Rotating a 3D coordinate system object

[vishnu-rajeev]

I have created a coordinate system object similar to the one shown in the image. I want to rotate it along all the 3 axes by entering the respective angle entered via a windows forms textbox. I am not able to do this no matter how much I try. Please help. Below is my incomplete and incorrect code. It would be great if someone can correct this and provide guidance.

osg::ref_ptr <osg::Geode> Core::createObjectArrowsTwo()
{
               osg::ref_ptr<osg::Geode> arrowGeode = new osg::Geode;
               //osg::ref_ptr <osg::PositionAttitudeTransform> pat = new osg::PositionAttitudeTransform();

               osg::ref_ptr <osg::PositionAttitudeTransform> xPat = new osg::PositionAttitudeTransform();
               osg::ref_ptr <osg::PositionAttitudeTransform> yPat = new osg::PositionAttitudeTransform();
               osg::ref_ptr <osg::PositionAttitudeTransform> zPat = new osg::PositionAttitudeTransform();

               osg::ref_ptr<osg::Geode> zGeode = new osg::Geode();
               osg::ref_ptr<osg::Cylinder> xCylinder = new osg::Cylinder(osg::Vec3(0., 0., 7.), 0.10, 14.0);
               //xCylinder->setRotation(osg::Quat(osg::DegreesToRadians(90.0), osg::Vec3(0, 1, 0)));
               osg::ref_ptr<osg::ShapeDrawable> xCylinderDrawable = new osg::ShapeDrawable(xCylinder);
               xCylinderDrawable->setColor(osg::Vec4(160.f, 234.f, 142.f, 1.f));
               zGeode->addDrawable(xCylinderDrawable);

               osg::ref_ptr<osg::Cone> xCone = new osg::Cone(osg::Vec3(0.0, 0.0, 14.0), 0.20, 0.8);
               //xCone->setRotation(osg::Quat(osg::DegreesToRadians(90.0), osg::Vec3(0, 1, 0)));
               osg::ref_ptr<osg::ShapeDrawable> xConeDrawable = new osg::ShapeDrawable(xCone);
               xConeDrawable->setColor(osg::Vec4(160.f, 234.f, 142.f, 1.f));
               zGeode->addDrawable(xConeDrawable);

               osg::ref_ptr<osg::Geode> yGeode = new osg::Geode();
               osg::ref_ptr<osg::Cylinder> yCylinder = new osg::Cylinder(osg::Vec3(0., 7., 0.), 0.10, 14.0);
               yCylinder->setRotation(osg::Quat(osg::DegreesToRadians(-90.0), osg::Vec3(1, 0, 0)));
               osg::ref_ptr<osg::ShapeDrawable> yCylinderDrawable = new osg::ShapeDrawable(yCylinder);
               yCylinderDrawable->setColor(osg::Vec4(160.f, 234.f, 142.f, 1.f));
               yGeode->addDrawable(yCylinderDrawable);

               osg::ref_ptr<osg::Cone> yCone = new osg::Cone(osg::Vec3(0.0, 14.0, 0.0), 0.20, 0.8);
               yCone->setRotation(osg::Quat(osg::DegreesToRadians(-90.0), osg::Vec3(1, 0, 0)));
               osg::ref_ptr<osg::ShapeDrawable> yConeDrawable = new osg::ShapeDrawable(yCone);
               yConeDrawable->setColor(osg::Vec4(160.f, 234.f, 142.f, 1.f));
               yGeode->addDrawable(yConeDrawable);

               osg::ref_ptr<osg::Geode> xGeode = new osg::Geode();
               osg::ref_ptr<osg::Cylinder> zCylinder = new osg::Cylinder(osg::Vec3(7., 0., 0.), 0.10, 14.0);
               zCylinder->setRotation(osg::Quat(osg::DegreesToRadians(90.0), osg::Vec3(0, 1, 0)));
               osg::ref_ptr<osg::ShapeDrawable> zCylinderDrawable = new osg::ShapeDrawable(zCylinder);
               zCylinderDrawable->setColor(osg::Vec4(160.f, 234.f, 142.f, 1.f));
               xGeode->addDrawable(zCylinderDrawable);

               osg::ref_ptr<osg::Cone> zCone = new osg::Cone(osg::Vec3(14.0, 0.0, 0.0), 0.20, 0.8);
               zCone->setRotation(osg::Quat(osg::DegreesToRadians(90.0), osg::Vec3(0, 1, 0)));
               osg::ref_ptr<osg::ShapeDrawable> zConeDrawable = new osg::ShapeDrawable(zCone);
               zConeDrawable->setColor(osg::Vec4(160.f, 234.f, 142.f, 1.f));
               xGeode->addDrawable(zConeDrawable);

               xPat->addChild(xGeode);
               yPat->addChild(yGeode);
               zPat->addChild(zGeode);

               arrowGeode->addChild(zPat);
               arrowGeode->addChild(xPat);
               arrowGeode->addChild(yPat);

               _globalSwitch->addChild(arrowGeode);
               return arrowGeode;
}

osg::ref_ptr<osg::Geode> arrows = createObjectArrowsTwo();

osg::Quat zAxisArrowRotationAlongXAxis;
osg::Quat yAxisArrowRotationAlongXAxis;
osg::Quat zAxisArrowRotationAlongYAxis;
osg::Quat xAxisArrowRotationAlongYAxis;
osg::Quat xAxisArrowRotationAlongZAxis;
osg::Quat yAxisArrowRotationAlongZAxis;

osg::Quat xAxisArrowRotationAlongXAxis;
osg::Quat zAxisArrowRotationAlongZAxis;
osg::Quat yAxisArrowRotationAlongYAxis;

double xAxisAngle = 0.0;
double yAxisAngle = 0.0;
double zAxisAngle = 0.0;

System::Void xAxisAngleTextBox_Leave(System::Object^ sender, System::EventArgs^ e)
{
               xAxisAngle = System::Convert::ToDouble(this->xAxisAngleTextBox->Text);

               osg::ref_ptr<osg::PositionAttitudeTransform> arrowTransformZAxis = dynamic_cast<osg::PositionAttitudeTransform*>(arrows->getChild(0));
               osg::ref_ptr<osg::PositionAttitudeTransform> arrowTransformXAxis = dynamic_cast<osg::PositionAttitudeTransform*>(arrows->getChild(1));
               osg::ref_ptr<osg::PositionAttitudeTransform> arrowTransformYAxis = dynamic_cast<osg::PositionAttitudeTransform*>(arrows->getChild(2));

               zAxisArrowRotationAlongXAxis = osg::Quat (osg::DegreesToRadians(xAxisAngle), osg::Vec3d(1, 0, 0));
               arrowTransformZAxis->setAttitude(zAxisArrowRotationAlongXAxis);

               yAxisArrowRotationAlongXAxis = osg::Quat (osg::DegreesToRadians(xAxisAngle), osg::Vec3d(1, 0, 0));
               arrowTransformYAxis->setAttitude(yAxisArrowRotationAlongXAxis);
}

System::Void yAxisAngleTextBox_Leave(System::Object^ sender, System::EventArgs^ e)
{
               yAxisAngle = System::Convert::ToDouble(this->yAxisAngleTextBox->Text);

               osg::ref_ptr<osg::PositionAttitudeTransform> arrowTransformZAxis = dynamic_cast<osg::PositionAttitudeTransform*>(arrows->getChild(0));
               osg::ref_ptr<osg::PositionAttitudeTransform> arrowTransformXAxis = dynamic_cast<osg::PositionAttitudeTransform*>(arrows->getChild(1));
               osg::ref_ptr<osg::PositionAttitudeTransform> arrowTransformYAxis = dynamic_cast<osg::PositionAttitudeTransform*>(arrows->getChild(2));

               zAxisArrowRotationAlongYAxis = osg::Quat (osg::DegreesToRadians(yAxisAngle), osg::Vec3d(0, 1, 0));
               arrowTransformZAxis->setAttitude(zAxisArrowRotationAlongYAxis * zAxisArrowRotationAlongXAxis);

               xAxisArrowRotationAlongYAxis = osg::Quat (osg::DegreesToRadians(yAxisAngle), osg::Vec3d(0, 1, 0));
               xAxisArrowRotationAlongXAxis = osg::Quat (osg::DegreesToRadians(xAxisAngle), osg::Vec3d(1, 0, 0));
               arrowTransformXAxis->setAttitude(xAxisArrowRotationAlongYAxis * xAxisArrowRotationAlongXAxis);
}

System::Void zAxisAngleTextBox_Leave(System::Object^ sender, System::EventArgs^ e)
{
               zAxisAngle = System::Convert::ToDouble(this->zAxisAngleTextBox->Text);

               osg::ref_ptr<osg::PositionAttitudeTransform> arrowTransformZAxis = dynamic_cast<osg::PositionAttitudeTransform*>(arrows->getChild(0));
               osg::ref_ptr<osg::PositionAttitudeTransform> arrowTransformXAxis = dynamic_cast<osg::PositionAttitudeTransform*>(arrows->getChild(1));
               osg::ref_ptr<osg::PositionAttitudeTransform> arrowTransformYAxis = dynamic_cast<osg::PositionAttitudeTransform*>(arrows->getChild(2));

               xAxisArrowRotationAlongZAxis = osg::Quat (osg::DegreesToRadians(zAxisAngle), osg::Vec3(0, 0, 1));
               arrowTransformXAxis->setAttitude(xAxisArrowRotationAlongYAxis * xAxisArrowRotationAlongZAxis);

               yAxisArrowRotationAlongZAxis = osg::Quat (osg::DegreesToRadians(zAxisAngle), osg::Vec3(0, 0, 1));
               arrowTransformYAxis->setAttitude(yAxisArrowRotationAlongXAxis * yAxisArrowRotationAlongZAxis);
}

[robertosfield]

I haven't closely stepped through your code but on a quick scan you are misusing vsg::Geode. vsg::Geode is a hang up from early days in the OSG project when you couldn't add drawables/geometry to group nodes. "Modern" OSG allows you to add drawables to osg::Group so it's the osg::Geode is no longer required, As part of these changes Geode all got the ability to add children beyond drawables but that only happened to keep the API glue backwards compatibility.

What you should be doing in your code is just using a osg::Group where you are specifying a osg::Geode. I don't know if this will fix the problem but it will take you one step closer to having cleaner code.

As a general comment I'd just use a single transform above the axis arrows and just create the arrows pointing along the appropriate axis.

If you are new to the OSG so just learning this stuff for the first time then please take a look at VulkanSceneGraph, it's the successor to the OSG and a far more modern and future-proofed API. While the OSG, like OpenGL, is now just in maintenance mode.

[vishnu-rajeev]

I am using openscenegraph as part of my work. I am not sure if the OSG version I am using at work is "Modern" OSG. But I will try changing Geode to Group and see. I want to rotate the coordinate system object along the x, y and z axis. For example if I rotate along x axis then the x arrow should remain fixed and the other 2 arrows should rotate along x axis. This is the reason I used separate transforms. At first I did try using a single transform and added the x, y and z geodes to it. But it did not work properly. I think that the problem is that I am not setting the attitudes to the correct values (especially when I am combining rotations, for example rotating along x axis and then rotating the rotated object again along another axis and so on). But I am not figure out what I am doing wrong. I am still in beginner in OSG so it would be great if you could look at the code and correct the mistake I am making. Or atleast guide me in the right direction.

[AnyOldName3]

This could be the classic gimbal lock problem you get with (mis)using Euler Angles. Things are almost certainly going to be easier if you have one quaternion that represents the whole rotation and use that for a single transform, whether that comes from combining separate quaternions into one, constructing one directly using one of the functions that takes several angles and axes, or by just googling how to convert Euler Angles to a quaternion and setting the quaternion components explicitly.