Spatial disappears when I move it

#21

Open JME (I am using stable version 3.1) and blender (preferably with the same model that was loaded by your game, in my case the “valet2”).

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In 3D-View, press “n” to open the properties tab of the selected object (Sorry if I made a mistake in the name of this tab).
Note that the location, scale, and rotation property exists. In the case let’s focus on the rotation (of course :))!

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In rotation, there exists the x, y, z axis. (Assume that the z axis of the blender is the y axis of the JME), there is a space with some options (As shown in arrow 1), select the Quartenion option ).

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Note that a fourth axis, the “w”, has now appeared. Now the axes of the blender corresponds to the axis of the JME (Again, the z axis of the blender is the y axis of the JME).

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Now, press “7” or go View → Top, to be in the top view. Select the model and press “r”, so you can rotate the object. To get more precise, after pressing “r” type “90”, for your model to be 90 °. Now notice how the values of the axes (x, y, z, w) remained.

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Now in JME, change the rotation by entering the values you got in the blender (Again, the z axis of the blender is the y axis of the JME).

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And order … note that the rotation was done successfully!

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2 Likes
#22

If you just want to create a quaternion which represents rotation for X degrees around for example Y axis, you can get one by calling:
new Quaternion().fromAngleAxis() which accepts a rotation axis and a rotation in degrees.

Btw for more experienced people, why is fromAngleAxis() not static? Why do I have to create a throwaway quaternion just to make another one?

#23

Cause it invokes fromAngleNormalAxis() which is not static? And it is not static because you have to create instance somewhere not touching reference Quaternion()? (I assume)

#24

You’re not making a throwaway one though, the one you create is the one the rotation gets applied to. It’s a local method.

#25

To OP, if you find yourself setting quaternion values directly then you are doing something wrong.

Unless you happen to be writing low-level serialization code… you’ve made a bunch of bad choices and a bunch of bad assumptions.

#26

Have you tried instead to apply the rotation in blender before importing in JME3? (Object -> Apply -> Rotation).

#27

Why does it return the quaternion then?
Something confusing is going on here.

#28

No it’s pretty much as it should be. Most Vector3f and Quaternion methods return the object for easy chaining of method calls iirc, which is quite useful all the time.

#29

Exactly…

fromAngles() returns “this” so that you can easily chain things.

fromAngles() is not static so that you can avoid creating a throw-away Quaternion if you already have one… and it follows the pattern already set by a hundred other methods.

#30

because it is:

protected float x, y, z, w;

then

public Quaternion() {
        x = 0;
        y = 0;
        z = 0;
        w = 1;
}

then

public Quaternion fromAngleNormalAxis(float angle, Vector3f axis) {
        if (axis.x == 0 && axis.y == 0 && axis.z == 0) {
            loadIdentity();
        } else {
            float halfAngle = 0.5f * angle;
            float sin = FastMath.sin(halfAngle);
            w = FastMath.cos(halfAngle);
            x = sin * axis.x;
            y = sin * axis.y;
            z = sin * axis.z;
        }
        return this;
}
#31

@oreganBR you seriously need to see this and this. Don’t touch the Quaternions. You can (and I believe you should) rotate your models as in real life: degrees or radians. I never create Quaternionx like you do in the code.

#32

Sorry happened too many problems (usb cable, internet 3g).

#33

I will try this method …

#34

For me? I had no idea I was doing something so wrong … The best way would be this: