mirror of
https://github.com/classilla/tenfourfox.git
synced 2024-09-11 02:56:06 +00:00
132 lines
3.3 KiB
C++
132 lines
3.3 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
|
|
/* vim: set sw=2 ts=8 et tw=80 : */
|
|
/* This Source Code Form is subject to the terms of the Mozilla Public
|
|
* License, v. 2.0. If a copy of the MPL was not distributed with this
|
|
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
|
|
|
|
#ifndef mozilla_layers_AxisPhysicsModel_h
|
|
#define mozilla_layers_AxisPhysicsModel_h
|
|
|
|
#include "AxisPhysicsModel.h"
|
|
#include <sys/types.h> // for int32_t
|
|
#include "mozilla/TimeStamp.h" // for TimeDuration
|
|
|
|
namespace mozilla {
|
|
namespace layers {
|
|
|
|
|
|
/**
|
|
* AxisPhysicsModel encapsulates a generic 1-dimensional physically-based motion
|
|
* model.
|
|
*
|
|
* It performs frame-rate independent interpolation and RK4 integration for
|
|
* smooth animation with stable, deterministic behavior.
|
|
* Implementations are expected to subclass and override the Acceleration()
|
|
* method.
|
|
*/
|
|
class AxisPhysicsModel {
|
|
public:
|
|
AxisPhysicsModel(double aInitialPosition, double aInitialVelocity);
|
|
~AxisPhysicsModel();
|
|
|
|
/**
|
|
* Advance the physics simulation.
|
|
* |aDelta| is the time since the last sample.
|
|
*/
|
|
void Simulate(const TimeDuration& aDeltaTime);
|
|
|
|
/**
|
|
* Gets the raw velocity of this axis at this moment.
|
|
*/
|
|
double GetVelocity();
|
|
|
|
/**
|
|
* Sets the raw velocity of this axis at this moment.
|
|
*/
|
|
void SetVelocity(double aVelocity);
|
|
|
|
/**
|
|
* Gets the raw position of this axis at this moment.
|
|
*/
|
|
double GetPosition();
|
|
|
|
/**
|
|
* Sets the raw position of this axis at this moment.
|
|
*/
|
|
void SetPosition(double aPosition);
|
|
|
|
protected:
|
|
|
|
struct State
|
|
{
|
|
State(double ap, double av) : p(ap), v(av) {};
|
|
double p; // Position
|
|
double v; // Velocity
|
|
};
|
|
|
|
struct Derivative
|
|
{
|
|
Derivative() : dp(0.0), dv(0.0) {};
|
|
Derivative(double aDp, double aDv) : dp(aDp), dv(aDv) {};
|
|
double dp; // dp / delta time = Position
|
|
double dv; // dv / delta time = Velocity
|
|
};
|
|
|
|
/**
|
|
* Acceleration must be overridden and return the number of
|
|
* axis-position-units / second that should be added or removed from the
|
|
* velocity.
|
|
*/
|
|
virtual double Acceleration(const State &aState) = 0;
|
|
|
|
private:
|
|
|
|
/**
|
|
* Duration of fixed delta time step (seconds)
|
|
*/
|
|
static const double kFixedTimestep;
|
|
|
|
/**
|
|
* 0.0 - 1.0 value indicating progress between current and next simulation
|
|
* sample. Normalized to units of kFixedTimestep duration.
|
|
*/
|
|
double mProgress;
|
|
|
|
/**
|
|
* Sample of simulation state as it existed
|
|
* (1.0 - mProgress) * kFixedTimestep seconds in the past.
|
|
*/
|
|
State mPrevState;
|
|
|
|
/**
|
|
* Sample of simulation state as it will be in mProgress * kFixedTimestep
|
|
* seconds in the future.
|
|
*/
|
|
State mNextState;
|
|
|
|
/**
|
|
* Perform RK4 (Runge-Kutta method) Integration to calculate the next
|
|
* simulation sample.
|
|
*/
|
|
void Integrate(double aDeltaTime);
|
|
|
|
/**
|
|
* Apply delta velocity and position represented by aDerivative over
|
|
* aDeltaTime seconds, calculate new acceleration, and return new deltas.
|
|
*/
|
|
Derivative Evaluate(const State &aInitState, double aDeltaTime,
|
|
const Derivative &aDerivative);
|
|
|
|
/**
|
|
* Helper function for performing linear interpolation (lerp) of double's
|
|
*/
|
|
static double LinearInterpolate(double aV1, double aV2, double aBlend);
|
|
|
|
};
|
|
|
|
|
|
} // namespace layers
|
|
} // namespace mozilla
|
|
|
|
#endif
|