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SnippetFixedTendon.cpp
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SnippetFixedTendon.cpp
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// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
// * Neither the name of NVIDIA CORPORATION nor the names of its
// contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ''AS IS'' AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
// OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// Copyright (c) 2008-2024 NVIDIA Corporation. All rights reserved.
// Copyright (c) 2004-2008 AGEIA Technologies, Inc. All rights reserved.
// Copyright (c) 2001-2004 NovodeX AG. All rights reserved.
// ***************************************************************************************
// This snippet demonstrates the use of a fixed tendon to mirror articulation joint angles
// ***************************************************************************************
#include <ctype.h>
#include "PxPhysicsAPI.h"
#include "../snippetutils/SnippetUtils.h"
#include "../snippetcommon/SnippetPrint.h"
#include "../snippetcommon/SnippetPVD.h"
using namespace physx;
static PxDefaultAllocator gAllocator;
static PxDefaultErrorCallback gErrorCallback;
static PxFoundation* gFoundation = NULL;
static PxPhysics* gPhysics = NULL;
static PxDefaultCpuDispatcher* gDispatcher = NULL;
static PxScene* gScene = NULL;
static PxMaterial* gMaterial = NULL;
static PxPvd* gPvd = NULL;
static PxArticulationReducedCoordinate* gArticulation = NULL;
static PxArticulationJointReducedCoordinate* gDriveJoint = NULL;
static const PxReal gGravity = 9.81f;
static PxReal gDriveTargetPos = 0.0f;
static void createArticulation()
{
gArticulation->setArticulationFlags(PxArticulationFlag::eFIX_BASE);
gArticulation->setSolverIterationCounts(10, 1);
// link geometry and density:
const PxVec3 halfLengths(0.50f, 0.05f, 0.05f);
const PxBoxGeometry linkGeom = PxBoxGeometry(halfLengths);
const PxReal density = 1000.0f;
//Create links
PxTransform pose = PxTransform(PxIdentity);
pose.p.y = 3.0f;
pose.p.x -= 2.0f * halfLengths.x;
PxArticulationLink* parent = NULL;
const PxU32 numLinks = 3;
for(PxU32 j = 0; j < numLinks; ++j)
{
pose.p.x += 2.0f * halfLengths.x;
parent = gArticulation->createLink(parent, pose);
PxRigidActorExt::createExclusiveShape(*parent, linkGeom, *gMaterial);
PxRigidBodyExt::updateMassAndInertia(*parent, density);
PxArticulationJointReducedCoordinate* joint = parent->getInboundJoint();
if(joint)
{
PxVec3 parentOffset(halfLengths.x, 0.0f, 0.0f);
PxVec3 childOffset(-halfLengths.x, 0.0f, 0.0f);
joint->setParentPose(PxTransform(parentOffset, PxQuat(PxIdentity)));
joint->setChildPose(PxTransform(childOffset, PxQuat(PxIdentity)));
joint->setJointType(PxArticulationJointType::eREVOLUTE);
joint->setMotion(PxArticulationAxis::eSWING2, PxArticulationMotion::eFREE);
}
}
// tendon and drive stiffness sizing
// assuming all links extend horizontally, size to allow for two degrees
// deviation due to gravity
const PxReal linkMass = parent->getMass();
const PxReal deflectionAngle = 2.0f * PxPi / 180.0f; // two degrees
// moment arm of first link is one half-length, for second it is three half-lengths
const PxReal gravityTorque = gGravity * linkMass * (halfLengths.x + 3.0f * halfLengths.x);
const PxReal driveStiffness = gravityTorque / deflectionAngle;
const PxReal driveDamping = 0.2f * driveStiffness;
// same idea for the tendon, but it has to support only a single link
const PxReal tendonStiffness = gGravity * linkMass * halfLengths.x / deflectionAngle;
const PxReal tendonDamping = 0.2f * tendonStiffness;
// compute drive target angle that compensates, statically, for the first fixed tendon joint
// torque acting on the drive joint:
const PxReal targetAngle = PxPiDivFour;
const PxReal tendonTorque = targetAngle * tendonStiffness;
gDriveTargetPos = targetAngle + tendonTorque / driveStiffness;
// setup fixed tendon
PxArticulationLink* links[numLinks];
gArticulation->getLinks(links, numLinks, 0u);
PxArticulationFixedTendon* tendon = gArticulation->createFixedTendon();
tendon->setLimitStiffness(0.0f);
tendon->setDamping(tendonDamping);
tendon->setStiffness(tendonStiffness);
tendon->setRestLength(0.f);
tendon->setOffset(0.f);
PxArticulationTendonJoint* tendonParentJoint = NULL;
// root fixed-tendon joint - does not contribute to length so its coefficient and axis are irrelevant
// but its parent link experiences all tendon-joint reaction forces
tendonParentJoint = tendon->createTendonJoint(tendonParentJoint, PxArticulationAxis::eSWING2, 42.0f, 1.f/42.f, links[0]);
// drive joint
tendonParentJoint = tendon->createTendonJoint(tendonParentJoint, PxArticulationAxis::eSWING2, 1.0f, 1.f, links[1]);
// second joint that is driven only by the tendon - negative coefficient to mirror angle of drive joint
tendonParentJoint = tendon->createTendonJoint(tendonParentJoint, PxArticulationAxis::eSWING2, -1.0f, -1.0f, links[2]);
// configure joint drive
gDriveJoint = links[1]->getInboundJoint();
PxArticulationDrive driveConfiguration;
driveConfiguration.damping = driveDamping;
driveConfiguration.stiffness = driveStiffness;
driveConfiguration.maxForce = PX_MAX_F32;
driveConfiguration.driveType = PxArticulationDriveType::eFORCE;
gDriveJoint->setDriveParams(PxArticulationAxis::eSWING2, driveConfiguration);
gDriveJoint->setDriveVelocity(PxArticulationAxis::eSWING2, 0.0f);
gDriveJoint->setDriveTarget(PxArticulationAxis::eSWING2, 0.0f);
// add articulation to scene:
gScene->addArticulation(*gArticulation);
}
void initPhysics(bool /*interactive*/)
{
gFoundation = PxCreateFoundation(PX_PHYSICS_VERSION, gAllocator, gErrorCallback);
gPvd = PxCreatePvd(*gFoundation);
PxPvdTransport* transport = PxDefaultPvdSocketTransportCreate(PVD_HOST, 5425, 10);
gPvd->connect(*transport,PxPvdInstrumentationFlag::eALL);
gPhysics = PxCreatePhysics(PX_PHYSICS_VERSION, *gFoundation, PxTolerancesScale(), true, gPvd);
PxInitExtensions(*gPhysics, gPvd);
PxSceneDesc sceneDesc(gPhysics->getTolerancesScale());
sceneDesc.gravity = PxVec3(0.0f, -gGravity, 0.0f);
PxU32 numCores = SnippetUtils::getNbPhysicalCores();
gDispatcher = PxDefaultCpuDispatcherCreate(numCores == 0 ? 0 : numCores - 1);
sceneDesc.cpuDispatcher = gDispatcher;
sceneDesc.filterShader = PxDefaultSimulationFilterShader;
sceneDesc.solverType = PxSolverType::eTGS;
sceneDesc.filterShader = PxDefaultSimulationFilterShader;
gScene = gPhysics->createScene(sceneDesc);
gMaterial = gPhysics->createMaterial(0.5f, 0.5f, 0.f);
gArticulation = gPhysics->createArticulationReducedCoordinate();
createArticulation();
}
void stepPhysics(bool /*interactive*/)
{
static bool dir = false;
static PxReal time = 0.0f;
const PxReal switchTime = 3.0f;
const PxReal dt = 1.0f / 60.f;
time += dt;
if(time > switchTime)
{
if(dir)
{
gDriveJoint->setDriveTarget(PxArticulationAxis::eSWING2, 0.0f);
}
else
{
gDriveJoint->setDriveTarget(PxArticulationAxis::eSWING2, gDriveTargetPos);
}
dir = !dir;
time = 0.0f;
}
gScene->simulate(dt);
gScene->fetchResults(true);
}
void cleanupPhysics(bool /*interactive*/)
{
PX_RELEASE(gArticulation);
PX_RELEASE(gScene);
PX_RELEASE(gDispatcher);
PX_RELEASE(gPhysics);
PxPvdTransport* transport = gPvd->getTransport();
PX_RELEASE(gPvd);
PX_RELEASE(transport);
PxCloseExtensions();
PX_RELEASE(gFoundation);
printf("SnippetFixedTendon done.\n");
}
int snippetMain(int, const char*const*)
{
#ifdef RENDER_SNIPPET
extern void renderLoop();
renderLoop();
#else
static const PxU32 frameCount = 100;
initPhysics(false);
for(PxU32 i=0; i<frameCount; i++)
stepPhysics(false);
cleanupPhysics(false);
#endif
return 0;
}