《Unity虚拟现实技术及其应用》 课件 8 physics

Physics描述游戏对象的基本物理过程，加速运动，碰撞等物理组件RigidbodyColliderCharacterControllerJointConstantForce添加物理组件Rigidbody与添加相机组件和代码组件一样的过程….Rigidbody组件的基本参数：MassThemassoftheobject(inkilogramsbydefault)DragHowmuchairresistanceaffectstheobjectwhenmovingfromforces.0meansnoairresistance,andinfinitymakestheobjectstopmovingimmediately.AngularDragUsedforrotationIsKinematicIfenabled,theobjectwillnotbedrivenbythephysicsengine,andcanonlybemanipulatedbyitsTransform.ThisisusefulformovingplatformsorifyouwanttoanimateaRigidbodythathasaHingeJointattached.Interpolate

TryoneoftheoptionsonlyifyouareseeingjerkinessinyourRigidbody’smovement-None

NoInterpolation

isapplied.-Interpolate

TransformissmoothedbasedontheTransformofthepreviousframe.-Extrapolate

TransformissmoothedbasedontheestimatedTransformofthenextframe.CollisionDetection

Usedtopreventfastmovingobjectsfrompassingthroughotherobjectswithoutdetectingcollisions.-Discrete

UseDiscretecollisiondetectionagainstallothercollidersinthescene.Usedfornormalcollisions(Thisisthedefaultvalue).-Continuous

Thishasabigimpactonphysicsperformance,leaveitsettoDiscrete,ifyoudon’thaveissueswithcollisionsoffastobjects.ConstraintsRestrictionsontheRigidbody’smotion-FreezePosition

StopstheRigidbodymovingintheworldX,YandZaxesselectively.-FreezeRotation

StopstheRigidbodyrotatingaroundthelocalX,YandZaxesselectively.notesManipulatingyourGameObjectsbyaddingforcestoaRigidbodycreatesaverydifferentfeelandlookthanadjustingtheTransformComponentdirectly.Generally,youshouldn’tmanipulatetheRigidbodyandtheTransformofthesameGameObject-onlyoneortheother.ThebiggestdifferencebetweenmanipulatingtheTransformversustheRigidbodyistheuseofforces.ScriptingforRigidbodyphysicsgameObject.GetComponent<Rigidbody>();FunctionsofRigidbody.publicvoidAddForce(Vector3force,ForceModemode=ForceMode.Force);

ForceMode:Acceleration,ignoringitsmassForce,usingitsmassImpulse,usingitsmassVelocityChange,ignoringitsmassSeeexample...publicvoidAddTorque(Vector3torque,ForceModemode=ForceMode.Force);

Addsatorquetotherigidbody.Forcecanbeappliedonlytoanactiverigidbody.IfaGameObjectisinactive,AddTorquehasnoeffect.

Seeexample...publicvoidAddForceAtPosition(Vector3force,Vector3position,ForceModemode=ForceMode.Force);Appliesforceatposition.Asaresultthiswillapplyatorqueandforceontheobject.publicvoidAddRelativeForce(Vector3force,ForceModemode=ForceMode.Force);Addsaforcetotherigidbodyrelativetoitslocalcoordinatesystem.Seeexample…andcompareAddForce()….publicvoidAddRelativeTorque(Vector3torque,ForceModemode=ForceMode.Force);voidSetDensity():Setsthemassbasedontheattachedcollidersassumingaconstantdensity.MessagesOnCollisionEnterOnCollisionEnteriscalledwhenthiscollider/rigidbodyhasbeguntouchinganotherrigidbody/collider.OnCollisionExitOnCollisionEnteriscalledwhenthiscollider/rigidbodyhasstoppedtouchinganotherrigidbody/collider.OnCollisionStayOnCollisionStayiscalledonceperframeforeverycollider/rigidbodythatistouchingrigidbody/collider.Problem7Simulateshooting:clickthekey“Space”,theballintheFiguremoveswithaninitialvelocityunderthegravity.Comparethesituationwithandwithoutairfriction.Collidercomponent

模拟物体之间相互的碰撞效应。BoxCollider盒子碰撞器,SphereCollider球体碰撞器,CapsuleCollider胶囊碰撞器,MeshCollider网格碰撞器,TerrainCollider地形碰撞器.PropertiesofCollidergameObjectThegameobjectthiscomponentisattachedto.Acomponentisalwaysattachedtoagameobject.tagThetagofthisgameobject.transformTheTransformattachedtothisGameObject.hideFlagsShouldtheobjectbehidden,savedwiththeSceneormodifiablebytheuser?nameThenameoftheobject.publicstatic

Vector3

ClosestPoint(Vector3

point,Collider

collider,

Vector3

position,

Quaternion

rotation);public

Vector3

ClosestPointOnBounds(Vector3

position);publicclassExampleClass:MonoBehaviour

{publicfloathitPoints=100.0F;publicCollidercoll;voidStart(){coll=GetComponent<Collider>();}

voidApplyHitPoints(Vector3explosionPos,floatradius){Vector3

closestPoint=coll.ClosestPointOnBounds(explosionPos);floatdistance=Vector3.Distance(closestPoint,explosionPos);

//Thedamageshoulddecreasewithdistancefromtheexplosion.floatdamage=1.0F-Mathf.Clamp01(distance/radius);hitPoints-=damage*10.0F;

}}publicstaticbool

Raycast(Vector3

origin,

Vector3

direction,

float

maxDistance

=Mathf.Infinity,int

layerMask

=DefaultRaycastLayers,

QueryTriggerInteraction

queryTriggerInteraction

=QueryTriggerInteraction.UseGlobal);publicstaticbool

Raycast(Vector3

origin,

Vector3

direction,out

RaycastHit

hitInfo,float

maxDistance,int

layerMask,

QueryTriggerInteraction

queryTriggerInteraction);CollisionDescribesacollision.CollisioninformationispassedtoCollider.OnCollisionEnter,Collider.OnCollisionStayCollider.OnCollisionExit.voidOnCollisionEnter(Collisioncol){}PropertiesofCollisioncolliderTheColliderwehit(ReadOnly).contactsThecontactpointsgeneratedbythephysicsengine.gameObjectTheGameObjectwhosecollideryouarecollidingwith.(ReadOnly).impulseThetotalimpulseappliedtothiscontactpairtoresolvethecollision.relativeVelocityTherelativelinearvelocityofthetwocollidingobjects(ReadOnly).rigidbodyTheRigidbodywehit(ReadOnly).Thisisnulliftheobjectwehitisacolliderwithnorigidbodyattached.transformTheTransformoftheobjectwehit(ReadOnly).voidOnCollisionEnter(Collisioncollision)

{foreach(ContactPointcontactincollision.contacts){Debug.DrawRay(contact.point,contact.normal,

Color.white);}if(collision.relativeVelocity.magnitude>2)audioSource.Play();}碰撞反射Collider的基本使用方法给游戏对象添加相应的Collider组件。相互碰撞的两个物体都需要添加Collder组件。IftheobjectwiththeColliderneedstobemovedduringgameplaythenyoushouldalsoattachaRigidbodycomponenttotheobject.Seeexample….comparethesituationswithandwithoutRigidbodycomponentwhenweusecolliders.PhysicMaterial用于描述物体表面物理材质的组件，模拟光滑平面上的摩擦、粗糙平面上的摩擦、刚性物体之间的碰撞、软性物体之间的碰撞。包括DynamicFriction动摩擦力、StaticFriction、Bounciness反作用力等。Createanewphysicsmaterialassets->create->physicmaterialdragthephysicsmaterialontothematerialslot.Seeexample…(themovementofobjectsonatiltedplane)Simulatethecollisionbetweentwoobjectswithdifferentphysicalmaterial.(basedonthescenetheexamplepresentedabove)Problem8Seethescene:collision_sphere_wallUnityPhysicsDongfengLiuSchoolofInformationEngineering,GDUTIntroductiontoUnityPhysicsBasicIssuesforPhysicsEngineIntegrationtodescribetheobject’sphysicalpropertiesinadatastructure,suchasmass,currentvelocity,currentposition,orientation,theexternalforces.CollisiondetectionInmostinteractivedevelopments,however,wedon’twanttheobjectstopassthrougheachother.Weneedtoknowthattwoobjectsarecolliding!Andweshouldcollectadditionalcollisioninformation.CollisionresolutionWhatwillhappenafterthecollision?Physicsengineshouldcoverthebasicsofallphysicscomponents.Everysimulationsuitableforinteractivedevelopmentwillhavethesecomponents.Built-inPhysicscomponentsinUnity3DUnity3Dembedsastate-of-the-artPhysicsengine,PhysX.Ode,TheRigidbodycomponentinUnity3Dismostlytargetedatrigidobjects.Byadjustingobject’sparametersettings,wecanmakePhysicsapproximationsinarealisticway.UnityhastwoseparatePhysicsengines:onefor3Dphysics,andonefor2Dphysics.RigidbodiesARigidbodycomponenttakesthemovementoftheobjecttowhichitisattached.weshouldn’ttrytomoveitbychangingthetransformpositionandrotationinascript.Instead,wecanapplyforcestopushtheobjectandletthePhysicsenginecalculatetheresults.KinematicmotionandRigidbodies.CollidersStaticcolliders,ColliderscanbeaddedtoanobjectwithoutaRigidbodycomponentinordertocreatefloors,walls,andsoon.Thesearereferredtoasstaticcolliders.DynamiccollidersPhysicMaterialsAsthecollidersinteract,weneedtosimulatethepropertiesofthematerialthattheyaresupposedtorepresent.WecanconfigurethefrictionandbounceusingPhysicMaterials.JointsWecanattachoneRigidbodyobjecttoanotherortoafixedpointinspaceusingajointcomponent.SpringJoint,HingeJoint,FixedJoint,CharacterJoint.CharacterControllerAcharacterinafirst-orthird-persongamewilloftenneedsomecollision-basedPhysicssothatcharacterdoesn’tfallonthefloororwalkoverthewalls.Unity3Dprovidesacomponenttocreatethisbehavior,whichiscalledCharacterController.ThiscomponentusesaCapsuleCollider.UsingCollidersPrimitivecollidersandtheirimplementationNonprimitivecollidersandtheirimplementationsUsesofTriggerCollidersEditingPolygonCollider2DPrimitive