Create InclinedPlane,Newton's Cradle and Multi-Pendulum examples for the Bullet Example Browser.
This commit is contained in:
Benjamin Ellenberger
350
examples/ExtendedTutorials/NewtonsCradle.cpp
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350
examples/ExtendedTutorials/NewtonsCradle.cpp
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/*
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Bullet Continuous Collision Detection and Physics Library
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Copyright (c) 2015 Google Inc. http://bulletphysics.org
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This software is provided 'as-is', without any express or implied warranty.
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In no event will the authors be held liable for any damages arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it freely,
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subject to the following restrictions:
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1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
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3. This notice may not be removed or altered from any source distribution.
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*/
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#include "NewtonsCradle.h"
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#include <vector> // TODO: Should I use another data structure?
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#include <iterator>
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#include "btBulletDynamicsCommon.h"
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#include "LinearMath/btVector3.h"
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#include "LinearMath/btAlignedObjectArray.h"
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#include "../CommonInterfaces/CommonRigidBodyBase.h"
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#include "../CommonInterfaces/CommonParameterInterface.h"
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static btScalar gPendulaQty = 5; // Number of pendula in newton's cradle
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//TODO: This would actually be an Integer, but the Slider does not like integers, so I floor it when changed
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static btScalar gDisplacedPendula = 1; // number of displaced pendula
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//TODO: This is an int as well
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static btScalar gPendulaRestitution = 1; // pendula restition when hitting against each other
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static btScalar gSphereRadius = 1; // pendula radius
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static btScalar gCurrentPendulumLength = 8; // current pendula length
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static btScalar gInitialPendulumLength = 8; // default pendula length
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static btScalar gForcingForce = 30; // default force to displace the pendula
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struct NewtonsCradleExample: public CommonRigidBodyBase {
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NewtonsCradleExample(struct GUIHelperInterface* helper) :
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CommonRigidBodyBase(helper) {
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}
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virtual ~NewtonsCradleExample() {
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}
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virtual void initPhysics();
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virtual void renderScene();
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virtual void createPendulum(btSphereShape* colShape, btScalar xPosition,
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btScalar yPosition, btScalar zPosition, btScalar length, btScalar mass);
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virtual void changePendulaLength(btScalar length);
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virtual void changePendulaRestitution(btScalar restitution);
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virtual void stepSimulation(float deltaTime);
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virtual bool keyboardCallback(int key, int state);
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void resetCamera() {
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float dist = 41;
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float pitch = 52;
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float yaw = 35;
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float targetPos[3] = { 0, 0.46, 0 };
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m_guiHelper->resetCamera(dist, pitch, yaw, targetPos[0], targetPos[1],
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targetPos[2]);
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}
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std::vector<btSliderConstraint*> constraints;
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std::vector<btRigidBody*> pendula;
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};
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static NewtonsCradleExample* nex = NULL;
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void onPendulaLengthChanged(float pendulaLength);
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void onPendulaRestitutionChanged(float pendulaRestitution);
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void floorSliderValue(float notUsed);
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void NewtonsCradleExample::initPhysics() {
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{ // create a slider to change the number of pendula
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SliderParams slider("Number of Pendula", &gPendulaQty);
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slider.m_minVal = 1;
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slider.m_maxVal = 50;
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slider.m_callback = floorSliderValue; // hack to get integer values
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slider.m_clampToNotches = false;
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m_guiHelper->getParameterInterface()->registerSliderFloatParameter(
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slider);
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}
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{ // create a slider to change the number of displaced pendula
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SliderParams slider("Number of Displaced Pendula", &gDisplacedPendula);
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slider.m_minVal = 0;
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slider.m_maxVal = 49;
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slider.m_callback = floorSliderValue; // hack to get integer values
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slider.m_clampToNotches = false;
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m_guiHelper->getParameterInterface()->registerSliderFloatParameter(
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slider);
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}
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{ // create a slider to change the pendula restitution
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SliderParams slider("Pendula Restitution", &gPendulaRestitution);
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slider.m_minVal = 0;
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slider.m_maxVal = 1;
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slider.m_clampToNotches = false;
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slider.m_callback = onPendulaRestitutionChanged;
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m_guiHelper->getParameterInterface()->registerSliderFloatParameter(
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slider);
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}
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{ // create a slider to change the pendulum length
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SliderParams slider("Pendula Length", &gCurrentPendulumLength);
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slider.m_minVal = 0;
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slider.m_maxVal = 49;
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slider.m_clampToNotches = false;
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slider.m_callback = onPendulaLengthChanged;
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m_guiHelper->getParameterInterface()->registerSliderFloatParameter(
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slider);
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}
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{ // create a slider to change the force to displace the lowest pendulum
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SliderParams slider("Displacement force", &gForcingForce);
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slider.m_minVal = 0.1;
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slider.m_maxVal = 200;
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slider.m_clampToNotches = false;
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m_guiHelper->getParameterInterface()->registerSliderFloatParameter(
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slider);
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}
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m_guiHelper->setUpAxis(1);
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createEmptyDynamicsWorld();
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// create a debug drawer
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m_guiHelper->createPhysicsDebugDrawer(m_dynamicsWorld);
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if (m_dynamicsWorld->getDebugDrawer())
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m_dynamicsWorld->getDebugDrawer()->setDebugMode(
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btIDebugDraw::DBG_DrawWireframe
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+ btIDebugDraw::DBG_DrawContactPoints
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+ btIDebugDraw::DBG_DrawConstraints
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+ btIDebugDraw::DBG_DrawConstraintLimits);
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{ // create the pendulum starting at the indicated position below and where each pendulum has the following mass
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btScalar pendulumMass(1.f);
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btScalar xPosition(0.0f); // initial left-most pendulum position
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btScalar yPosition(15.0f);
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btScalar zPosition(0.0f);
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// Re-using the same collision is better for memory usage and performance
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btSphereShape* pendulumShape = new btSphereShape(gSphereRadius);
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m_collisionShapes.push_back(pendulumShape);
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for (int i = 0; i < floor(gPendulaQty); i++) {
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// create pendulum
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createPendulum(pendulumShape, xPosition, yPosition,zPosition,
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gInitialPendulumLength, pendulumMass);
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// displace the pendula 1.05 sphere size, so that they all nearly touch (small spacings in between
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xPosition -= 2.1f * gSphereRadius;
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}
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}
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m_guiHelper->autogenerateGraphicsObjects(m_dynamicsWorld);
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}
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void NewtonsCradleExample::stepSimulation(float deltaTime) {
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if (m_dynamicsWorld) {
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m_dynamicsWorld->stepSimulation(deltaTime);
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}
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}
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void NewtonsCradleExample::createPendulum(btSphereShape* colShape,
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btScalar xPosition, btScalar yPosition, btScalar zPosition, btScalar length, btScalar mass) {
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// The pendulum looks like this (names when built):
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// O topSphere
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// |
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// O bottomSphere
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//create a dynamic pendulum
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btTransform startTransform;
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startTransform.setIdentity();
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// position the top sphere above ground with a moving x position
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startTransform.setOrigin(
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btVector3(btScalar(xPosition), btScalar(yPosition), btScalar(zPosition)));
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startTransform.setRotation(btQuaternion(0, 0, 0, 1)); // zero rotation
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btRigidBody* topSphere = createRigidBody(mass, startTransform, colShape);
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// position the bottom sphere below the top sphere
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startTransform.setOrigin(
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btVector3(btScalar(xPosition), btScalar(yPosition - length),
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btScalar(zPosition)));
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startTransform.setRotation(btQuaternion(0, 0, 0, 1)); // zero rotation
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btRigidBody* bottomSphere = createRigidBody(mass, startTransform, colShape);
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bottomSphere->setFriction(0); // we do not need friction here
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pendula.push_back(bottomSphere);
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// disable the deactivation when objects do not move anymore
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topSphere->setActivationState(DISABLE_DEACTIVATION);
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bottomSphere->setActivationState(DISABLE_DEACTIVATION);
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bottomSphere->setRestitution(gPendulaRestitution); // set pendula restitution
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//make the top sphere position "fixed" to the world by attaching with a point to point constraint
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// The pivot is defined in the reference frame of topSphere, so the attachment is exactly at the center of the topSphere
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btVector3 constraintPivot(btVector3(0.0f, 0.0f, 0.0f));
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btPoint2PointConstraint* p2pconst = new btPoint2PointConstraint(*topSphere,
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constraintPivot);
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p2pconst->setDbgDrawSize(btScalar(5.f)); // set the size of the debug drawing
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// add the constraint to the world
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m_dynamicsWorld->addConstraint(p2pconst, true);
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//create constraint between spheres
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// this is represented by the constraint pivot in the local frames of reference of both constrained spheres
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// furthermore we need to rotate the constraint appropriately to orient it correctly in space
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btTransform constraintPivotInTopSphereRF, constraintPivotInBottomSphereRF;
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constraintPivotInTopSphereRF.setIdentity();
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constraintPivotInBottomSphereRF.setIdentity();
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// the slider constraint is x aligned per default, but we want it to be y aligned, therefore we rotate it
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btQuaternion qt;
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qt.setEuler(0, 0, -SIMD_HALF_PI);
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constraintPivotInTopSphereRF.setRotation(qt); //we use Y like up Axis
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constraintPivotInBottomSphereRF.setRotation(qt); //we use Y like up Axis
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//Obtain the position of topSphere in local reference frame of bottomSphere (the pivot is therefore in the center of topSphere)
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btVector3 topSphereInBottomSphereRF =
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(bottomSphere->getWorldTransform().inverse()(
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topSphere->getWorldTransform().getOrigin()));
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constraintPivotInBottomSphereRF.setOrigin(topSphereInBottomSphereRF);
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btSliderConstraint* sliderConst = new btSliderConstraint(*topSphere,
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*bottomSphere, constraintPivotInTopSphereRF, constraintPivotInBottomSphereRF, true);
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sliderConst->setDbgDrawSize(btScalar(5.f)); // set the size of the debug drawing
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// set limits
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// the initial setup of the constraint defines the origins of the limit dimensions,
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// therefore we set both limits directly to the current position of the topSphere
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sliderConst->setLowerLinLimit(btScalar(0));
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sliderConst->setUpperLinLimit(btScalar(0));
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sliderConst->setLowerAngLimit(btScalar(0));
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sliderConst->setUpperAngLimit(btScalar(0));
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constraints.push_back(sliderConst);
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// add the constraint to the world
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m_dynamicsWorld->addConstraint(sliderConst, true);
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}
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void NewtonsCradleExample::changePendulaLength(btScalar length) {
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btScalar lowerLimit = -gInitialPendulumLength;
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for (std::vector<btSliderConstraint*>::iterator sit = constraints.begin();
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sit != constraints.end(); sit++) {
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btAssert((*sit) && "Null constraint");
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//if the pendulum is being shortened beyond it's own length, we don't let the lower sphere to go past the upper one
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if (lowerLimit <= length) {
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(*sit)->setLowerLinLimit(length + lowerLimit);
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(*sit)->setUpperLinLimit(length + lowerLimit);
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}
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}
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}
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void NewtonsCradleExample::changePendulaRestitution(btScalar restitution) {
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for (std::vector<btRigidBody*>::iterator rit = pendula.begin();
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rit != pendula.end(); rit++) {
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btAssert((*rit) && "Null constraint");
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(*rit)->setRestitution(restitution);
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}
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}
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void NewtonsCradleExample::renderScene() {
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CommonRigidBodyBase::renderScene();
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}
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bool NewtonsCradleExample::keyboardCallback(int key, int state) {
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//b3Printf("Key pressed: %d in state %d \n",key,state);
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//key 1, key 2, key 3
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switch (key) {
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case 49 /*ASCII for 1*/: {
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//assumption: Sphere are aligned in Z axis
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btScalar newLimit = gCurrentPendulumLength + 0.1;
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changePendulaLength(newLimit);
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gCurrentPendulumLength = newLimit;
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b3Printf("Increase pendulum length to %f", gCurrentPendulumLength);
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return true;
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}
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case 50 /*ASCII for 2*/: {
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//assumption: Sphere are aligned in Z axis
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btScalar newLimit = gCurrentPendulumLength - 0.1;
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//is being shortened beyond it's own length, we don't let the lower sphere to go over the upper one
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if (0 <= newLimit) {
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changePendulaLength(newLimit);
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gCurrentPendulumLength = newLimit;
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}
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b3Printf("Decrease pendulum length to %f", gCurrentPendulumLength);
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return true;
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}
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case 51 /*ASCII for 3*/: {
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for (int i = 0; i < gDisplacedPendula; i++) {
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if (gDisplacedPendula >= 0 && gDisplacedPendula <= gPendulaQty)
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pendula[i]->applyCentralForce(btVector3(gForcingForce, 0, 0));
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}
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return true;
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}
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}
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return false;
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}
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// GUI parameter modifiers
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void onPendulaLengthChanged(float pendulaLength) {
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if (nex){
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nex->changePendulaLength(pendulaLength);
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//b3Printf("Pendula length changed to %f \n",sliderValue );
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}
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}
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void onPendulaRestitutionChanged(float pendulaRestitution) {
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if (nex){
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nex->changePendulaRestitution(pendulaRestitution);
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}
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}
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void floorSliderValue(float notUsed) {
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gPendulaQty = floor(gPendulaQty);
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gDisplacedPendula = floor(gDisplacedPendula);
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}
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CommonExampleInterface* ET_NewtonsCradleCreateFunc(
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CommonExampleOptions& options) {
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nex = new NewtonsCradleExample(options.m_guiHelper);
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return nex;
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}
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