Separate Stepper
Capostrophic
5 years ago
parent
5d625c12dc
commit
ca6cce0c7e
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#ifndef OPENMW_MWPHYSICS_CONSTANTS_H
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#define OPENMW_MWPHYSICS_CONSTANTS_H
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namespace MWPhysics
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{
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static const float sStepSizeUp = 34.0f;
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static const float sStepSizeDown = 62.0f;
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static const float sMinStep = 10.f;
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static const float sGroundOffset = 1.0f;
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static const float sMaxSlope = 49.0f;
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// Arbitrary number. To prevent infinite loops. They shouldn't happen but it's good to be prepared.
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static const int sMaxIterations = 8;
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}
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#endif
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#include "stepper.hpp"
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#include <limits>
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#include <BulletCollision/CollisionDispatch/btCollisionObject.h>
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#include <BulletCollision/CollisionDispatch/btCollisionWorld.h>
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#include "collisiontype.hpp"
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#include "constants.hpp"
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namespace MWPhysics
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{
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static bool canStepDown(const ActorTracer &stepper)
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{
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if (!stepper.mHitObject)
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return false;
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static const float sMaxSlopeCos = std::cos(osg::DegreesToRadians(sMaxSlope));
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if (stepper.mPlaneNormal.z() <= sMaxSlopeCos)
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return false;
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return stepper.mHitObject->getBroadphaseHandle()->m_collisionFilterGroup != CollisionType_Actor;
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}
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Stepper::Stepper(const btCollisionWorld *colWorld, const btCollisionObject *colObj)
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: mColWorld(colWorld)
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, mColObj(colObj)
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, mHaveMoved(true)
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{
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}
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bool Stepper::step(osg::Vec3f &position, const osg::Vec3f &toMove, float &remainingTime)
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{
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/*
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* Slide up an incline or set of stairs. Should be called only after a
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* collision detection otherwise unnecessary tracing will be performed.
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*
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* NOTE: with a small change this method can be used to step over an obstacle
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* of height sStepSize.
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*
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* If successful return 'true' and update 'position' to the new possible
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* location and adjust 'remainingTime'.
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*
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* If not successful return 'false'. May fail for these reasons:
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* - can't move directly up from current position
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* - having moved up by between epsilon() and sStepSize, can't move forward
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* - having moved forward by between epsilon() and toMove,
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* = moved down between 0 and just under sStepSize but slope was too steep, or
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* = moved the full sStepSize down (FIXME: this could be a bug)
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*
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* Starting position. Obstacle or stairs with height upto sStepSize in front.
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*
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* +--+ +--+ |XX
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* | | -------> toMove | | +--+XX
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* | | | | |XXXXX
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* | | +--+ | | +--+XXXXX
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* | | |XX| | | |XXXXXXXX
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* +--+ +--+ +--+ +--------
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* ==============================================
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*/
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/*
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* Try moving up sStepSize using stepper.
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* FIXME: does not work in case there is no front obstacle but there is one above
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*
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* +--+ +--+
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* | | | |
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* | | | | |XX
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* | | | | +--+XX
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* | | | | |XXXXX
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* +--+ +--+ +--+ +--+XXXXX
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* |XX| |XXXXXXXX
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* +--+ +--------
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* ==============================================
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*/
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if (mHaveMoved)
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{
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mHaveMoved = false;
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mUpStepper.doTrace(mColObj, position, position+osg::Vec3f(0.0f,0.0f,sStepSizeUp), mColWorld);
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if (mUpStepper.mFraction < std::numeric_limits<float>::epsilon())
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return false; // didn't even move the smallest representable amount
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// (TODO: shouldn't this be larger? Why bother with such a small amount?)
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}
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/*
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* Try moving from the elevated position using tracer.
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*
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* +--+ +--+
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* | | |YY| FIXME: collision with object YY
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* | | +--+
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* | |
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* <------------------->| |
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* +--+ +--+
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* |XX| the moved amount is toMove*tracer.mFraction
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* +--+
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* ==============================================
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*/
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osg::Vec3f tracerPos = mUpStepper.mEndPos;
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mTracer.doTrace(mColObj, tracerPos, tracerPos + toMove, mColWorld);
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if (mTracer.mFraction < std::numeric_limits<float>::epsilon())
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return false; // didn't even move the smallest representable amount
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/*
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* Try moving back down sStepSizeDown using stepper.
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* NOTE: if there is an obstacle below (e.g. stairs), we'll be "stepping up".
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* Below diagram is the case where we "stepped over" an obstacle in front.
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*
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* +--+
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* |YY|
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* +--+ +--+
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* | |
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* | |
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* +--+ | |
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* |XX| | |
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* +--+ +--+
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* ==============================================
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*/
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mDownStepper.doTrace(mColObj, mTracer.mEndPos, mTracer.mEndPos-osg::Vec3f(0.0f,0.0f,sStepSizeDown), mColWorld);
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if (!canStepDown(mDownStepper))
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{
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// Try again with increased step length
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if (mTracer.mFraction < 1.0f || toMove.length2() > sMinStep*sMinStep)
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return false;
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osg::Vec3f direction = toMove;
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direction.normalize();
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mTracer.doTrace(mColObj, tracerPos, tracerPos + direction*sMinStep, mColWorld);
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if (mTracer.mFraction < 0.001f)
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return false;
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mDownStepper.doTrace(mColObj, mTracer.mEndPos, mTracer.mEndPos-osg::Vec3f(0.0f,0.0f,sStepSizeDown), mColWorld);
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if (!canStepDown(mDownStepper))
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return false;
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}
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if (mDownStepper.mFraction < 1.0f)
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{
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// only step down onto semi-horizontal surfaces. don't step down onto the side of a house or a wall.
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// TODO: stepper.mPlaneNormal does not appear to be reliable - needs more testing
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// NOTE: caller's variables 'position' & 'remainingTime' are modified here
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position = mDownStepper.mEndPos;
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remainingTime *= (1.0f-mTracer.mFraction); // remaining time is proportional to remaining distance
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mHaveMoved = true;
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return true;
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}
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return false;
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}
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}
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@ -0,0 +1,32 @@
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#ifndef OPENMW_MWPHYSICS_STEPPER_H
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#define OPENMW_MWPHYSICS_STEPPER_H
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#include "trace.h"
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class btCollisionObject;
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class btCollisionWorld;
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namespace osg
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{
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class Vec3f;
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}
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namespace MWPhysics
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{
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class Stepper
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{
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private:
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const btCollisionWorld *mColWorld;
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const btCollisionObject *mColObj;
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ActorTracer mTracer, mUpStepper, mDownStepper;
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bool mHaveMoved;
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public:
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Stepper(const btCollisionWorld *colWorld, const btCollisionObject *colObj);
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bool step(osg::Vec3f &position, const osg::Vec3f &toMove, float &remainingTime);
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};
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}
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#endif
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