AngelCode’s format.</p>
</div>
</div>
<div class="sect2">
<h3 id="_font_and_text_node_objects">Font and text node objects</h3>
<div class="paragraph">
<p>To create a new font object you can use the <code>font.new()</code> function. As usual, remember to call <code>font.delete()</code> when you are done with it.</p>
</div>
<div class="paragraph">
<p>The parameters for this function are the path to a FNT file and the path to a texture file (be careful, it is <strong>not</strong> a texture object).</p>
</div>
<div class="paragraph">
<p>To display some text on screen you also need a text node. Just like a sprite, it has to be a child of the root node or have an ancestor that is a child of the root node.</p>
</div>
<div class="paragraph">
<p>You also need to associate it with the font to use: <code>textnode.new(rootnode, font, 256)</code>.</p>
</div>
<div class="paragraph">
<p>The last parameter is the maximum length allowed for the text to be displayed. You can tune this value around the use you want to do of your text node, to optimize performance and memory usage.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="lua">nc = ncine
function nc.on_init()
local rootnode = nc.application.get_rootnode()
font_ = nc.font.new(nc.fs.get_data_path().."fonts/DroidSans32_256.fnt",
nc.fs.get_data_path().."fonts/DroidSans32_256.png")
local resolution = nc.application.get_resolution()
textnode_ = nc.textnode.new(rootnode, font_, 256)
nc.textnode.set_position(textnode_, resolution.x * 0.5, resolution.y * 0.5)
end
function nc.on_frame_start()
nc.textnode.set_string(textnode_, string.format("FPS: %.2f", 1.0 / nc.application.get_frame_time()))
end
function nc.on_shutdown()
nc.textnode.delete(textnode_)
nc.font.delete(font_)
end</code></pre>
</div>
</div>
</div>
<div class="sect2">
<h3 id="_additional_text_node_functions">Additional text node functions</h3>
<div class="sect3">
<h4 id="_dynamic_size_and_position">Dynamic size and position</h4>
<div class="paragraph">
<p>We can make this example even better by positioning the text in one of the screen’s corners.</p>
</div>
<div class="paragraph">
<p>To do that we need to know how tall and how wide is the text that we are rendering.
We can do exactly that with the <code>get_width()</code> and the <code>get_height()</code> functions.</p>
</div>
<div class="paragraph">
<p>If we are changing the string each frame, like in this example, we need to reposition the text each frame to take into account the changes in size.</p>
</div>
</div>
<div class="sect3">
<h4 id="_color">Color</h4>
<div class="paragraph">
<p>Changing the color of a text node is simple: you just have to call the <code>set_color()</code> function with the four color channel values (red, green, blue, and alpha).</p>
</div>
<div class="paragraph">
<p>For example, <code>nc.textnode.set_color(textnode_, 1, 1, 0, 1)</code> will make the text yellow.</p>
</div>
</div>
<div class="sect3">
<h4 id="_alignment">Alignment</h4>
<div class="paragraph">
<p>When the string to render has at least one <code>\n</code> character the text will span multiple lines.</p>
</div>
<div class="paragraph">
<p>In this case you can choose how to align them (left, right, or center) with the <code>set_alignment()</code> function.</p>
</div>
<div class="paragraph">
<p>For example, <code>nc.textnode.set_alignment(textnode_, nc.text_alignment.CENTER)</code> will align multiple lines at the center.</p>
</div>
<div class="paragraph">
<p>To set the alignment, we have used again a special constant value. There are three values: <code>nc.text_alignment.LEFT</code>, <code>nc.text_alignment.RIGHT</code>, and <code>nc.text_alignment.CENTER</code>.</p>
</div>
</div>
</div>
<div class="sect2">
<h3 id="_putting_it_all_together_2">Putting it all together</h3>
<div class="listingblock">
<div class="title">Complete example #02</div>
<div class="content">
<pre class="rouge highlight"><code data-lang="lua">nc = ncine
function nc.on_pre_init(cfg)
cfg.resolution = {x = 1280, y = 720}
cfg.window_title = "nCine example"
cfg.console_log_level = nc.log_level.INFO
return cfg
end
function nc.on_init()
local rootnode = nc.application.get_rootnode()
font_ = nc.font.new(nc.fs.get_data_path().."fonts/DroidSans32_256.fnt",
nc.fs.get_data_path().."fonts/DroidSans32_256.png")
textnode_ = nc.textnode.new(rootnode, font_, 256)
nc.textnode.set_color(textnode_, 1, 1, 0, 1)
nc.textnode.set_alignment(textnode_, nc.text_alignment.LEFT)
end
function nc.on_frame_start()
local str = string.format("FPS: %.2f\nFrame time: %.2f ms", 1.0 / nc.application.get_frame_time(), 1000 * nc.application.get_frame_time())
nc.textnode.set_string(textnode_, str)
nc.textnode.set_position(textnode_, nc.textnode.get_width(textnode_) * 0.5,
nc.application.get_height() - nc.textnode.get_height(textnode_) * 0.5)
end
function nc.on_shutdown()
nc.textnode.delete(textnode_)
nc.font.delete(font_)
end</code></pre>
</div>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_tutorial_03_audio">Tutorial #03 - Audio</h2>
<div class="sectionbody">
<div class="sect2">
<h3 id="_audio_buffer_and_player">Audio buffer and player</h3>
<div class="paragraph">
<p>To play sounds and music you have to first load the audio data and then associate it with a player.
The concept is similar to textures and sprites, or fonts and text nodes.</p>
</div>
<div class="paragraph">
<p>In this case the two objects are <code>audio_buffer</code> and <code>audio_buffer_player</code>.</p>
</div>
<div class="paragraph">
<p>The <code>audio_buffer.new()</code> function takes the path to a WAV or OGG Vorbis file, while the <code>audio_buffer_player.new()</code> function takes the audio buffer object you have just created.</p>
</div>
<div class="paragraph">
<p>Once the player has been created, you can use the <code>play()</code>, <code>pause()</code>, and <code>stop()</code> functions to control it.</p>
</div>
<div class="listingblock">
<div class="content">
<pre class="rouge highlight"><code data-lang="lua">nc = ncine
function nc.on_init()
audio_buffer_ = nc.audio_buffer.new(nc.fs.get_data_path().."sounds/coins.ogg")
player_ = nc.audio_buffer_player.new(audio_buffer_)
end
function nc.on_mouse_button_released(event)
nc.audio_buffer_player.stop(player_)
nc.audio_buffer_player.play(player_)
end
function nc.on_shutdown()
nc.audio_buffer_player.delete(player_)
nc.audio_buffer.delete(audio_buffer_)
end</code></pre>