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Physx Hadinitialoverlap

 2 years ago
source link: http://pkxpp.github.io/2020/11/11/PhysX-hadInitialOverlap/
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在做碰撞检测的时候，返回结果一般用hasBlock就可以知道是否碰撞了，但是发现还有一个hadInitialOverlap的时候有点疑惑。这个是啥意思？干什么用的？

hasBlock和hadInitialOverlap

  • hasBlock

在HitBuffer的PxHitCallback中

template<typename HitType>
struct PxHitCallback
{
    HitType        block;            //!< Holds the closest blocking hit result for the query. Invalid if hasBlock is false.
    bool        hasBlock;        //!< Set to true if there was a blocking hit during query.

    HitType*    touches;        //!< User specified buffer for touching hits.
  • hadInitialOverlap

在PxLocationHit结构体中

struct PxLocationHit : public PxQueryHit
{
    PX_INLINE            PxLocationHit() : flags(0), position(PxVec3(0)), normal(PxVec3(0)), distance(PX_MAX_REAL)    {}

    /**
    \note For raycast hits: true for shapes overlapping with raycast origin.
    \note For sweep hits: true for shapes overlapping at zero sweep distance.

    @see PxRaycastHit PxSweepHit
    */
    PX_INLINE bool        hadInitialOverlap() const { return (distance <= 0.0f); }

拿Sweep测试，测试代码如下

    PxSweepBuffer hitSweep;
    PxSphereGeometry sweepShape = PxSphereGeometry(30);
    PxHitFlags hitFlags = PxHitFlags(PxHitFlag::eDEFAULT);
    PxQueryFilterData filterData = PxQueryFilterData(PxQueryFlag::eSTATIC);
    status = gScene->sweep(sweepShape, t, unitDir, PxReal(0.0f), hitSweep, hitFlags, filterData);
    bool bInitOverlap = hitSweep.block.hadInitialOverlap();

通过修改半径和Sweep距离来看其中情况

情况1：初始的时候没有发生碰撞，Sweep过程中也没有发生碰撞

半径 = 30 距离 = 0

1

hitSweep.hasBlock = false
hitSweep.block.hadInitialOverlap() = false

情况2：初始的时候没有发生碰撞，Sweep过程中发生碰撞

半径 = 30 距离 = 100

2

hitSweep.hasBlock = true
hitSweep.block.hadInitialOverlap() = false

情况3：初始的时候发生碰撞，Sweep距离为0

半径 = 100 距离 = 0

3

hitSweep.hasBlock = true
hitSweep.block.hadInitialOverlap() = true

  • 1.是否碰撞用hasBlock就可以了

  • 2.有些需求如果想知道一开始就发生碰撞了的话，就用hadInitialOverlap。而且hasBlock也是生效的


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