### Author Topic: eulerToAxis / axisToEuler  (Read 24380 times)

Here is a nifty set of functions for use in converting between Euler and axis angles.

The basic usage for eulerToAxis() is this:

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`%obj.setTransform(%position SPC eulerToAxis(%x SPC %y SPC %z));`
Note: Using eulerToMatrix() in the example above produces incorrect results.

The basic usage for axisToEuler() is this:

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`%eulerRot = axisToEuler(getWords(%obj.getTransform(),3,6));`
Note: Do not use axisToEuler() with %obj.rotation, as it produces incorrect results.

Now for the code:

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`function eulerToAxis(%euler){ %euler = VectorScale(%euler,\$pi / 180); %matrix = MatrixCreateFromEuler(%euler); return getWords(%matrix,3,6);}function axisToEuler(%axis){ %angleOver2 = getWord(%axis,3) * 0.5; %angleOver2 = -%angleOver2; %sinThetaOver2 = mSin(%angleOver2); %cosThetaOver2 = mCos(%angleOver2); %q0 = %cosThetaOver2; %q1 = getWord(%axis,0) * %sinThetaOver2; %q2 = getWord(%axis,1) * %sinThetaOver2; %q3 = getWord(%axis,2) * %sinThetaOver2; %q0q0 = %q0 * %q0; %q1q2 = %q1 * %q2; %q0q3 = %q0 * %q3; %q1q3 = %q1 * %q3; %q0q2 = %q0 * %q2; %q2q2 = %q2 * %q2; %q2q3 = %q2 * %q3; %q0q1 = %q0 * %q1; %q3q3 = %q3 * %q3; %m13 = 2.0 * (%q1q3 - %q0q2); %m21 = 2.0 * (%q1q2 - %q0q3); %m22 = 2.0 * %q0q0 - 1.0 + 2.0 * %q2q2; %m23 = 2.0 * (%q2q3 + %q0q1); %m33 = 2.0 * %q0q0 - 1.0 + 2.0 * %q3q3; return mRadToDeg(mAsin(%m23)) SPC mRadToDeg(mAtan(-%m13, %m33)) SPC mRadToDeg(mAtan(-%m21, %m22));}`
« Last Edit: October 28, 2015, 11:04:38 AM by Badspot »

#### Marcem

Is this used for rotation based on angles and stuff?

Rotation in Blockland (Torque) uses axis angles instead of 0 to 360-degree Euler angles for rotation.

If you want to rotate an object 90 degrees on the Z axis, you'd use this:

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`%obj.setTransform(%position SPC eulerToAxis("0 0 90");`
Now, if you have an object and you want to find out what it's rotation is in "normal" (Euler) degrees, you'd use this:

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`%eulerRot = axisToEuler(getWords(%obj.getTransform(),3,6));`
So, these two functions are very useful when dealing with physical objects in Blockland (Torque).
« Last Edit: December 28, 2007, 06:23:14 PM by Trader »

#### Marcem

Thats awesome. I may need to use this.

#### Randy

Thanks, I've been looking for quatToEuler for a while.

Me as well.  No problem.
« Last Edit: December 28, 2007, 06:23:55 PM by Trader »

#### exidyne

Same thing, smushed to three lines:

Code: [Select]
`function mEulerToQuat(%euler) {   %euler = VectorScale(%euler, 0.017453);   %matrix = MatrixCreateFromEuler(%euler);   return getWords(%matrix, 3, 6);}`

Yeah, I'm not taking credit for writing these functions.  The first is an edit of a function posted by Badspot on the GarageGames forums, the second is an edit of a function posted by another GarageGames forum member.  Anyway, change made and I took off a couple lines on the second function as well.
« Last Edit: December 28, 2007, 06:24:24 PM by Trader »

Not too long ago at a bar during IGC, the topic of quaternions came up and I was informed by my enebriated peers that what I was explaining as a quaternion was actually an Axis Angle and a quaternion was something entirely more complex like a double ended 4 dimensional cone with a spherical base (you can see this by how scary the quaternion wiki page looks compared to the axis angle page).

Ah, I see.  I changed my posts above to reflect your correction.  Thanks for the sticky.

#### Loopyla1

I cant understand a WORD of coding. I shouldn't be here.

#### BobAndRob

Useful on many occasions, thanks Trader.
« Last Edit: August 27, 2009, 06:04:13 PM by BobAndRob »

#### Loopyla1

loopyla1, if you think you shouldn't be here, than DO NOT COME to post that you should not be posting, i know  you are new, but posting random _ to get your post count up is not the way to have people like you, it is a way to get yourself banned and annoy people.
Go away.

Not too long ago at a bar during IGC, the topic of quaternions came up and I was informed by my enebriated peers that what I was explaining as a quaternion was actually an Axis Angle and a quaternion was something entirely more complex like a double ended 4 dimensional cone with a spherical base (you can see this by how scary the quaternion wiki page looks compared to the axis angle page).
Your post made me look at the quaternion page...
HAVE MERCY ON MY SOUL!!!!

#### Deep2

Your post made me look at the quaternion page...
HAVE MERCY ON MY SOUL!!!!

I did the same thing before I read your post, :D

I was like holy stuff! Theres a fourth dimension in space?