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/* -------------------------------------------------------------------------- *
* Simbody(tm) Example: Event Handler *
* -------------------------------------------------------------------------- *
* This is part of the SimTK biosimulation toolkit originating from *
* Simbios, the NIH National Center for Physics-Based Simulation of *
* Biological Structures at Stanford, funded under the NIH Roadmap for *
* Medical Research, grant U54 GM072970. See https://simtk.org/home/simbody. *
* *
* Portions copyright (c) 2008-12 Stanford University and the Authors. *
* Authors: Peter Eastman *
* Contributors: *
* *
* Licensed under the Apache License, Version 2.0 (the "License"); you may *
* not use this file except in compliance with the License. You may obtain a *
* copy of the License at http://www.apache.org/licenses/LICENSE-2.0. *
* *
* Unless required by applicable law or agreed to in writing, software *
* distributed under the License is distributed on an "AS IS" BASIS, *
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. *
* See the License for the specific language governing permissions and *
* limitations under the License. *
* -------------------------------------------------------------------------- */
/* This example demonstrates the use of an event handler to implement
discontinuous changes to the State during time stepping. */
#include "Simbody.h"
using namespace SimTK;
class BounceHandler : public TriggeredEventHandler {
public:
BounceHandler() : TriggeredEventHandler(Stage::Position) {
getTriggerInfo().setTriggerOnRisingSignTransition(false);
}
Real getValue(const State& state) const override {
return state.getQ()[0];
}
// Note: in general a discontinuous velocity change should be followed by
// an impulse-momentum analysis to ensure that momentum is conserved. We're
// not doing that here.
void handleEvent(State& state, Real accuracy, bool& shouldTerminate) const override {
state.updU()[0] *= -1;
}
};
int main() {
// Create the system.
MultibodySystem system; system.setUseUniformBackground(true);
SimbodyMatterSubsystem matter(system);
GeneralForceSubsystem forces(system);
Force::UniformGravity gravity(forces, matter, Vec3(0, -9.8, 0));
Body::Rigid pendulumBody(MassProperties(1.0, Vec3(0), Inertia(1)));
pendulumBody.addDecoration(Transform(), DecorativeSphere(0.1));
MobilizedBody::Pin pendulum(matter.updGround(), Transform(Vec3(0)), pendulumBody, Transform(Vec3(0, 1, 0)));
Visualizer viz(system);
system.addEventReporter(new Visualizer::Reporter(viz, 1./30));
system.addEventHandler(new BounceHandler());
// Initialize the system and state.
system.realizeTopology();
State state = system.getDefaultState();
pendulum.setOneU(state, 0, 1.0);
// Simulate it.
RungeKuttaMersonIntegrator integ(system);
TimeStepper ts(system, integ);
ts.initialize(state);
ts.stepTo(100.0);
}
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