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From James Moliere,

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"   The code below is to show how a heirarchy of objects can be made within a scenegraph.
    In other words, how there can be a parent/child relationship between objects such
    that when a parent is rotated or translated, the children move is respect to it's
    parent movement.  A robotic arm is used in this example because this is what I'm
    using OSG for."
This commit is contained in:
Robert Osfield
2008-10-14 15:24:39 +00:00
parent e4057b65ee
commit 8c6f65caca
3 changed files with 501 additions and 0 deletions
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1
examples/CMakeLists.txt
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@@ -28,6 +28,7 @@ IF(DYNAMIC_OPENSCENEGRAPH)
ADD_SUBDIRECTORY(osgcompositeviewer)
ADD_SUBDIRECTORY(osgcopy)
ADD_SUBDIRECTORY(osgcubemap)
ADD_SUBDIRECTORY(osgrobot)
ADD_SUBDIRECTORY(osgdelaunay)
ADD_SUBDIRECTORY(osgdepthpartition)
ADD_SUBDIRECTORY(osgdepthpeeling)

4
examples/osgrobot/CMakeLists.txt Normal file
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@@ -0,0 +1,4 @@
SET(TARGET_SRC osgrobot.cpp )
#### end var setup ###
SETUP_EXAMPLE(osgrobot)

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examples/osgrobot/osgrobot.cpp Normal file
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/* OpenSceneGraph example, osgrobot.cpp.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
/*
The code below is to show how a heirarchy of objects can be made within a scenegraph.
In other words, how there can be a parent/child relationship between objects such
that when a parent is rotated or translated, the children move is respect to it's
parent movement. A robotic arm is used in this example because this is what I'm
using OSG for.
To rotate the joints use the following table to rotate each respective joint.
joint key rotation
1 q + 1 degree
1 a - 1 degree
2 w + 1 degree
2 s - 1 degree
3 e + 1 degree
3 d - 1 degree
4 r + 1 degree
4 f - 1 degree
5 t + 1 degree
5 g - 1 degree
6 y + 1 degree
6 h - 1 degree
In many robotics projects, the x and z axis are only used to define the positions
of the joints of a robotic arm. By not using the y-axis, the mathematics of
inverse kinematics becomes easier (and in some cases possible). All joint rotations
are rotated about the z-axis. If you toggle the variable 'showAxis' to true, an
x (color red), y (color green), and z (color blue) axis will display. Using the
thumb of the right hand to point in the same direction of the z-axis, use the right
hand rule to define a positive angle of rotation.
The robotic arm in general follows the algorithm
rotate about the x axis, translate along the x-axis, translate along the z axis,
and then rotate about the z-axis. There is 1 exception in the method buildJoint3(...)
where it was necessary to add a 'cheat' to get the joints to align properly. In a
real robotics project such as this, the tube (see buildTube2(...) method) would not
be a part of the mathematics and thus, not have to be drawn and would not require
the cheat. To learn moue about positioning joints using only the x and z axis,
web search 'Denavit-Hartenberg'. wikipedia has comments at the URL...
http://en.wikipedia.org/wiki/Robotics_conventions#Denavit-Hartenberg_link_frame_convention_.28DH.29
Lessons learned with osg...
When starting this work I was very new to OSG. When I first placed a cylinder
in a scene and rotated the cylinder about the z and x axis, I noticed that the rotation
is about the barycenter of the object for both axis. I wanted a rotation about the z-axis
to be along the length of the tube (which OSG gives for free -- not always true with
all scenegraphs) while the rotation about the x and y axis about the
beginning (or start position) of the tube. Knowing what I know about barycenters
I positioned the shape along the -height/2 (see example 1 below)
-- believing the offset -height/2 would place the axis of rotation at the start of
the tube. I was certainly wrong about this and found out the equation needs to
be height/2.
...
example 1
joint->addDrawable(new osg::ShapeDrawable(new osg::Capsule(osg::Vec3(0.0f,0.0f,height/2),radius,height),hints));
...
author: James Moliere
date written: 10/12/2008
*/
#include <osg/Geode>
#include <osg/ShapeDrawable>
#include <osg/Material>
#include <osg/Texture2D>
#include <osgViewer/Viewer>
#include <iostream>
#include <osgDB/ReadFile>
#include <osg/Math>
#include <osg/Matrixd>
#include <osg/MatrixTransform>
#include <osg/Vec3d>
#include <iostream>
#include <osg/PositionAttitudeTransform>
float jointAngle1;
float jointAngle2;
float jointAngle3;
float jointAngle4;
float jointAngle5;
float jointAngle6;
float EndEffector;
void createAxis(osg::Transform* previousJoint);
osg::MatrixTransform* joint1;
osg::MatrixTransform* joint2;
osg::MatrixTransform* joint3;
osg::MatrixTransform* joint4;
osg::MatrixTransform* joint5;
osg::MatrixTransform* joint6;
osg::MatrixTransform* buildJoint1(osg::MatrixTransform* previousJoint);
osg::MatrixTransform* buildJoint2(osg::MatrixTransform* previousJoint);
osg::MatrixTransform* buildTube2(osg::MatrixTransform* previousJoint);
osg::MatrixTransform* buildJoint3(osg::MatrixTransform* previousJoint);
osg::MatrixTransform* buildJoint4(osg::MatrixTransform* previousJoint);
osg::MatrixTransform* buildTube5(osg::MatrixTransform* previousJoint);
osg::MatrixTransform* buildJoint5(osg::MatrixTransform* previousJoint);
osg::MatrixTransform* buildJoint6(osg::MatrixTransform* previousJoint);
osg::MatrixTransform* buildEndEffector();
osg::TessellationHints* hints = new osg::TessellationHints;
bool showAxis;
class KeyboardEventHandler : public osgGA::GUIEventHandler
{
public:
KeyboardEventHandler()
{}
static void rotate(float angle,osg::MatrixTransform *joint)
{
osg::Matrix zRot;
zRot.makeRotate(angle, 0.0,0.0,1.0);
joint->setMatrix(zRot*joint->getMatrix());
}
virtual bool handle(const osgGA::GUIEventAdapter& ea,osgGA::GUIActionAdapter&)
{
switch (ea.getEventType())
{
case(osgGA::GUIEventAdapter::KEYDOWN):
{
switch (ea.getKey())
{
case 'q':
rotate(M_PIl/180, joint1);
return true;
case 'a':
rotate(-M_PIl/180, joint1);
return true;
case 'w':
rotate(M_PIl/180, joint2);
return true;
case 's':
rotate(-M_PIl/180, joint2);
return true;
case 'e':
rotate(M_PIl/180, joint3);
return true;
case 'd':
rotate(-M_PIl/180, joint3);
return true;
case 'r':
rotate(M_PIl/180, joint4);
return true;
case 'f':
rotate(-M_PIl/180, joint4);
return true;
case 't':
rotate(M_PIl/180, joint5);
return true;
case 'g':
rotate(-M_PIl/180, joint5);
return true;
case 'y':
rotate(M_PIl/180, joint6);
return true;
case 'h':
rotate(-M_PIl/180, joint6);
return true;
}
}
default:
break;
}
//return false to allow mouse manipulation
return false;
}
};
osg::Group* createShapes()
{
osg::Group* group = new osg::Group();
osg::MatrixTransform* transform =new osg::MatrixTransform();
group->addChild(transform);
joint1 = buildJoint1(transform);
joint2 = buildJoint2(joint1);
osg::MatrixTransform* tube2= buildTube2(joint2);
joint3 = buildJoint3(tube2);
joint4 = buildJoint4(joint3);
osg::MatrixTransform *tube5 = buildTube5(joint4);
joint5 = buildJoint5(tube5);
joint6= buildJoint6(joint5);
joint6->addChild( buildEndEffector());
return group;
}
osg::MatrixTransform* buildJoint1(osg::MatrixTransform* previousJoint)
{
osg::MatrixTransform* xTransform =new osg::MatrixTransform();
previousJoint->addChild(xTransform);
float radius = 6.7640f;
float height = 45.0f;
osg::Geode* joint = new osg::Geode();
xTransform->addChild(joint);
//The cylinder's barycenter is the point of rotation.
//For this project, the x and y axis of rotation needs to be at the start of the cylinder and the
//axis of rotation about the z axis needs to be at the center of the cylinder.
// this is where height/2 is used -- to offset x and y axis barycenter.
// note: we did not use -height/2
joint->addDrawable(new osg::ShapeDrawable(new osg::Cylinder(osg::Vec3(0.0f,0.0f,height/2),radius,height),hints));
osg::MatrixTransform *zTransform = new osg::MatrixTransform();
xTransform->addChild(zTransform);
osg::Matrix zTrans=osg::Matrix::translate(0.0, 0.0, height);
osg::Matrix zRot= osg::Matrix::rotate(jointAngle1, 0.0, 0.0, 1.0);
zTransform->setMatrix(zTrans*zRot);
return zTransform;
}
osg::MatrixTransform* buildJoint2(osg::MatrixTransform* previousJoint)
{
if (showAxis)
{
createAxis(previousJoint);
}
double height = 17.6;
double radius = 4.45633;
osg::MatrixTransform* xTransform = new osg::MatrixTransform();
previousJoint->addChild(xTransform);
osg::Matrix xRot = osg::Matrix::rotate(M_PI_2, 1.0, 0.0, 0.0);
xTransform->setMatrix(xRot);
osg::Geode* joint = new osg::Geode();
joint->addDrawable(new osg::ShapeDrawable(new osg::Capsule(osg::Vec3(0.0f,0.0f,height/2),radius,height),hints));
xTransform->addChild(joint);
osg::MatrixTransform* zTransform = new osg::MatrixTransform();
osg::Matrix zTrans = osg::Matrix::translate( 0.0, 0.0, height);
osg::Matrix zRot = osg::Matrix::rotate(M_PI_2+jointAngle2, 0.0,0.0,1.0);
zTransform->setMatrix(zTrans*zRot);
xTransform->addChild(zTransform);
return zTransform;
}
osg::MatrixTransform* buildTube2(osg::MatrixTransform* previousJoint)
{
if (showAxis)
{
createAxis(previousJoint);
}
double height = 17.6;
double radius = 4.45633;
osg::MatrixTransform* xTransform = new osg::MatrixTransform();
previousJoint->addChild(xTransform);
osg::Matrix xRot = osg::Matrix::rotate(M_PI_2, 1.0,0.0,0.0);
xTransform->setMatrix(xRot);
osg::Geode* tube3 = new osg::Geode();
xTransform->addChild(tube3);
tube3->addDrawable(new osg::ShapeDrawable(new osg::Capsule(osg::Vec3(0.0f,0.0f,height/2),radius,height),hints));
osg::MatrixTransform* zTransform = new osg::MatrixTransform();
xTransform->addChild(zTransform);
osg::Matrix zTrans = osg::Matrix::translate(0,0,height);
zTransform->setMatrix(zTrans);
return zTransform;
}
osg::MatrixTransform* buildJoint3(osg::MatrixTransform* previousJoint)
{
double height =7.5;
double radius = 4.45633;
osg::Geode* joint = new osg::Geode();
osg::MatrixTransform* xTransform = new osg::MatrixTransform();
previousJoint->addChild(xTransform);
osg::Matrix xRot = osg::Matrix::rotate(-M_PI_2, 1.0, 0.0, 0.0);
xTransform->setMatrix(xRot);
if (showAxis)
{
createAxis(xTransform);
}
osg::MatrixTransform* zCheat = new osg::MatrixTransform();
osg::Matrix zTransCheat = osg::Matrix::translate(0.0,0.0,-height);
zCheat->setMatrix(zTransCheat);
xTransform->addChild(zCheat);
osg::ShapeDrawable *shape = new osg::ShapeDrawable(new osg::Capsule(osg::Vec3(0.0f,0.0f,height/2),radius,height),hints);
joint->addDrawable(shape);
zCheat->addChild(joint);
osg::MatrixTransform* zTransform = new osg::MatrixTransform();
zCheat->addChild(zTransform);
osg::Matrix zRot = osg::Matrix::rotate((float)jointAngle3, 0.0f, 0.0f, 1.0f);
osg::Matrix zTrans = osg::Matrix::translate(0,0,0);
zTransform->setMatrix(zTrans*zRot);
return zTransform;
}
osg::MatrixTransform* buildJoint4(osg::MatrixTransform* previousJoint)
{
double height = 17.5;
double radius = 2.86479;
osg::Geode* tube4 = new osg::Geode();
tube4->addDrawable(new osg::ShapeDrawable(new osg::Capsule(osg::Vec3(0.0f,0.0f,height/2),radius,height),hints));
osg::MatrixTransform* xTransform = new osg::MatrixTransform();
if (showAxis)
{
createAxis(xTransform);
}
previousJoint->addChild(xTransform);
xTransform->addChild(tube4);
osg::Matrix xRot= osg::Matrix::rotate(M_PI_2, 1,0,0);
xTransform->setMatrix(xRot);
height = 7.5;
osg::Matrix zTrans = osg::Matrix::translate(0,0,17.5);
osg::Matrix zRot = osg::Matrix::rotate(jointAngle4-M_PI_2, 0,0,1);
osg::MatrixTransform* zTransform = new osg::MatrixTransform();
zTransform->setMatrix(zTrans*zRot);
xTransform->addChild(zTransform);
return zTransform;
}
osg::MatrixTransform* buildTube5(osg::MatrixTransform* previousJoint)
{
double height = 7.5;
double radius = 2.86479;
height = 15.0;
osg::Geode* joint = new osg::Geode();
osg::ShapeDrawable *shape =new osg::ShapeDrawable(new osg::Cylinder(osg::Vec3(0.0f,0.0f,height/2),radius,height),hints);
joint->addDrawable(shape);
osg::MatrixTransform* xTransform = new osg::MatrixTransform();
previousJoint->addChild(xTransform);
xTransform->addChild(joint);
osg::MatrixTransform* zTransform = new osg::MatrixTransform();
osg::Matrix zTrans = osg::Matrix::translate(0,0,height);
zTransform->setMatrix(zTrans);
xTransform->addChild(zTransform);
return zTransform;
}
osg::MatrixTransform* buildJoint5(osg::MatrixTransform* previousJoint)
{
double radius = 2.86479;
double height = 2.86479*2;
osg::Geode* joint = new osg::Geode();
osg::ShapeDrawable *shape = new osg::ShapeDrawable(new osg::Cylinder(osg::Vec3(0.0f,0.0f,0.0f),radius,height),hints);
joint->addDrawable(shape);
osg::MatrixTransform* xTransform = new osg::MatrixTransform();
previousJoint->addChild(xTransform);
osg::Matrix xRot= osg::Matrix::rotate(-M_PI_2, 1.0,0,0);
xTransform->setMatrix(xRot);
xTransform->addChild(joint);
if (showAxis)
{
createAxis(xTransform);
}
osg::MatrixTransform* zTransform = new osg::MatrixTransform();
osg::Matrix zRot= osg::Matrix::rotate(jointAngle5, 0,0,1);
osg::Matrix zTrans = osg::Matrix::translate(0,0,0);
zTransform->setMatrix(zTrans*zRot);
xTransform->addChild(zTransform);
return zTransform;
}
osg::MatrixTransform* buildJoint6(osg::MatrixTransform* previousJoint)
{
double height = 3.0;
double radius = 1.0;
osg::Geode* joint = new osg::Geode();
joint->addDrawable(new osg::ShapeDrawable(new osg::Cylinder(osg::Vec3(0.0f,0.0f,height/2),radius,height),hints));
osg::MatrixTransform* xTransform = new osg::MatrixTransform();
osg::Matrix xRot= osg::Matrix::rotate(M_PI_2, 1.0, 0.0, 0.0);
xTransform->setMatrix(xRot);
xTransform->addChild(joint);
previousJoint->addChild(xTransform);
if (showAxis)
{
createAxis(xTransform);
}
return xTransform;
}
osg::MatrixTransform* buildEndEffector()
{
osg::MatrixTransform* mt = new osg::MatrixTransform();
osg::Matrix m;
double length = 17.0;
m.makeTranslate(0,0,length/2);
mt->setMatrix(m);
osg::Geode *geode_3 = new osg::Geode;
osg::ShapeDrawable *shape1 = new osg::ShapeDrawable(new osg::Box(osg::Vec3(-EndEffector, 0.0f, 0.0f), .5, 1.5f, length), hints);
osg::ShapeDrawable *shape2 = new osg::ShapeDrawable(new osg::Box(osg::Vec3( EndEffector, 0.0f, 0.0f), .5, 1.5f, length), hints);
shape1->setColor(osg::Vec4(0.8f, 0.8f, 0.4f, 1.0f));
shape2->setColor(osg::Vec4(0.8f, 0.8f, 0.4f, 1.0f));
geode_3->addDrawable(shape1);
geode_3->addDrawable(shape2);
mt->addChild(geode_3);
return mt;
}
void createAxis(osg::Transform* previousJoint)
{
double height = 10.0;
double radius = .5;
osg::MatrixTransform* zmt = new osg::MatrixTransform();
previousJoint->addChild(zmt);
osg::ShapeDrawable *zShape = new osg::ShapeDrawable(new osg::Cylinder(osg::Vec3(0.0f,0.0f,height/2),radius,height),hints);
osg::ShapeDrawable *zCone = new osg::ShapeDrawable(new osg::Cone(osg::Vec3(0.0f,0.0f,1.0),radius+1.0,2.0),hints);
osg::MatrixTransform* zmtCone = new osg::MatrixTransform();
osg::Geode *zgCone = new osg::Geode;
zmtCone->setMatrix( osg::Matrix::translate(0.0,0.0,height));
previousJoint->addChild(zmtCone);
zShape->setColor(osg::Vec4(0.0f, 0.0f, 1.0f, 1.0f));
zCone->setColor(osg::Vec4(0.0f, 0.0f, 1.0f, 1.0f));
osg::Geode *z = new osg::Geode;
z->addDrawable(zShape);
zgCone->addDrawable(zCone);
zmtCone->addChild(zgCone);
zmt->addChild(z);
osg::MatrixTransform* mt = new osg::MatrixTransform();
previousJoint->addChild(mt);
osg::Matrix xMatrix = osg::Matrix::rotate(-M_PI_2, 0.0, 1.0, 0.0);
mt->setMatrix(xMatrix);
osg::ShapeDrawable *xShape = new osg::ShapeDrawable(new osg::Cylinder(osg::Vec3(0.0f,0.0f,height/2),radius,height),hints);
xShape->setColor(osg::Vec4(1.0f, 0.0f, 0.0f, 1.0f));
osg::Geode *x = new osg::Geode;
x->addDrawable(xShape);
mt->addChild(x);
osg::MatrixTransform *yMt = new osg::MatrixTransform();
previousJoint->addChild(yMt);
osg::Matrix yMatrix = osg::Matrix::rotate(M_PI_2, 1.0, 0.0, 0.0);
yMt->setMatrix(yMatrix);
osg::ShapeDrawable *yShape = new osg::ShapeDrawable(new osg::Cylinder(osg::Vec3(0.0f,0.0f,height/2),radius,height),hints);
yShape->setColor(osg::Vec4(0.0f, 1.0f, 0.0f, 1.0f));
osg::Geode *y = new osg::Geode;
y->addDrawable(yShape);
yMt->addChild(y);
}
int main(int, char **)
{
hints->setDetailRatio(0.5f);
showAxis = false;
jointAngle1=0.0;
jointAngle2=0.0;
jointAngle3=0.0;
jointAngle4=0.0;
jointAngle5=0.0;
jointAngle6=0.0;
EndEffector=1.0;
osgViewer::Viewer viewer;
viewer.addEventHandler(new KeyboardEventHandler());
// add model to viewer.
viewer.setSceneData( createShapes() );
return viewer.run();
}