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/* -------------------------------------------------------------------------- *
* Simbody(tm): SimTKmath *
* -------------------------------------------------------------------------- *
* 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) 2006-17 Stanford University and the Authors. *
* Authors: Chris Dembia *
* 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. *
* -------------------------------------------------------------------------- */
#include "SimTKmath.h"
using namespace SimTK;
void testSerialChain() {
MultibodyGraphMaker mbgraph;
mbgraph.addJointType("pin", 1);
double nonzeroMass = 1.8;
mbgraph.addBody("ground", 0, false);
mbgraph.addBody("body1", nonzeroMass, false);
mbgraph.addBody("body2", nonzeroMass, false);
mbgraph.addBody("body3", nonzeroMass, false);
mbgraph.addBody("body4", nonzeroMass, false);
mbgraph.addBody("body5", nonzeroMass, false);
mbgraph.addJoint("pin1", "pin", "ground", "body1", false);
mbgraph.addJoint("pin2", "pin", "body1", "body2", false);
mbgraph.addJoint("pin3", "pin", "body2", "body3", false);
mbgraph.addJoint("pin4", "pin", "body3", "body4", false);
mbgraph.addJoint("pin5", "pin", "body4", "body5", false);
mbgraph.generateGraph();
// First, some basic tests.
SimTK_TEST(mbgraph.getNumJointTypes() == 3); // include weld and free.
SimTK_TEST(mbgraph.getJointTypeNum("weld") == 0);
SimTK_TEST(mbgraph.getJointTypeNum("free") == 1);
SimTK_TEST(mbgraph.getJointTypeNum("pin") == 2); // 3rd joint.
SimTK_TEST(mbgraph.getGroundBodyName() == "ground");
SimTK_TEST(mbgraph.getNumBodies() == 6);
SimTK_TEST(mbgraph.getBodyNum("body3") == 3); // ground is 0th body.
SimTK_TEST(mbgraph.getNumJoints() == 5);
SimTK_TEST(mbgraph.getJointNum("pin4") == 3);
SimTK_TEST(mbgraph.getNumLoopConstraints() == 0);
SimTK_TEST(mbgraph.getNumMobilizers() == 5);
for (int i = 0; i < mbgraph.getNumMobilizers(); ++i) {
const auto& mobilizer = mbgraph.getMobilizer(i);
SimTK_TEST(!mobilizer.isAddedBaseMobilizer());
SimTK_TEST(!mobilizer.isSlaveMobilizer());
SimTK_TEST(!mobilizer.isReversedFromJoint());
SimTK_TEST(mobilizer.getJointTypeName() == "pin");
SimTK_TEST(mobilizer.getNumFragments() == 1);
SimTK_TEST(mobilizer.getLevel() == i + 1);
}
}
// This test ensures that the graph maker produces the same topology for a
// 5-body chain of pin joints (ground-body1-body2-body3-body4-body5) whether or
// not body2 is massless.
// This test was suggested by Sherm here:
// https://github.com/simbody/simbody/pull/592
void testIntermediateMasslessBody() {
MultibodyGraphMaker mbgraph;
mbgraph.addJointType("pin", 1);
double nonzeroMass = 1.8;
mbgraph.addBody("ground", 0, false);
mbgraph.addBody("body1", nonzeroMass, false);
mbgraph.addBody("body2", 0, false); // <-- Massless.
mbgraph.addBody("body3", nonzeroMass, false);
mbgraph.addBody("body4", nonzeroMass, false);
mbgraph.addBody("body5", nonzeroMass, false);
mbgraph.addJoint("pin1", "pin", "ground", "body1", false);
mbgraph.addJoint("pin2", "pin", "body1", "body2", false);
mbgraph.addJoint("pin3", "pin", "body2", "body3", false);
mbgraph.addJoint("pin4", "pin", "body3", "body4", false);
mbgraph.addJoint("pin5", "pin", "body4", "body5", false);
mbgraph.generateGraph();
SimTK_TEST(mbgraph.getNumMobilizers() == 5);
for (int i = 0; i < mbgraph.getNumMobilizers(); ++i) {
const auto& mobilizer = mbgraph.getMobilizer(i);
SimTK_TEST(!mobilizer.isAddedBaseMobilizer());
SimTK_TEST(!mobilizer.isSlaveMobilizer());
SimTK_TEST(!mobilizer.isReversedFromJoint());
SimTK_TEST(mobilizer.getJointTypeName() == "pin");
SimTK_TEST(mobilizer.getNumFragments() == 1);
// Here's the test that the resulting graph is as expected:
SimTK_TEST(mobilizer.getLevel() == i + 1);
}
}
// Terminal massless bodies are not allowed (unless welded to a massful body).
void testTerminalMasslessBody() {
MultibodyGraphMaker mbgraph;
mbgraph.addJointType("pin", 1);
mbgraph.addBody("ground", 0, false);
mbgraph.addBody("body1", 0, false); // massless
mbgraph.addJoint("pin1", "pin", "ground", "body1", false);
SimTK_TEST_MUST_THROW_EXC(mbgraph.generateGraph(), std::runtime_error);
// If the terminal massless body is welded, then there's no issue.
mbgraph.deleteJoint("pin1");
mbgraph.addJoint("pin1", "weld", "ground", "body1", false);
mbgraph.generateGraph();
}
// This is a basic test for how MultibodyGraphMaker handles a system with a
// loop (four-bar linkage). There are many other settings surrounding loops
// that could be tested.
void testLoop() {
MultibodyGraphMaker mbgraph;
double nonzeroMass = 1.8;
mbgraph.addJointType("pin", 1);
mbgraph.addBody("ground", 0, false);
mbgraph.addBody("body1", nonzeroMass, false);
mbgraph.addBody("body2", nonzeroMass, false);
mbgraph.addBody("body3", nonzeroMass, false);
mbgraph.addJoint("pin1", "pin", "ground", "body1", false);
mbgraph.addJoint("pin2", "pin", "body1", "body2", false);
mbgraph.addJoint("pin3", "pin", "body2", "body3", false);
mbgraph.addJoint("pin4", "pin", "body3", "ground", false);
mbgraph.generateGraph();
mbgraph.dumpGraph(std::cout);
SimTK_TEST(mbgraph.getNumJointTypes() == 3); // include weld and free.
SimTK_TEST(mbgraph.getJointTypeNum("weld") == 0);
SimTK_TEST(mbgraph.getJointTypeNum("free") == 1);
SimTK_TEST(mbgraph.getJointTypeNum("pin") == 2); // 3rd joint.
SimTK_TEST(mbgraph.getGroundBodyName() == "ground");
SimTK_TEST(mbgraph.getNumBodies() == 5); // body3 is split into two bodies.
SimTK_TEST(mbgraph.getBody(4).name == "#body3_slave_1");
SimTK_TEST(mbgraph.getNumJoints() == 4);
// Still no loop constraints; the loop is broken by splitting a body and
// adding a weld constraint.
SimTK_TEST(mbgraph.getNumLoopConstraints() == 0);
SimTK_TEST(mbgraph.getNumMobilizers() == 4);
// Resulting mobilizers (breadth-first):
// 0: pin1 ground->body1
// 1: pin4 ground->body3 (reversed)
// 2: pin2 body1->body2
// 3: pin3 body2->#body3_slave_1
SimTK_TEST(mbgraph.getMobilizer(0).getLevel() == 1);
SimTK_TEST(mbgraph.getMobilizer(1).getLevel() == 1);
SimTK_TEST(mbgraph.getMobilizer(2).getLevel() == 2);
SimTK_TEST(mbgraph.getMobilizer(3).getLevel() == 3);
for (int i = 0; i < mbgraph.getNumMobilizers(); ++i) {
const auto& mobilizer = mbgraph.getMobilizer(i);
SimTK_TEST(!mobilizer.isAddedBaseMobilizer());
// The 4th mobilizer is a slave mobilizer (child body is a slave).
SimTK_TEST(mobilizer.isSlaveMobilizer() == (i == 3));
SimTK_TEST(mobilizer.isReversedFromJoint() == (i == 1));
SimTK_TEST(mobilizer.getJointTypeName() == "pin");
// Body 3 is split, and it's the outboard body for mobilizers 1 and 3.
SimTK_TEST(mobilizer.getNumFragments() == (i == 1 || i == 3 ? 2 : 1));
}
}
int main() {
SimTK_START_TEST("TestMultibodyGraphMaker");
SimTK_SUBTEST(testSerialChain);
SimTK_SUBTEST(testIntermediateMasslessBody);
SimTK_SUBTEST(testTerminalMasslessBody);
SimTK_SUBTEST(testLoop);
SimTK_END_TEST();
}
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