RP412PHYSICSHZ names a rate and the simulation advances in whole steps of exactly that size on every machine, whatever the display does. 0 - the default, and the shipped behaviour until the play testers have spoken - is the game as it has always run: the step is however long the last frame took, which makes the frame rate part of the physics. Measured over two seconds of free fall, a 30 fps machine's pod fell three times further than a 144 fps machine's. Two players on the same track were not in the same gravity. With a rate set, the same race is bit-identical across frame rates: 30, 60 and 144 fps produce the same trajectory to the last printed digit, and identical runs reproduce exactly - which was never true of this engine before, at any frame rate. It took three pieces, and every one was found by measuring, not by reading: - Simulation::PerformTo turns lastPerformance into the accumulator it always secretly was: whole steps while time remains, the remainder carried to the next frame. Watchers and update records stay once per frame - stepping is physics, watching is I/O. - Entity::PerformAndWatch interleaves subsystems and entity per STEP. The frame loop ran all subsystems to the frame boundary and then the entity, indistinguishable from correct at one step per frame - which is why thirty years of code never noticed - and wrong at two: the thrusters raycast twice from a vehicle that had not moved, and the hover spring fired twice on one stale height sample. The subsystems are also snapped onto their entity's step grid; each Simulation anchors its grid at its own creation time, a per-run phase no seed could pin. - Mover::BeginStep clears the force accumulator per step. It was cleared once per frame while the thrusters ADD per step, so step two of a frame integrated step one's thrust again - and how many steps a frame holds rides on wall-clock jitter, which is why identical configs measured a quarter-metre apart. The quaternion renormalise counts steps now too, for the same reason. The catch-up clamp is a quarter second of simulation whatever the rate, so a machine that cannot keep up slows down rather than seizing, and does so identically everywhere. The engine's clock counts milliseconds, so rates that do not divide 1000 - 60 among them - quietly run at the neighbouring millisecond step; the log now says so and names the exact ones. 25, 50 and 100 are exact, and all three are verified bit-identical across frame rates and across runs. Verified for a single vehicle settling under gravity and hover. Driving, collisions and the network are the next frontiers, in that order: the collision path writes the victim's state with wall-clock stamps and a hard-coded 0.1 s bounce, which single-player survives and lockstep will not. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
472 lines
9.9 KiB
C++
472 lines
9.9 KiB
C++
#pragma once
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#include "entity.h"
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#include "motion.h"
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class Mover__SharedData;
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class Mover;
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class CollisionAssistant;
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class BoundingBoxTreeNode;
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class BoxedSolid;
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class BoxedSolidCollision;
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class BoxedSolidCollisionList;
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class Normal;
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class Line;
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class Environment;
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//##########################################################################
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//#################### Mover::UpdateMessage ##########################
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//##########################################################################
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struct Mover__UpdateRecord:
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public Entity::UpdateRecord
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{
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public:
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Motion
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localVelocity,
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localAcceleration;
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Vector3D
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worldLinearVelocity,
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worldLinearAcceleration;
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};
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//##########################################################################
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//##################### Mover::MakeMessage ##########################
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//##########################################################################
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class Mover__MakeMessage:
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public Entity::MakeMessage
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{
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public:
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Motion
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localVelocity,
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localAcceleration;
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Mover__MakeMessage(
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Receiver::MessageID message_ID,
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size_t length,
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Entity::ClassID class_ID,
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const EntityID &owner_ID,
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ResourceDescription::ResourceID resource_ID,
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LWord instance_flags,
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const Origin &origin,
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const Motion &velocity,
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const Motion &acceleration
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):
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Entity::MakeMessage(
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message_ID,
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length,
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class_ID,
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owner_ID,
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resource_ID,
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instance_flags,
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origin
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),
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localVelocity(velocity),
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localAcceleration(acceleration)
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{}
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Mover__MakeMessage(
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Receiver::MessageID message_ID,
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size_t length,
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const EntityID &entity_ID,
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Entity::ClassID class_ID,
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const EntityID &owner_ID,
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ResourceDescription::ResourceID resource_ID,
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LWord instance_flags,
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const Origin &origin,
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const Motion &velocity,
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const Motion &acceleration
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):
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Entity::MakeMessage(
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message_ID,
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length,
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entity_ID,
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class_ID,
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owner_ID,
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resource_ID,
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instance_flags,
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origin
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),
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localVelocity(velocity),
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localAcceleration(acceleration)
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{}
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};
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//##########################################################################
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//##################### Mover::ModelResource #########################
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//##########################################################################
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struct Mover__ModelResource
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{
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Scalar moverMass;
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Vector3D
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momentOfInertia,
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positiveLinearDragCoefficients,
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negativeLinearDragCoefficients,
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angularDragCoefficients;
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Scalar
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frictionCoefficient,
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elasticityCoefficient,
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minimumBounceSpeed;
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};
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//##########################################################################
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//############################ Mover #################################
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//##########################################################################
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class Mover:
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public Entity
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{
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//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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// Shared Data support
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//
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public:
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static Derivation *GetClassDerivations();
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static SharedData DefaultData;
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//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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// Attribute Support
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//
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public:
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enum {
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LocalVelocityAttributeID = Entity::NextAttributeID,
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LocalAccelerationAttributeID,
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WorldLinearVelocityAttributeID,
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WorldLinearAccelerationAttributeID,
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MoverMassAttributeID,
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MomentOfInertiaAttributeID,
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PositiveLinearDragCoefficientsAttributeID,
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NegativeLinearDragCoefficientsAttributeID,
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AngularDragCoefficientsAttributeID,
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FrictionCoefficientAttributeID,
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ElasticityCoefficientAttributeID,
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MinimumBounceSpeedAttributeID,
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NextAttributeID
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};
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private:
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static const IndexEntry AttributePointers[];
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protected:
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//static AttributeIndexSet AttributeIndex
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static AttributeIndexSet& GetAttributeIndex();
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//
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// public attribute declarations go here
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//
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public:
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Motion
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localVelocity,
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localAcceleration;
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Vector3D
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worldLinearVelocity,
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worldLinearAcceleration;
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Scalar moverMass;
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Vector3D
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momentOfInertia,
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positiveLinearDragCoefficients,
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negativeLinearDragCoefficients,
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angularDragCoefficients;
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Scalar
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frictionCoefficient,
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elasticityCoefficient,
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minimumBounceSpeed;
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//
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// virtual access
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//
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public:
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virtual Vector3D
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GetWorldLinearVelocity()
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{return worldLinearVelocity;}
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virtual Vector3D
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GetWorldLinearAcceleration()
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{return worldLinearAcceleration;}
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//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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// Model Support
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//
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public:
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enum {
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StasisState = Entity::StateCount,
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StateCount
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};
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typedef Mover__UpdateRecord UpdateRecord;
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typedef Mover__MakeMessage MakeMessage;
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typedef void
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(Mover::*Performance)(Scalar time_slice);
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void
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SetPerformance(Performance performance)
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{
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Check(this);
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activePerformance = (Simulation::Performance)performance;
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}
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void
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UpdateWorldMotion();
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void
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UpdateLocalMotion();
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void
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ApplyWorldAccelerations(Scalar time_slice);
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void
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ApplyAirResistanceAndGravity(Scalar power=1.0f);
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void
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CalculateDrag(
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Vector3D *drag,
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const Vector3D &velocity,
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const Vector3D &positive_CODs,
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const Vector3D &negative_CODs,
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Scalar power
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);
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void
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ApplyLocalForce(
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const Vector3D &force,
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const Vector3D &moment
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);
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void
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ApplyLocalAcceleration(
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const Vector3D &acceleration,
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const Vector3D &moment
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);
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Environment*
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GetEnvironment()
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{Check(this); return localEnvironment;}
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typedef Logical (Mover::*DeadReckoner)();
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void
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SetDeadReckoner(DeadReckoner reckoner)
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{Check(this); deadReckoner = reckoner;}
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Logical
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NoDeadReckoner();
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Logical
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LinearDeadReckoner();
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Logical
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AcceleratedDeadReckoner();
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void
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DeadReckon(Scalar time_slice);
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protected:
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void
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WriteUpdateRecord(
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Simulation::UpdateRecord *message,
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int update_model
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);
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void
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ReadUpdateRecord(Simulation::UpdateRecord *message);
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void
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PerformAndWatch(
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const Time& till,
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MemoryStream *update_stream
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);
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//
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// Per-step set-up under fixed stepping: clears the force accumulator
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// the thrusters add into, so each step integrates only its own
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// forces. See the definition for the frame-jitter bug this closes.
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//
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void
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BeginStep();
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int
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normalizeCount;
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Environment
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*localEnvironment;
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DeadReckoner
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deadReckoner;
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Origin
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projectedOrigin,
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previousOrigin;
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Motion
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projectedVelocity,
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updateAcceleration,
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updateVelocity;
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Time
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nextUpdate;
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//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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// Collision support
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//
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public:
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virtual void
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MoveCollisionVolume();
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BoundingBoxTreeNode*
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GetMoverCollisionRoot()
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{Check(this); return containedByNode;}
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BoxedSolidCollisionList*
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AllocateCollisionList();
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BoxedSolidCollisionList*
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GetCurrentCollisions(BoxedSolidCollisionList *list=NULL);
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BoxedSolid*
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FindBoxedSolidHitBy(
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Line *line,
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Entity *except_by
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);
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BoxedSolidCollisionList*
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CollideCenterOfMotion(
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Line *line,
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BoxedSolidCollisionList *list
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);
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void
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ProcessCollisionList(
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BoxedSolidCollisionList *collisions,
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Scalar time_slice,
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const Point3D &old_position,
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Damage *damage
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);
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Scalar
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StaticBounce(
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const Point3D &old_position,
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Scalar delta_t,
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Scalar penetration,
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const Normal &normal,
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Scalar *elasticity,
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Scalar bounce_min,
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Scalar *friction
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);
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Scalar
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DynamicBounce(
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Mover *other,
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Scalar delta_t,
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Scalar penetration,
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const Normal &normal,
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Scalar *elasticity
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);
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BoxedSolid*
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GetCollisionVolume()
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{Check(this); return collisionVolume;}
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BoxedSolid*
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GetCollisionTemplate()
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{Check(this); return collisionTemplate;}
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int
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GetCollisionVolumeCount()
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{Check(this); return collisionVolumeCount;}
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virtual void
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StartCollisionAssistant();
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protected:
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int collisionVolumeCount;
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BoxedSolid
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*collisionVolume,
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*collisionTemplate;
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BoundingBoxTreeNode *containedByNode;
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BoxedSolidCollisionList
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*collisionLists,
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*lastCollisionList;
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CollisionAssistant *collisionAssistant;
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virtual void
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ProcessCollision(
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Scalar time_slice,
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BoxedSolidCollision &collision,
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const Point3D &old_position,
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Damage *damage
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);
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void
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CheckAgainstBoxedSolidChain(
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BoxedSolidCollisionList *collisions,
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BoxedSolid *chain
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);
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public:
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void
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CheckVolumeAgainstBoxedSolidChain(
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BoxedSolidCollisionList *collisions,
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BoxedSolid *chain
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);
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protected:
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BoxedSolid*
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CheckLineAgainstBoxedSolidChain(
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Line *line,
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BoxedSolid *chain
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);
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//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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// Flag Support
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//
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public:
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enum {
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NoCollisionVolumeBit = Entity::NextBit,
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NoCollisionTestBit,
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InitialStasisBit,
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NextBit
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};
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enum {
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NoCollisionVolumeFlag = 1<<NoCollisionVolumeBit,
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NoCollisionTestFlag = 1<<NoCollisionTestBit,
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InitialStasisFlag = 1<<InitialStasisBit,
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DefaultFlags = DynamicFlag|MasterInstance
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};
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void
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NoCollisionVolume()
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{Check(this); simulationFlags |= NoCollisionVolumeFlag;}
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void
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SetCollisionVolume()
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{Check(this); simulationFlags &= ~NoCollisionVolumeFlag;}
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Logical
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IsCollisionVolume()
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{Check(this); return (simulationFlags&NoCollisionVolumeFlag) == 0;}
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void
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NoCollisionTest()
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{Check(this); simulationFlags |= NoCollisionTestFlag;}
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void
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SetCollisionTest()
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{Check(this); simulationFlags &= ~NoCollisionTestFlag;}
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Logical
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IsCollisionTestable()
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{Check(this); return (simulationFlags&NoCollisionTestFlag) == 0;}
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Logical
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IsInitialStasis()
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{Check(this); return (simulationFlags&InitialStasisFlag) != 0;}
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//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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// Construction and Destruction
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//
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public:
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typedef Mover__ModelResource ModelResource;
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static Mover*
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Make(MakeMessage *creation_message);
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//
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// Warning... This function requires a properly set up strtok!!!!
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//
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static Logical
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CreateMakeMessage(
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MakeMessage *creation_message,
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NotationFile *model_file,
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const ResourceDirectories *directories
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);
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static ResourceDescription::ResourceID
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CreateModelResource(
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ResourceFile *resource_file,
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const char* model_name,
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NotationFile *model_file,
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const ResourceDirectories *directories,
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ModelResource* model = NULL
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);
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Mover(
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MakeMessage *creation_message,
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SharedData &virtual_data
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);
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~Mover();
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Logical
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TestInstance() const;
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};
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