void testForce() { System system; system.addParticle(1.0); system.addParticle(1.0); system.addParticle(1.0); VerletIntegrator integrator(0.01); CustomExternalForce* forceField = new CustomExternalForce("scale*(x+yscale*(y-y0)^2)"); forceField->addPerParticleParameter("y0"); forceField->addPerParticleParameter("yscale"); forceField->addGlobalParameter("scale", 0.5); vector<double> parameters(2); parameters[0] = 0.5; parameters[1] = 2.0; forceField->addParticle(0, parameters); parameters[0] = 1.5; parameters[1] = 3.0; forceField->addParticle(2, parameters); system.addForce(forceField); Context context(system, integrator, platform); vector<Vec3> positions(3); positions[0] = Vec3(0, 2, 0); positions[1] = Vec3(0, 0, 1); positions[2] = Vec3(1, 0, 1); context.setPositions(positions); State state = context.getState(State::Forces | State::Energy); { const vector<Vec3>& forces = state.getForces(); ASSERT_EQUAL_VEC(Vec3(-0.5, -0.5*2.0*2.0*1.5, 0), forces[0], TOL); ASSERT_EQUAL_VEC(Vec3(0, 0, 0), forces[1], TOL); ASSERT_EQUAL_VEC(Vec3(-0.5, 0.5*3.0*2.0*1.5, 0), forces[2], TOL); ASSERT_EQUAL_TOL(0.5*(1.0 + 2.0*1.5*1.5 + 3.0*1.5*1.5), state.getPotentialEnergy(), TOL); } // Try changing the parameters and make sure it's still correct. parameters[0] = 1.4; parameters[1] = 3.5; forceField->setParticleParameters(1, 2, parameters); forceField->updateParametersInContext(context); state = context.getState(State::Forces | State::Energy); { const vector<Vec3>& forces = state.getForces(); ASSERT_EQUAL_VEC(Vec3(-0.5, -0.5*2.0*2.0*1.5, 0), forces[0], TOL); ASSERT_EQUAL_VEC(Vec3(0, 0, 0), forces[1], TOL); ASSERT_EQUAL_VEC(Vec3(-0.5, 0.5*3.5*2.0*1.4, 0), forces[2], TOL); ASSERT_EQUAL_TOL(0.5*(1.0 + 2.0*1.5*1.5 + 3.5*1.4*1.4), state.getPotentialEnergy(), TOL); } }