[TOC]
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); }
测试
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
- 参数
半径 = 30 距离 = 0
- PVD图
- 结果
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
- 参数
半径 = 30 距离 = 100
- PVD图
- 结果
hitSweep.hasBlock = true
hitSweep.block.hadInitialOverlap() = false
情况3：初始的时候发生碰撞，Sweep距离为0
- 参数
半径 = 100 距离 = 0
- PVD图
- 结果
hitSweep.hasBlock = true
hitSweep.block.hadInitialOverlap() = true
总结
-
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