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# Trig Rotation

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Need a little help with trig rotation following the website below:
http://www.kirupa.com/developer/actionscript/trig_multiple_axis.htm

For whatever reason, rotating around the center of the object using certain angles result in a flattening of the object.
Everything works good with two different axes rotations, but upon the introduction of the third, there's trouble.
If you have a solution, it has to be something simple I'm sure, any source would be much appreciated.

Thanks.

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Usually, any standard photo/image viewing software, such as the Windows Photo Gallery, will allow you to rotate an image by varying degrees. I believe you can right click the image in question and then select rotate clockwise/counter clockwise for the desired effect, and there is likely a way to adjust the exact degree you want to rotate by changing some options, but I don't know them off hand (Google). Hope this helped!

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Need a little help with trig rotation following the website below:
http://www.kirupa.com/developer/actionscript/trig_multiple_axis.htm

For whatever reason, rotating around the center of the object using certain angles result in a flattening of the object.
Everything works good with two different axes rotations, but upon the introduction of the third, there's trouble.
If you have a solution, it has to be something simple I'm sure, any source would be much appreciated.

Thanks.

Sounds like the problem could be due to Gimbal Lock .

You may be able to implement your three dimensional rotations as a matrix/quaternion instead of using Euler angles to solve this problem (if it is the problem I think it is). Do you have any screenshots/demo you could share?

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[quote name='oblivion_ocean' timestamp='1310840077' post='4836072']
Need a little help with trig rotation following the website below:
http://www.kirupa.com/developer/actionscript/trig_multiple_axis.htm

For whatever reason, rotating around the center of the object using certain angles result in a flattening of the object.
Everything works good with two different axes rotations, but upon the introduction of the third, there's trouble.
If you have a solution, it has to be something simple I'm sure, any source would be much appreciated.

Thanks.

Sounds like the problem could be due to Gimbal Lock .

You may be able to implement your three dimensional rotations as a matrix/quaternion instead of using Euler angles to solve this problem (if it is the problem I think it is). Do you have any screenshots/demo you could share?
[/quote]
Thanks for your quick response!

If you could link me to some matrix/quaternion source that would be great, but using Euler angles is an attempt to keep things straight-forward.
I will definitely get some screenshots or make a small video illustrating the problem later this evening.

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[quote name='oblivion_ocean' timestamp='1310840077' post='4836072']
Need a little help with trig rotation following the website below:
http://www.kirupa.com/developer/actionscript/trig_multiple_axis.htm

For whatever reason, rotating around the center of the object using certain angles result in a flattening of the object.
Everything works good with two different axes rotations, but upon the introduction of the third, there's trouble.
If you have a solution, it has to be something simple I'm sure, any source would be much appreciated.

Thanks.

Sounds like the problem could be due to Gimbal Lock .

You may be able to implement your three dimensional rotations as a matrix/quaternion instead of using Euler angles to solve this problem (if it is the problem I think it is). Do you have any screenshots/demo you could share?
[/quote]
Thanks for your quick response!

If you could link me to some matrix/quaternion source that would be great, but using Euler angles is an attempt to keep things straight-forward.
I will definitely get some screenshots or make a small video illustrating the problem later this evening.

Thanks again.

[/quote]

Could you use something like: Matrix3D?

there is also: Adobe ActionScript 3.0 * Working in three dimensions

An example given from that link:

 package { import flash.display.Sprite; import flash.display.Shape; import flash.display.Graphics; import flash.geom.*; public class Matrix3DTransformsExample extends Sprite { private var rect1:Shape; private var rect2:Shape; public function Matrix3DTransformsExample():void { var pp:PerspectiveProjection = this.transform.perspectiveProjection; pp.projectionCenter = new Point(275,200); this.transform.perspectiveProjection = pp; rect1 = new Shape(); rect1.x = -70; rect1.y = -40; rect1.z = 0; rect1.graphics.beginFill(0xFF8800); rect1.graphics.drawRect(0,0,50,80); rect1.graphics.endFill(); addChild(rect1); rect2 = new Shape(); rect2.x = 20; rect2.y = -40; rect2.z = 0; rect2.graphics.beginFill(0xFF0088); rect2.graphics.drawRect(0,0,50,80); rect2.graphics.endFill(); addChild(rect2); doTransforms(); } private function doTransforms():void { rect1.rotationX = 15; rect1.scaleX = 1.2; rect1.x += 100; rect1.y += 50; rect1.rotationZ = 10; var matrix:Matrix3D = rect2.transform.matrix3D; matrix.appendRotation(15, Vector3D.X_AXIS); matrix.appendScale(1.2, 1, 1); matrix.appendTranslation(100, 50, 0); matrix.appendRotation(10, Vector3D.Z_AXIS); rect2.transform.matrix3D = matrix; } } } 

Hope it helps!

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Thanks for the post, do you have it in C though?

It did happen again just now so, it's definitely something and it turned my 2D box into what looks like a toothpick.
I do think it is that Gimbal lock, which should be fine as long as it's rare and this does seem more difficult to replicate.
I am still playing with this, I'll let you know though ..and yes, C source if you have it, would be great.

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Thanks for the post, do you have it in C though?

It did happen again just now so, it's definitely something and it turned my 2D box into what looks like a toothpick.
I do think it is that Gimbal lock, which should be fine as long as it's rare and this does seem more difficult to replicate.
I am still playing with this, I'll let you know though ..and yes, C source if you have it, would be great.

Maybe this?

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[font=arial, verdana, tahoma, sans-serif][size=2]I can't imagine how gimbal lock can possibly result in flattening of the object. Perhaps you can post some of your code?[/font]

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Okay, I'll keep it simple and illustrate 2 formulas.
This formula works great, only thing is it's just 2 axis rotations.

mw.new_x = cos(degy)* x + sin(degy)*sin(degx)*y - sin(degy)*cos(degx)*z;
mw.new_y = 0 + cos(degx)*y + sin(degx)*z;
mw.new_z = sin(degy)*x + cos(degy)*-sin(degx) *y + cos(degy)*cos(degx)*z;
[/quote]

This is the one from the website (adjusted a bit) perhaps I'm implementing it wrong?
After I used a cube illustration, it's apparent gimbal lock isn't the problem.

mw.new_y = cos(anglex)*y - sin(anglex)*z;
mw.new_z = sin(anglex)*y + cos(anglex)*z;

mw.new_z = cos(angley)*mw.new_z - sin(angley)*x;
mw.new_x = sin(angley)*mw.new_z + cos(angley)*x;

mw.new_x = cos(anglez)*mw.new_x - sin(anglez)*mw.new_y;
mw.new_y = sin(anglez)*mw.new_x + cos(anglez)*mw.new_y;
[/quote]

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Gimbal lock may appear when performing several consecutive rotations. It means especially that, also performing 3 rotations, the 3rd rotation has no effect that could not be done with the 1st rotation already. So1. gimbal lock cannot be responsible for shape flattening, and
2. using matrices or quaternions doesn't prevent from gimbal lock.

The link in the OP doesn't work, so I haven't seen the effect on the shape. However, "flattening the object" sounds like scaling or perhaps shearing effect. That may happen in case that the coefficients of the rotation matrix are not set as is needed for pure rotations.

Furthermore, shape distortions will happen also simply when just enough consecutive rotations are performed. This is because of numerical inaccuracies. We are speaking of a few dozen matrix rotations and even more quaternion rotations. Hence I don't assume that the OP is based on this kind of problem, because the problem sounds to happen immediately with the 3rd partial rotation.

So could we get some code snippet to check?

EDIT: A more detailed post was made just during I wrote this answer. So please be patient ...

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