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223 lines
12 KiB
HTML
223 lines
12 KiB
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<title>Irrlicht Engine Tutorial</title>
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<body bgcolor="#FFFFFF" leftmargin="0" topmargin="0" marginwidth="0" marginheight="0">
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<br>
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<table width="95%" border="0" cellspacing="0" cellpadding="2" align="center">
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<tr>
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<td bgcolor="#666699" width="10"><b><a href="http://irrlicht.sourceforge.net" target="_blank"><img src="../../media/irrlichtlogo.jpg" width="88" height="31" border="0"></a></b></td>
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<td bgcolor="#666699" width="100%">
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<div align="center">
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<div align="center"></div>
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<div align="left"><b><font color="#FFFFFF">Tutorial 3.CustomSceneNode</font></b></div>
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</div>
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</td>
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</tr>
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<tr bgcolor="#eeeeff">
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<td height="90" colspan="2">
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<div align="left">
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<p>This Tutorial is a tutorial for more advanced developers. If you are
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currently just playing around with the Irrlicht engine, please look
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at other examples first. This tutorial shows how to create a custom
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scene node and how to use it in the engine. A custom scene node is needed,
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if you want to implement a render technique, the Irrlicht Engine is
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currently not supporting. For example you can write a indoor portal
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based renderer or a advanced terrain scene node with it. With creating
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custom scene nodes, you can easily extend the Irrlicht Engine and adapt
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it to your needs.</p>
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<p>I will keep the tutorial simple: Keep everything very short, everything
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in one .cpp file, and I'll use the engine here as in all other tutorials.
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At the end of the tutorial, the result will look like the image below.
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This looks not very exciting, but it is a complete customized scene
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node and a good point to start from creating you own scene nodes.</p>
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<p align="center"><img src="../../media/003shot.jpg" width="259" height="204"><br>
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</p>
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</div>
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</td>
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</tr>
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</table>
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<br>
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<table width="95%" border="0" cellspacing="0" cellpadding="2" align="center">
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<tr>
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<td bgcolor="#666699"> <div align="center"><b><font color="#FFFFFF"></font></b></div>
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<b><font color="#FFFFFF">Lets start!</font></b></td>
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</tr>
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<tr>
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<td height="90" bgcolor="#eeeeff" valign="top"> <div align="left">
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<p>To start, I include the header files, use the irr namespace, and tell
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the linker to link with the .lib file. </p>
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<table width="95%" border="0" cellspacing="2" cellpadding="0" bgcolor="#CCCCCC" align="center">
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<tr>
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<td> <pre>#include <irrlicht.h></pre> <pre>using namespace irr;</pre> <pre>#pragma comment(lib, "Irrlicht.lib")</pre></td>
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</tr>
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</table>
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<p>Here comes the most sophisticated part of this tutorial: The class
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of our very own custom scene node. To keep it simple,<br>
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our scene node will not be an indoor portal renderer nor a terrain scene
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node, but a simple tetraeder, a 3d object consiting of 4 connected vertices,
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which only draws itself and does nothing more.</p>
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<p>To let our scene node be able to be inserted into the Irrlicht Engine
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scene, the class we create needs only be derived from the ISceneNode
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class and has to override some methods.</p>
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<table width="95%" border="0" cellspacing="2" cellpadding="0" bgcolor="#CCCCCC" align="center">
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<tr>
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<td> <pre>class CSampleSceneNode : public scene::ISceneNode<br>{</pre> </td>
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</tr>
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</table>
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<p>First, we declare some member variables, to hold data for our tetraeder:
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The bounding box, 4 vertices, and<br>
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the material of the tetraeder.</p>
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<table width="95%" border="0" cellspacing="2" cellpadding="0" bgcolor="#CCCCCC" align="center">
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<tr>
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<td> <pre>core::aabbox3d<f32> Box;<br>video::S3DVertex Vertices[4];<br>video::SMaterial Material;</pre> </td>
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</tr>
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</table>
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<p>The parameters of the constructor specify the parent of the scene node,
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a pointer to the scene manager, and an id of the scene node. In the
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constructor itself, we call the parent classes constructor, set some
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properties of the material we use to draw the scene node and create
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the 4 vertices of the tetraeder we will draw later. </p>
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<table width="95%" border="0" cellspacing="2" cellpadding="0" bgcolor="#CCCCCC" align="center">
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<tr>
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<td> <pre>public:</pre> <pre>CSampleSceneNode(scene::ISceneNode* parent, scene::ISceneManager* mgr, s32 id)
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: scene::ISceneNode(parent, mgr, id)
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{
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Material.Wireframe = false;
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Material.Lighting = false;</pre>
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<pre> Vertices[0] = video::S3DVertex(0,0,10, 1,1,0,video::SColor(255,0,255,255),0,1);
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Vertices[1] = video::S3DVertex(10,0,-10, 1,0,0,video::SColor(255,255,0,255),1,1);
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Vertices[2] = video::S3DVertex(0,20,0, 0,1,1,video::SColor(255,255,255,0),1,0);
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Vertices[3] = video::S3DVertex(-10,0,-10, 0,0,1,video::SColor(255,0,255,0),0,0);
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</pre></td>
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</tr>
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</table>
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<br>
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The Irrlicht Engine needs to know the bounding box of your scene node.
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It will use it for doing automatic culling and other things. Hence we
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need to create a bounding box from the 4 vertices we use. If you do not
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want the engine to use the box for automatic culling, and/or don't want
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to create the box, you could also write<br>
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<font face="Courier New, Courier, mono">AutomaticCullingEnabled = false;</font>.<br>
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<br>
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<table width="95%" border="0" cellspacing="2" cellpadding="0" bgcolor="#CCCCCC" align="center">
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<tr>
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<td> <pre> Box.reset(Vertices[0].Pos);<br> for (s32 i=1; i<4; ++i)<br> Box.addInternalPoint(Vertices[i].Pos);
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}</pre> </td>
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</tr>
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</table>
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<br>
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<p>Before it is drawn, the OnPreRender() method of every scene node in
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the scene is called by the scene manager. If the scene node wishes to
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draw itself, it may register itself in the scene manager to be drawn.
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This is necessary to tell the scene manager when it should call the
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::render method. For example normal scene nodes render their content
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one after another, while stencil buffer shadows would like to be drawn
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after all other scene nodes. And camera or light scene nodes need to
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be rendered before all other scene nodes (if at all). <br>
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So here we simply register the scene node to get rendered normally.
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If we would like to let it be rendered like cameras or light, we would
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have to call SceneManager->registerNodeForRendering(this, SNRT_LIGHT_AND_CAMERA);
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<br>
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After this, we call the OnPreRender-method of the base class ISceneNode,
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which simply lets also all the child scene nodes of this node register
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themselves. </p>
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</div>
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<table width="95%" border="0" cellspacing="2" cellpadding="0" bgcolor="#CCCCCC" align="center">
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<tr>
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<td> <pre>virtual void OnPreRender()<br>{<br> if (IsVisible)<br> SceneManager->registerNodeForRendering(this);
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ISceneNode::OnPreRender();
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}</pre> </td>
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</tr>
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</table>
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<p>In the render() method most of the interresting stuff happenes: The Scene
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node renders itself. We override this method and draw the tetraeder.</p>
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<table width="95%" border="0" cellspacing="2" cellpadding="0" bgcolor="#CCCCCC" align="center">
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<tr>
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<td> <pre>virtual void render()<br>{<br> u16 indices[] = { 0,2,3, 2,1,3, 1,0,3, 2,0,1 };
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video::IVideoDriver* driver = SceneManager->getVideoDriver();</pre>
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<pre> driver->setMaterial(Material);
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driver->setTransform(video::ETS_WORLD, AbsoluteTransformation);
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driver->drawIndexedTriangleList(&Vertices[0], 4, &indices[0], 4);
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}</pre> </td>
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</tr>
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</table>
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<p> At least, we create three small additional methods. GetBoundingBox()
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returns the bounding box of this scene node, <br>
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GetMaterialCount() returns the amount of materials in this scene node
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(our tetraeder only has one material), and getMaterial() returns the material
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at an index. Because we have only one material here, we can return the
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only one material, assuming that no one ever calls getMaterial() with
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an index greater than 0. </p>
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<table width="95%" border="0" cellspacing="2" cellpadding="0" bgcolor="#CCCCCC" align="center">
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<tr>
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<td><pre> virtual const core::aabbox3d<f32>& getBoundingBox() const<br> {<br> return Box;<br> }</pre> <pre> virtual u32 getMaterialCount()
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{
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return 1;
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}</pre> <pre> virtual video::SMaterial& getMaterial(u32 i)
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{
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return Material;
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}
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};</pre></td>
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</tr>
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</table>
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<p>That's it. The Scene node is done. Now we simply have to start the engine,
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create the scene node and a camera, and look at the result.</p>
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<table width="95%" border="0" cellspacing="2" cellpadding="0" bgcolor="#CCCCCC" align="center">
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<tr>
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<td> <pre>int main()<br>{
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IrrlichtDevice *device =
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createDevice(video::EDT_OPENGL, core::dimension2d<s32>(640, 480), 16, false);</pre> <pre> device->setWindowCaption(L"Custom Scene Node - Irrlicht Engine Demo");</pre> <pre> video::IVideoDriver* driver = device->getVideoDriver();
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scene::ISceneManager* smgr = device->getSceneManager();</pre>
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<pre> smgr->addCameraSceneNode(0, core::vector3df(0,-40,0), core::vector3df(0,0,0));
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</pre></td>
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</tr>
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</table>
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<p>Create our scene node. Note that it is dropped (->drop()) instantly
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after we create it. This is possible because the scene manager now takes
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care of it. This is not nessecary, it would also be possible to drop it
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at the end of the program.</p>
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<table width="95%" border="0" cellspacing="2" cellpadding="0" bgcolor="#CCCCCC" align="center">
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<tr>
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<td> <pre>CSampleSceneNode *myNode = <br> new CSampleSceneNode(smgr->getRootSceneNode(), smgr, 666);
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myNode->drop();</pre> </td>
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</tr>
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</table>
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<p>To animate something in this boring scene consisting only of one tetraeder,
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and to show, that you now can use your scene node like any other scene
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node in the engine, we add an animator to the scene node, which rotates
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the node a little bit. </p>
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<table width="95%" border="0" cellspacing="2" cellpadding="0" bgcolor="#CCCCCC" align="center">
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<tr>
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<td> <pre>scene::ISceneNodeAnimator* anim = <br> smgr->createRotationAnimator(core::vector3df(0.8f, 0, 0.8f));
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myNode->addAnimator(anim);
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anim->drop();</pre> </td>
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</tr>
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</table>
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<p>Now draw everything and finish.</p>
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<table width="95%" border="0" cellspacing="2" cellpadding="0" bgcolor="#CCCCCC" align="center">
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<tr>
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<td> <pre> while(device->run())<br> {<br> driver->beginScene(true, true, video::SColor(0,100,100,100));
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smgr->drawAll();
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driver->endScene();
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}
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device->drop();
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return 0;
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}</pre> </td>
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</tr>
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</table>
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<p>That's it. Compile and play around with the program. </p></td>
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</tr>
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</table>
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<p> </p>
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</body>
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</html>
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