NxOgre缓冲摄像机(及摄像机抖动解决办法) (转载)

重新对摄像机进行了封装,增加了缓冲功能,使赛车的操作真实感提升了不少,关于缓冲摄像机可以参考Ogre wiki上的第三人称摄像机那篇文章

其原理是:                 使用两个SceneNode, 一个绑定摄像机,另一个用来绑定代表赛车的节点, 赛车移动的时候   摄像机的位置始终以一定速度向赛车节点靠近，这个速度跟摄像机与赛车子节点的全局坐标距离成正比.   并不断跟新两节点位置.

关于摄像机更新抖动的问题,NxOgre和Ogre使用两个不同的FrameListener来更新场景,可能会使帧更新一致,我的解决办法是在创建NxOgre::Scene的时候将 mProcessingPriority = NxOgre::Enums::Priority_Low设置成最低优先级,即不对场景进行处理(默认情况下为Priority_Medium),之后再手动更新场景 mScene->advance(timeSinceLastFrame * 0.015, NxOgre::Enums::Priority_Low);

1. //创建场景,并设置场景基本属性
2. NxOgre::SceneDescription desc;
3. //设置重力
4. desc.mGravity = NxOgre::Vec3(0.0f, -9.8f, 0.0f);
5. desc.mName = "Racing World";
6. desc.mProcessingPriority = NxOgre::Enums::Priority_Low;
7. mScene = mWorld->createScene(desc);

摄像机的封装

1. #ifndef __VEHICLECAMERA_H__
2. #define __VEHICLECAMERA_H__
3. #include <Ogre.h>
4. #include <string>
5. #include "Util.h"
6. class VehicleCamera
7. {
8. public:
9. VehicleCamera(const std::string &playerName);
10. ~VehicleCamera();
11. // 设置摄像机缓冲程度值越大越硬,越小越柔和
12. void setTightness ( Real tightness );
13. float getTightness ( )const;
14. // 设定绑定节点, cameraNode为赛车上摄像机位置的节点, lookAtNode为赛车上车体的节点
15. void setTarget ( Ogre::SceneNode* cameraNode,Ogre::SceneNode* lookAtNode );
16. // 手动更新节点位置, 与赛车同步
17. void instantUpdate ( );
18. void update (float timeSinceLastFrame );
19. private:
20. Ogre::SceneNode *mBaseCamerNode;
21. Ogre::SceneNode *mBaseLookedAtNode;
22. Ogre::SceneNode *mCameraLookAtNode;
23. Ogre::SceneNode *mCameraNode;
24. Ogre::Camera *mCamera;
25. // 设置摄像机缓冲程度值越大越硬,越小越柔和
26. float mTightness;
27. };
28. #endif

1. #include "VehicleCamera.h"
2. VehicleCamera::VehicleCamera(const std::string &playerName) :
3.                mTightness(2.0),
4.                mCameraNode(0),
5.                mCameraLookAtNode(0),
6.                mBaseLookedAtNode(0),
7.                mBaseCamerNode(0)
8. {
9.     Ogre::SceneManager* sceneMgr = Util::getSceneManager();
10.     mCamera = Util::getSceneManager()->createCamera(playerName +"VehicleCamera");
11.     mCamera->setNearClipDistance ( 0.1f );
12.     Util::removeAllViewports();
13.     Ogre::Viewport*viewport = Util::addViewport(mCamera);
14.     mCamera->setAspectRatio(Real(viewport->getActualWidth()) /
15.        Real(viewport->getActualHeight()));
16.     // 构造绑定摄像机的节点
17.     mCameraNode = sceneMgr->getRootSceneNode ()->createChildSceneNode ();
18.     mCameraLookAtNode = sceneMgr->getRootSceneNode ()->createChildSceneNode ();
19.     // 使绑定摄像机的节点自动追踪赛车节点
20.     mCameraNode->setAutoTracking ( true, mCameraLookAtNode );
21.     // [重要]设置只能延Y轴旋转,
22.     mCameraNode->setFixedYawAxis ( true );       
23.     mCameraNode->attachObject ( mCamera );
24.     // 开启N02加速模糊
25.     Util::addCompositor(viewport, "Bloom");
26.     Util::setCompositorEnabled(viewport,"Bloom",true);
27. }
28. VehicleCamera::~VehicleCamera()
29. {
30.     mCameraNode->detachAllObjects ();
31.     Util::removeAllViewports();
32.     Util::getSceneManager()->destroyCamera(mCamera);
33.     Util::getSceneManager()->destroySceneNode ( mCameraNode );
34.     Util::getSceneManager()->destroySceneNode ( mCameraLookAtNode );
35.     mCamera = 0;
36. }
37. void VehicleCamera::setTightness ( Real tightness )
38. {
39.     mTightness = tightness;
40. }
41. float VehicleCamera::getTightness ( )const
42. {
43.     return mTightness;
44. }
45. // 设定绑定节点, cameraNode为赛车上摄像机位置的节点, lookAtNode为赛车上车体的节点
46. void VehicleCamera::setTarget ( Ogre::SceneNode* cameraNode,
47.                                Ogre::SceneNode* lookAtNode )
48. {
49.     mBaseCamerNode = cameraNode;
50.     mBaseLookedAtNode = lookAtNode;
51.     instantUpdate ( );
52. }
53. // 手动更新节点位置, 与赛车同步
54. void VehicleCamera::instantUpdate ( )
55. {
56.     mCameraNode->setPosition ( mBaseCamerNode->_getDerivedPosition() );
57.     mCameraLookAtNode->setPosition ( mBaseLookedAtNode->_getDerivedPosition() );
58. }
59. void VehicleCamera::update (float timeSinceLastFrame )
60. {
61.     if (mCameraNode)
62.     {
63.         Ogre::Vector3 displacement;
64.         float rate = mTightness * timeSinceLastFrame;
65.         displacement = ( mBaseCamerNode->_getDerivedPosition() -
66.                          mCameraNode->_getDerivedPosition() );
67.         mCameraNode->translate ( displacement  * rate);
68.         displacement = ( mBaseLookedAtNode->_getDerivedPosition() -
69.                          mCameraLookAtNode->_getDerivedPosition() );
70.         mCameraLookAtNode->translate ( displacement  * rate);
71.     }
72. }