Avoid warning and make local variable lower-case.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@6000 dfc29bdd-3216-0410-991c-e03cc46cb475

examples/26.OcclusionQuery/main.cpp

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+/** Example 026 OcclusionQuery
+
+This tutorial shows how to speed up rendering by use of the
+OcclusionQuery feature. The usual rendering tries to avoid rendering of
+scene nodes by culling those nodes which are outside the visible area, the
+view frustum. However, this technique does not cope with occluded objects
+which are still in the line of sight, but occluded by some larger object
+between the object and the eye (camera). Occlusion queries check exactly that.
+The queries basically measure the number of pixels that a previous render
+left on the screen.
+Since those pixels cannot be recognized at the end of a rendering anymore,
+the pixel count is measured directly when rendering. Thus, one needs to render
+the occluder (the object in front) first. This object needs to write to the
+z-buffer in order to become a real occluder. Then the node is rendered and in
+case a z-pass happens, i.e. the pixel is written to the framebuffer, the pixel
+is counted in the query.
+The result of a query is the number of pixels which got through. One can, based
+on this number, judge if the scene node is visible enough to be rendered, or if
+the node should be removed in the next round. Also note that the number of
+pixels is a safe over approximation in general. The pixels might be overdrawn
+later on, and the GPU tries to avoid inaccuracies which could lead to false
+negatives in the queries.
+
+As you might have recognized already, we had to render the node to get the
+numbers. So where's the benefit, you might say. There are several ways where
+occlusion queries can help. It is often a good idea to just render the bbox
+of the node instead of the actual mesh. This is really fast and is a safe over
+approximation. If you need a more exact render with the actual geometry, it's
+a good idea to render with just basic solid material. Avoid complex shaders
+and state changes through textures. There's no need while just doing the
+occlusion query. At least if the render is not used for the actual scene. This
+is the third way to optimize occlusion queries. Just check the queries every
+5th or 10th frame, or even less frequent. This depends on the movement speed
+of the objects and camera.
+*/
+
+#ifdef _MSC_VER
+// We'll also define this to stop MSVC complaining about sprintf().
+#define _CRT_SECURE_NO_WARNINGS
+#pragma comment(lib, "Irrlicht.lib")
+#endif
+
+#include <irrlicht.h>
+#include "driverChoice.h"
+#include "exampleHelper.h"
+
+using namespace irr;
+
+/*
+We need keyboard input events to switch some parameters
+*/
+class MyEventReceiver : public IEventReceiver
+{
+public:
+	// This is the one method that we have to implement
+	virtual bool OnEvent(const SEvent& event)
+	{
+		// Remember whether each key is down or up
+		if (event.EventType == irr::EET_KEY_INPUT_EVENT)
+			KeyIsDown[event.KeyInput.Key] = event.KeyInput.PressedDown;
+
+		return false;
+	}
+
+	// This is used to check whether a key is being held down
+	virtual bool IsKeyDown(EKEY_CODE keyCode) const
+	{
+		return KeyIsDown[keyCode];
+	}
+	
+	MyEventReceiver()
+	{
+		for (u32 i=0; i<KEY_KEY_CODES_COUNT; ++i)
+			KeyIsDown[i] = false;
+	}
+
+private:
+	// We use this array to store the current state of each key
+	bool KeyIsDown[KEY_KEY_CODES_COUNT];
+};
+
+
+/*
+We create an irr::IrrlichtDevice and the scene nodes. One occluder, one
+occluded. The latter is a complex sphere, which has many triangles.
+*/
+int main()
+{
+	// ask user for driver
+	video::E_DRIVER_TYPE driverType=driverChoiceConsole();
+	if (driverType==video::EDT_COUNT)
+		return 1;
+
+	// create device
+	MyEventReceiver receiver;
+
+	IrrlichtDevice* device = createDevice(driverType,
+			core::dimension2d<u32>(640, 480), 16, false, false, false, &receiver);
+
+	if (device == 0)
+		return 1; // could not create selected driver.
+
+	video::IVideoDriver* driver = device->getVideoDriver();
+	scene::ISceneManager* smgr = device->getSceneManager();
+
+	const io::path mediaPath = getExampleMediaPath();
+
+	smgr->getGUIEnvironment()->addStaticText(L"Press Space to hide occluder.", core::recti(10,10, 200,50));
+
+	/*
+	Create the node to be occluded. We create a sphere node with high poly count.
+	*/
+	scene::ISceneNode * node = smgr->addSphereSceneNode(10, 64);
+	if (node)
+	{
+		node->setPosition(core::vector3df(0,0,60));
+		node->setMaterialTexture(0, driver->getTexture(mediaPath + "wall.bmp"));
+		node->setMaterialFlag(video::EMF_LIGHTING, false);
+	}
+
+	/*
+	Now we create another node, the occluder. It's a simple plane.
+	*/
+	scene::ISceneNode* plane = smgr->addMeshSceneNode(smgr->addHillPlaneMesh(
+		"plane", core::dimension2df(10,10), core::dimension2du(2,2)), 0, -1,
+		core::vector3df(0,0,20), core::vector3df(270,0,0));
+
+	if (plane)
+	{
+		plane->setMaterialTexture(0, driver->getTexture(mediaPath + "t351sml.jpg"));
+		plane->setMaterialFlag(video::EMF_LIGHTING, false);
+		plane->setMaterialFlag(video::EMF_BACK_FACE_CULLING, true);
+	}
+
+	/*
+	Here we create the occlusion query. Because we don't have a plain mesh scene node
+	(ESNT_MESH or ESNT_ANIMATED_MESH), we pass the base geometry as well. Instead,
+	we could also pass a simpler mesh or the bounding box. But we will use a time
+	based method, where the occlusion query renders to the frame buffer and in case
+	of success (occlusion), the mesh is not drawn for several frames.
+	*/
+	driver->addOcclusionQuery(node, ((scene::IMeshSceneNode*)node)->getMesh());
+
+	/*
+	We have done everything, just a camera and draw it. We also write the
+	current frames per second and the name of the driver to the caption of the
+	window to examine the render speedup.
+	We also store the time for measuring the time since the last occlusion query ran
+	and store whether the node should be visible in the next frames.
+	*/
+	smgr->addCameraSceneNode();
+	int lastFPS = -1;
+	u32 timeNow = device->getTimer()->getTime();
+	bool nodeVisible=true;
+
+	while(device->run())
+	{
+		plane->setVisible(!receiver.IsKeyDown(irr::KEY_SPACE));
+
+		driver->beginScene(video::ECBF_COLOR | video::ECBF_DEPTH, video::SColor(255,113,113,133));
+		/*
+		First, we draw the scene, possibly without the occluded element. This is necessary
+		because we need the occluder to be drawn first. You can also use several scene
+		managers to collect a number of possible occluders in a separately rendered
+		scene.
+		*/
+		node->setVisible(nodeVisible);
+		smgr->drawAll();
+		smgr->getGUIEnvironment()->drawAll();
+
+		/*
+		Once in a while, here every 100 ms, we check the visibility. We run the queries,
+		update the pixel value, and query the result. Since we already rendered the node
+		we render the query invisible. The update is made blocking, as we need the result
+		immediately. If you don't need the result immediately, e.g. because you have other
+		things to render, you can call the update non-blocking. This gives the GPU more
+		time to pass back the results without flushing the render pipeline.
+		If the update was called non-blocking, the result from getOcclusionQueryResult is
+		either the previous value, or 0xffffffff if no value has been generated at all, yet.
+		The result is taken immediately as visibility flag for the node.
+		*/
+		if (device->getTimer()->getTime()-timeNow>100)
+		{
+			driver->runAllOcclusionQueries(false);
+			driver->updateAllOcclusionQueries();
+			nodeVisible=driver->getOcclusionQueryResult(node)>0;
+			timeNow=device->getTimer()->getTime();
+		}
+
+		driver->endScene();
+
+		int fps = driver->getFPS();
+
+		if (lastFPS != fps)
+		{
+			core::stringw tmp(L"OcclusionQuery Example [");
+			tmp += driver->getName();
+			tmp += L"] fps: ";
+			tmp += fps;
+
+			device->setWindowCaption(tmp.c_str());
+			lastFPS = fps;
+		}
+	}
+
+	/*
+	In the end, delete the Irrlicht device.
+	*/
+	device->drop();
+	
+	return 0;
+}
+
+/*
+That's it. Compile and play around with the program.
+**/