Get Rotation of Node

[timmymorris91]

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vector3df v = node->getRotation

I know this gives me the relative poistion but anyway,
the return value only gives me the X and Y rotation but Z always = 0??

If I use a matrix to get absolute transformation and getrotationDegrees I have the same problem.

THE END...
(Not answered)

[vitek]

No, the result of a call to getRotation() will be the relative rotation from the parent node. If you call...

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node->setRotation (core::vector3df (10, 10, 10));

then the result of

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const core::vector3df r = node->getRotation();

should be the vector r with r.x=10, r.y=10, r.z=10. If you don't rotate the node on its Z axis, then you should expect the relative rotation on Z to be 0.

Travis

[timmymorris91]

Im still having a problem.

Node is a gun attached to the camera.

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matrix4 trans =  node->getAbsoluteTranslation();
vector3f v = trans.getRotationDegress();
bullet-setRotation(v);

v should give me the rotation of the gun.
I need the rotation so I can shoot a bullet and use the rotation
as the bullets.

All the rotation works but the Z axis is always the same. If I shoot up, then the bullet will still be flat, not tilted up or down.

[shogun]

This would be the X axis, not the Z axis.

[Eigen]

Actually, wouldn't it be Y? Because in XYZ coordinate system Y is "up/down"

[rogerborg]

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matrix4 trans =  node->getAbsoluteTranslation();
vector3f v = trans.getRotationDegress();
bullet-setRotation(v);

v should give me the rotation of the gun.
I need the rotation so I can shoot a bullet and use the rotation
as the bullets.

All the rotation works but the Z axis is always the same. If I shoot up, then the bullet will still be flat, not tilted up or down.

If you post pseudo-code, then we have to guess what you really meant. I think it was this:

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    ISceneNode * actor = smgr->addEmptySceneNode();
    actor->setRotation(vector3df(10, 20, 30));
    actor->updateAbsolutePosition();

    ISceneNode * gun = smgr->addEmptySceneNode(actor);
    // Presumably the gun doesn't have any rotation of its own
    gun->updateAbsolutePosition();

    matrix4 trans = gun->getAbsoluteTransformation();
    vector3df rotation = trans.getRotationDegrees(); 
    (void)printf("%f %f %f\n", rotation.X, rotation.Y, rotation.Z);

Works For Me.

This would be the X axis, not the Z axis.

Actually, wouldn't it be Y? Because in XYZ coordinate system Y is "up/down"

No. What's returned isn't a direction vector, it's three Euler axis rotations. X axis is pitch.

I imagine that's timmy's issue as well. Unless your nodes are rolled (tilted to the side), the Z rotation will be 0. That's good, as if you're doing your own trig calculations, you really only want to be dealing with rotations in 2 axes, not 3.

I suspect that what you may want is a direction vector for your bullet, not rotations. If so, then you can just use matrix4::rotateVect().

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    ISceneNode * actor = smgr->addEmptySceneNode();
    actor->setRotation(vector3df(45, 90, 0));  // Face right, and 45 degrees up.
    actor->updateAbsolutePosition();

    ISceneNode * gun = smgr->addEmptySceneNode(actor);
    // Presumably the gun doesn't have any rotation of its own
    gun->updateAbsolutePosition();

    matrix4 trans = gun->getAbsoluteTransformation();

    vector3df direction(0, 0, 1);
    trans.rotateVect(direction); 
    direction.normalize();
    (void)printf("%f %f %f\n", direction.X, direction.Y, direction.Z);

[timmymorris91]

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   matrix4 trans = gun->getAbsoluteTransformation(); 
   vector3df rotation = trans.getRotationDegrees(); 
   (void)printf("%f %f %f\n", rotation.X, rotation.Y, rotation.Z); 

I have used this method before.
But when I use the rotation vector and set the bullet being shot to the same direction as the gun, it doesnt apply the right transformation to the bullet.
Maybe It could be the actual model of the bullet, it could be facing towards a different direction.[/code]

[rogerborg]

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   matrix4 trans = gun->getAbsoluteTransformation(); 
   vector3df rotation = trans.getRotationDegrees(); 
   (void)printf("%f %f %f\n", rotation.X, rotation.Y, rotation.Z); 

I have used this method before.
But when I use the rotation vector and set the bullet being shot to the same direction as the gun, it doesnt apply the right transformation to the bullet.

It doesn't apply the transformation that you expect.

How are you using the Euler rotations returned by getRotationDegrees() to produce a direction for the bullet?

[timmymorris91]

I am just setting the rotation of the bullet to the rotation of the gun.

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vector3df rotation = trans->getRotationDegrees();
bullet->setRotation(v);

I would expect that the bullet would face the same direction as the gun.
I dont understand what euler rotations are??

[rogerborg]

Euler angles are described here.

First, you should know about axes and the left hand rule (note that Irrlicht is left handed, not right handed). Get used to the idea of holding up your left hand and twisting it around; you'll be doing it a lot.

The Euler angles just describe 3 rotations around those axes. Irrlicht applies them in 'reverse' order, i.e. Z (roll around your index finger) then Y (yaw around your thumb) then X (pitch around your middle finger).

Now, you can pick any axis to be "forwards", but most people interpret the +Z axis as forwards, i.e. the direction that your index finger is pointing.

Do some pointing around with that finger. Notice how you can point in any direction by first rotating your hand around your thumb (Y rotation) followed by pitching it up or down around your middle finger (X rotation). To "point" your index finger in any direction, you don't have to roll around that finger (a Z rotation).

Did any of that make sense? If not, point, point and point again until you get it.

... all pointed out?

OK, the code you provided looks fine. If trans is the absolute transformation of the gun, then that should (absent issues in the code that we haven't seen) give the bullet the same rotation as the gun. If they aren't pointing in the same directions, check that the models are oriented the same way.

That's half the problem. You also need to create a direction vector for the bullet. You can do this using the rotation angles:

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    // Your code so far
    vector3df rotation = trans->getRotationDegrees();
    bullet->setRotation(rotation);

    // Build a rotation matrix for the direction
    matrix4 rotationMatrix;
    rotationMatrix.setRotationDegrees(rotation);

    // Assume that +Z is forwards
    vector3df bulletDirection(0, 0, 1);

    // Rotate that vector to point in the direction that the bullet is facing
    rotationMatrix.rotateVect(bulletDirection);

    // bulletDirection is the direction in which bulletNode should move