mirror of
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47ed3a3675
The bulk of this commit was generated by running:
run-clang-tidy.py \
-checks='-*,llvm-namespace-comment' \
-header-filter=^/.../mozilla-central/.* \
-fix
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 -*- */
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/* vim: set sw=2 ts=8 et tw=80 : */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_layers_AxisPhysicsModel_h
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#define mozilla_layers_AxisPhysicsModel_h
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#include "AxisPhysicsModel.h"
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#include <sys/types.h> // for int32_t
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#include "mozilla/TimeStamp.h" // for TimeDuration
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namespace mozilla {
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namespace layers {
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/**
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* AxisPhysicsModel encapsulates a generic 1-dimensional physically-based motion
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* model.
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*
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* It performs frame-rate independent interpolation and RK4 integration for
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* smooth animation with stable, deterministic behavior.
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* Implementations are expected to subclass and override the Acceleration()
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* method.
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*/
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class AxisPhysicsModel {
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public:
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AxisPhysicsModel(double aInitialPosition, double aInitialVelocity);
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~AxisPhysicsModel();
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/**
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* Advance the physics simulation.
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* |aDelta| is the time since the last sample.
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*/
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void Simulate(const TimeDuration& aDeltaTime);
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/**
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* Gets the raw velocity of this axis at this moment.
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*/
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double GetVelocity();
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/**
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* Sets the raw velocity of this axis at this moment.
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*/
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void SetVelocity(double aVelocity);
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/**
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* Gets the raw position of this axis at this moment.
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*/
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double GetPosition();
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/**
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* Sets the raw position of this axis at this moment.
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*/
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void SetPosition(double aPosition);
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protected:
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struct State
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{
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State(double ap, double av) : p(ap), v(av) {};
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double p; // Position
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double v; // Velocity
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};
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struct Derivative
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{
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Derivative() : dp(0.0), dv(0.0) {};
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Derivative(double aDp, double aDv) : dp(aDp), dv(aDv) {};
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double dp; // dp / delta time = Position
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double dv; // dv / delta time = Velocity
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};
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/**
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* Acceleration must be overridden and return the number of
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* axis-position-units / second that should be added or removed from the
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* velocity.
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*/
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virtual double Acceleration(const State &aState) = 0;
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private:
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/**
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* Duration of fixed delta time step (seconds)
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*/
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static const double kFixedTimestep;
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/**
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* 0.0 - 1.0 value indicating progress between current and next simulation
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* sample. Normalized to units of kFixedTimestep duration.
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*/
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double mProgress;
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/**
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* Sample of simulation state as it existed
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* (1.0 - mProgress) * kFixedTimestep seconds in the past.
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*/
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State mPrevState;
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/**
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* Sample of simulation state as it will be in mProgress * kFixedTimestep
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* seconds in the future.
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*/
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State mNextState;
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/**
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* Perform RK4 (Runge-Kutta method) Integration to calculate the next
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* simulation sample.
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*/
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void Integrate(double aDeltaTime);
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/**
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* Apply delta velocity and position represented by aDerivative over
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* aDeltaTime seconds, calculate new acceleration, and return new deltas.
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*/
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Derivative Evaluate(const State &aInitState, double aDeltaTime,
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const Derivative &aDerivative);
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/**
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* Helper function for performing linear interpolation (lerp) of double's
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*/
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static double LinearInterpolate(double aV1, double aV2, double aBlend);
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};
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} // namespace layers
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} // namespace mozilla
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#endif
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