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309 lines
17 KiB
HTML
309 lines
17 KiB
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<html>
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<head>
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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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</head>
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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 7. Collision detection
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and response</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>In this tutorial, I will show how to collision detection with the Irrlicht
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Engine. I will describe 3 methods: Automatic collision detection for
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moving through 3d worlds with stair climbing and sliding, manual triangle
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picking and manual scene node picking.</p>
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<p>The program which is described here will look like this:</p>
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<p align="center"><img src="../../media/007shot.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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<div align="left">
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<p>To start, we take the program from tutorial 2, which loaded and displayed
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a quake 3 level. We will use the level to walk in it and to pick triangles
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from it. In addition we'll place 3 animated models into it for scene
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node picking. The following code starts up the engine and loads a
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quake 3 level. I will not explain it, because it should already be
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known from tutorial 2.</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><font size="2"><font color="#008000">#include <irrlicht.h>
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#include <iostream><br>
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</font><b>using namespace </b>irr;
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<font color="#008000">#pragma comment(lib, "Irrlicht.lib")
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</font><b>int </b>main()
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{
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<font color="#008000"> // let user select driver type</font>
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<br> video::E_DRIVER_TYPE driverType;<br><br> printf("Please select the driver you want for this example:\n"\<br> " (a) Direct3D 9.0c\n (b) Direct3D 8.1\n (c) OpenGL 1.5\n"\<br> " (d) Software Renderer\n (e) Apfelbaum Software Renderer\n"\<br> " (f) NullDevice\n (otherKey) exit\n\n");<br><br> char i;<br> std::cin >> i;<br><br> switch(i)<br> {<br> case 'a': driverType = video::EDT_DIRECT3D9;break;<br> case 'b': driverType = video::EDT_DIRECT3D8;break;<br> case 'c': driverType = video::EDT_OPENGL; break;<br> case 'd': driverType = video::EDT_SOFTWARE; break;<br> case 'e': driverType = video::EDT_BURNINGSVIDEO;break; <br> case 'f': driverType = video::EDT_NULL; break;<br> default: return 0;<br> } <br>
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<font color="#008000"> // create device</font></font></pre>
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<pre> IrrlichtDevice *device = createDevice(driverType,
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core::dimension2d<s32>(640, 480), 16, false);<br>
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if (device == 0)<br> return 1; // could not create selected driver.<br><br> video::IVideoDriver* driver = device->getVideoDriver();<br> scene::ISceneManager* smgr = device->getSceneManager();<br><br> <font size="2">device->getFileSystem()->addZipFileArchive<br> (<font color="#FF0000">"../../media/map-20kdm2.pk3"</font>);
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scene::IAnimatedMesh* q3levelmesh = smgr->getMesh(<font color="#FF0000">"20kdm2.bsp"</font>);
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scene::ISceneNode* q3node = <font color="#800080">0</font>;
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<b>if </b>(q3levelmesh)
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q3node = smgr->addOctTreeSceneNode(q3levelmesh->getMesh(<font color="#800080">0</font>));
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</font></pre>
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</td>
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</tr>
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</table>
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<p> So far so good, we've loaded the quake 3 level like in tutorial
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2. Now, here comes something different: We create a triangle selector.
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A triangle selector is a class which can fetch the triangles from
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scene nodes for doing different things with them, for example collision
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detection. There are different triangle selectors, and all can be
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created with the ISceneManager. In this example, we create an OctTreeTriangleSelector,
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which optimizes the triangle output a little bit by reducing it like
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an octree. This is very useful for huge meshes like quake 3 levels.<br>
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Afte we created the triangle selector, we attach it to the q3node.
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This is not necessary, but in this way, we do not need to care for
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the selector, for example dropping it after we do not need it anymore.</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><font size="2">scene::ITriangleSelector* selector = <font color="#800080">0</font>;
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<b>if </b>(q3node)
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{
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q3node->setPosition(core::vector3df(-<font color="#800080">1370</font>,-<font color="#800080">130</font>,-<font color="#800080">1400</font>));
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selector = smgr->createOctTreeTriangleSelector(
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q3levelmesh->getMesh(<font color="#800080">0</font>), q3node, <font color="#800080">128</font>);
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q3node->setTriangleSelector(selector);
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}</font></pre></td>
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</tr>
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</table>
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<p> We add a first person shooter camera to the scene for being able
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to move in the quake 3 level like in tutorial 2. But this, time, we
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add a special animator to the camera: A Collision Response animator.
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This thing modifies the scene node to which it is attached to in that
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way, that it may no more move through walls and is affected by gravity.
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The only thing we have to tell the animator is how the world looks
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like, how big the scene node is, how gravity and so on. After the
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collision response animator is attached to the camera, we do not have
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to do anything more for collision detection, anything is done automaticly,
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all other collision detection code below is for picking. And please
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note another cool feature: The collsion response animator can be attached
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also to all other scene nodes, not only to cameras. And it can be
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mixed with other scene node animators. In this way, collision detection
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and response in the Irrlicht<br>
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engine is really, really easy.<br>
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Now we'll take a closer look on the parameters of createCollisionResponseAnimator().
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The first parameter is the TriangleSelector, which specifies how the
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world, against collision detection is done looks like. The second
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parameter is the scene node, which is the object, which is affected
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by collision detection, in our case it is the camera. The third defines
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how big the object is, it is the radius of an ellipsoid. Try it out
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and change the radius to smaller values, the camera will be able to
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move closer to walls after this. The next parameter is the direction
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and speed of gravity. You could set it to (0,0,0) to disable gravity.
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And the last value is just a translation: Without this, the ellipsoid
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with which collision detection is done would be around the camera,
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and the camera would be in the middle of the ellipsoid. But as human
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beings, we are used to have our eyes on top of the body, with which
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we collide with our world, not in the middle of it. So we place the
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scene node 50 units over the center of the ellipsoid with this parameter.
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And that's it, collision detection works now. <br>
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</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><font size="2"> scene::ICameraSceneNode* camera = <br> camera = smgr->addCameraSceneNodeFPS(<font color="#800080">0</font>,<font color="#800080">100.0f</font>,<font color="#800080">300.0f</font>);
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camera->setPosition(core::vector3df(-10<font color="#800080">0</font>,<font color="#800080">50</font>,-15<font color="#800080">0</font>));
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scene::ISceneNodeAnimator* anim =<br> smgr->createCollisionResponseAnimator(
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selector, camera, core::vector3df(<font color="#800080">30</font>,<font color="#800080">50</font>,<font color="#800080">30</font>),
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core::vector3df(<font color="#800080">0</font>,<font color="#800080">-3</font>,<font color="#800080">0</font>),
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core::vector3df(<font color="#800080">0</font>,<font color="#800080">50</font>,<font color="#800080">0</font>));<br>
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selector->drop();<br>
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camera->addAnimator(anim);
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anim->drop();</font></pre></td>
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</tr>
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</table>
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<p> Because collision detection is no big deal in irrlicht, I'll describe
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how to do two different types of picking in the next section. But
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before this, I'll prepare the scene a little. I need three animated
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characters which we <br>
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could pick later, a dynamic light for lighting them, a billboard for
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drawing where we found an intersection, and, yes, I need to get rid
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of this mouse cursor. :)</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><font size="2"> <font color="#0A246A"><i>// disable mouse cursor
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</i></font> device->getCursorControl()->setVisible(<b>false</b>);
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<font color="#0A246A"><i>// add billboard
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</i></font> scene::IBillboardSceneNode * bill = smgr->addBillboardSceneNode();
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bill->setMaterialType(video::EMT_TRANSPARENT_ADD_COLOR );
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bill->setMaterialTexture(<font color="#800080">0</font>, driver->getTexture(<br> <font color="#FF0000">"../../media/particle.bmp"</font>));
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bill->setMaterialFlag(video::EMF_LIGHTING, <b>false</b>);
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bill->setSize(core::dimension2d<f32>(<font color="#800080">20.0f</font>, <font color="#800080">20.0f</font>));
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<font color="#0A246A"><i>// add 3 animated faeries.
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</i></font> video::SMaterial material;
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material.Texture1 = driver->getTexture(<font color="#FF0000"><br> "../../media/faerie2.bmp"</font>);
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material.Lighting = <b>true</b>;
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scene::IAnimatedMeshSceneNode* node = <font color="#800080">0</font>;
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scene::IAnimatedMesh* faerie = smgr->getMesh(<br> <font color="#FF0000">"../../media/faerie.md2"</font>);
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<b>if </b>(faerie)
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{
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node = smgr->addAnimatedMeshSceneNode(faerie);
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node->setPosition(core::vector3df(-<font color="#800080">70</font>,<font color="#800080">0</font>,-<font color="#800080">90</font>));
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node->setMD2Animation(scene::EMAT_RUN);
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node->getMaterial(<font color="#800080">0</font>) = material;
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node = smgr->addAnimatedMeshSceneNode(faerie);
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node->setPosition(core::vector3df(-<font color="#800080">70</font>,<font color="#800080">0</font>,-<font color="#800080">30</font>));
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node->setMD2Animation(scene::EMAT_SALUTE);
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node->getMaterial(<font color="#800080">0</font>) = material;
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node = smgr->addAnimatedMeshSceneNode(faerie);
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node->setPosition(core::vector3df(-<font color="#800080">70</font>,<font color="#800080">0</font>,-<font color="#800080">60</font>));
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node->setMD2Animation(scene::EMAT_JUMP);
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node->getMaterial(<font color="#800080">0</font>) = material;
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}
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material.Texture1 = <font color="#800080">0</font>;
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material.Lighting = <b>false</b>;
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<font color="#0A246A"><i>// Add a light
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</i></font> smgr->addLightSceneNode(<font color="#800080">0</font>, core::vector3df(-<font color="#800080">60</font>,<font color="#800080">100</font>,<font color="#800080">400</font>),
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video::SColorf(<font color="#800080">1.0f</font>,<font color="#800080">1.0f</font>,<font color="#800080">1.0f</font>,<font color="#800080">1.0f</font>),
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<font color="#800080">600.0f</font>);</font></pre></td>
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</tr>
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</table>
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<p>For not making it to complicated, I'm doing picking inside the drawing
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loop. We take two pointers for storing the current and the last selected
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scene node and start the loop.</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><font size="2"> scene::ISceneNode* selectedSceneNode = <font color="#800080">0</font>;
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scene::ISceneNode* lastSelectedSceneNode = <font color="#800080">0</font>;
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<b>int </b>lastFPS = -<font color="#800080">1</font>;
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<b>while</b>(device->run())<br> <strong>if</strong> (device->isWindowActive())
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{
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driver->beginScene(<b>true</b>, <b>true</b>, <font color="#800080">0</font>);
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smgr->drawAll();</font></pre></td>
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</tr>
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</table>
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<p> After we've drawn the whole scene whit smgr->drawAll(), we'll do
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the first picking: We want to know which triangle of the world we are
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looking at. In addition, we want the exact point of the quake 3 level
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we are looking at. For this, we create a 3d line starting at the position
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of the camera and going through the lookAt-target of it. Then we ask
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the collision manager if this line collides with a triangle of the world
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stored in the triangle selector. If yes, we draw the 3d triangle and
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set the position of the billboard to the intersection point. </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><font size="2"> core::line3d<f32> line;
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line.start = camera->getPosition();
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line.end = line.start +
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(camera->getTarget() - line.start).normalize() * <font color="#800080">1000.0f</font>;
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core::vector3df intersection;
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core::triangle3df tri;
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<b>if </b>(smgr->getSceneCollisionManager()->getCollisionPoint(
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line, selector, intersection, tri))
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{
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bill->setPosition(intersection);
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driver->setTransform(video::ETS_WORLD, core::matrix4());
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driver->setMaterial(material);
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driver->draw3DTriangle(tri, video::SColor(<font color="#800080">0</font>,<font color="#800080">255</font>,<font color="#800080">0</font>,<font color="#800080">0</font>));
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}</font></pre></td>
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</tr>
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</table>
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<p> Another type of picking supported by the Irrlicht Engine is scene
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node picking based on bouding boxes. Every scene node has got a bounding
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box, and because of that, it's very fast for example to get the scene
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node which the camera looks<br>
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at. Again, we ask the collision manager for this, and if we've got a
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scene node, we highlight it by disabling Lighting in its material, if
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it is not the billboard or the quake 3 level. </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><font size="2"> selectedSceneNode = smgr->getSceneCollisionManager()->
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getSceneNodeFromCameraBB(camera);
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<b>if </b>(lastSelectedSceneNode)
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lastSelectedSceneNode->setMaterialFlag(
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video::EMF_LIGHTING, <b>true</b>);
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<b>if </b>(selectedSceneNode == q3node ||
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selectedSceneNode == bill)
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selectedSceneNode = <font color="#800080">0</font>;
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<b>if </b>(selectedSceneNode)
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selectedSceneNode->setMaterialFlag(
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video::EMF_LIGHTING, <b>false</b>);
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lastSelectedSceneNode = selectedSceneNode;</font></pre></td>
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</tr>
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|
</table>
|
||
|
|
<p> That's it, we just have to finish drawing.</p>
|
||
|
|
<table width="95%" border="0" cellspacing="2" cellpadding="0" bgcolor="#CCCCCC" align="center">
|
||
|
|
<tr>
|
||
|
|
<td> <pre><font size="2"> driver->endScene();
|
||
|
|
|
||
|
|
<b>int </b>fps = driver->getFPS();
|
||
|
|
|
||
|
|
<b>if </b>(lastFPS != fps)
|
||
|
|
{
|
||
|
|
core::stringw str = L"Collision detection example - Irrlicht Engine [";<br> str += driver->getName();<br> str += "] FPS:";<br> str += fps;<br><br> device->setWindowCaption(str.c_str());<br> lastFPS = fps;<br> }
|
||
|
|
}
|
||
|
|
|
||
|
|
device->drop();
|
||
|
|
|
||
|
|
<b>return </b><font color="#800080">0</font>;
|
||
|
|
}
|
||
|
|
|
||
|
|
</font></pre></td>
|
||
|
|
</tr>
|
||
|
|
</table>
|
||
|
|
<p> </p>
|
||
|
|
<p> </p>
|
||
|
|
</div>
|
||
|
|
</td>
|
||
|
|
</tr>
|
||
|
|
</table>
|
||
|
|
<p> </p>
|
||
|
|
</body>
|
||
|
|
</html>
|