### Author Topic: Troubles with rotation matrix  (Read 1477 times)

#### rtSJ

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• Posts: 21
##### Troubles with rotation matrix
« on: May 16, 2014, 02:06:32 pm »
Hello everyone !

I write it today because I have a problem with the orientation of a jPCT camera. I use the sensor of the device to do augmented reality. I use this tutorial to get the differents values [http://www.thousand-thoughts.com/2012/03/android-sensor-fusion-tutorial/] (Because the easy way is too noisy). I get a rotation matrix and 3 angles (Pitch, roll and Azimuth).

So I want to use the 3 angles with a simple rotateCameraAxis. But I can't because the 3 values ar not independant and when I rotate on 1 axis, others moves and I can't rotate for the 2 others. (I you have a solution, say it, I'm happy to read it !)

The second way to rotate the camera is to use the rotation matrix. I convert it to a 4x4 matrix and fill with 0 and one 1, I base it on cols. But it don't work. And more, my view is totally deformed. My modles are very stranges... Anyone have a solution about it ?

How can I use the 3 angles or the matrix to rotate my camera ?

Thanks !
« Last Edit: May 23, 2014, 09:34:33 am by rtSJ »

#### Aksiom

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• Posts: 3
##### Re: Troubles with rotation matrix
« Reply #1 on: May 16, 2014, 02:12:05 pm »
Hi if I get it right you may want t oread my question on StackOverflow.

http://stackoverflow.com/questions/23683150/rotation-vector-sensor-reverse-the-horizontal-rotation

I have found a solution to my question but I couldnt answer it yet because StackOverflow is in read only mode today. So if this is what you are looking for then let me know I will write the solution here.

Hope it helps.

#### rtSJ

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• Posts: 21
##### Re: Troubles with rotation matrix
« Reply #2 on: May 16, 2014, 02:45:22 pm »
Thanks for your answer, but it's not what I look for... Sorry ^^'

#### EgonOlsen

• Posts: 11899
##### Re: Troubles with rotation matrix
« Reply #3 on: May 18, 2014, 02:34:06 pm »
The best approach is to use the rotation matrix. Keep jPCT's coordinate system in mind: http://www.jpct.net/wiki/index.php/Coordinate_system as well as the fact that jPCT's matrices are row major.

« Last Edit: May 19, 2014, 02:06:13 pm by EgonOlsen »

#### rtSJ

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• Posts: 21
##### Re: Troubles with rotation matrix
« Reply #4 on: May 19, 2014, 01:52:07 pm »
Okay, I understand but what is weird is when I apply ma matrix on my camera, the view is deformed. And the camera is not oriented correctly, I'm sur.

When I get the matrix data, I transform it to a 4x4 matrix and I dump to the matrix of the camera :

Code: [Select]
`gyroMatrix = getRotationMatrixFromOrientation(fusedOrientation);                        float[] arr4x4 = new float[16];            for(int i = 0; i < 9; i++){    arr4x4[i] = gyroMatrix[i];}arr4x4[3] = 0;arr4x4[7] = 0;arr4x4[11] = 0;arr4x4[12] = 0;arr4x4[13] = 0;arr4x4[14] = 0;arr4x4[15] = 1;            scene.xyzMatrix.setDump(arr4x4);`
And in my cycle of rendering I update the camera with :

Code: [Select]
`Camera worldcam = world.getCamera(); worldcam.setBack(xyzMatrix);`
I don't understand what I doing wrong because I think I do everything good...

#### EgonOlsen

• Posts: 11899
##### Re: Troubles with rotation matrix
« Reply #5 on: May 19, 2014, 02:13:40 pm »
... I think I do everything good...
No, you don't...apart from different coordinate systems and the missing conversion between them, your matrix filling is wrong. You copy the 9 elements of the source matrix into the first 9 elements of the target matrix, but it should actually be
• =[0], [1]=[1], [2]=[2], [4]=[3]...your code ignores the fact that the last row and column in the target matrix are not present in the source matrix.

#### rtSJ

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• Posts: 21
##### Re: Troubles with rotation matrix
« Reply #6 on: May 19, 2014, 03:47:08 pm »
Okay, okay It's my fault, I'm sorry. It's work quite well. Thank you ! I'm not very familiar with the 3D mathematics.

Concerning the different coordinate systems and the conversion between them, I make a rotation of the matrix with this line of code :

Code: [Select]
`rotationMatrix = matrixMultiplication(rotationMatrix, myXDegRotationMatrix);`
But I'm not sur of what matrix I'm suppose to use. I try to do a rotation of 180 degree with :

Code: [Select]
`my180DegRotationMatrix[0] = 1.0f; my180DegRotationMatrix[1] = 0.0f; my180DegRotationMatrix[2] = 0.0f;my180DegRotationMatrix[3] = 0.0f; my180DegRotationMatrix[4] = -1.0f; my180DegRotationMatrix[5] = 0.0f;my180DegRotationMatrix[6] = 0.0f; my180DegRotationMatrix[7] = 0.0f; my180DegRotationMatrix[8] = -1.0f;`
And a rotation of 90 degree anti-clockwise :

Code: [Select]
`my90DegRotationMatrix[0] = 1.0f; my90DegRotationMatrix[1] = 0.0f; my90DegRotationMatrix[2] = 0.0f;my90DegRotationMatrix[3] = 0.0f; my90DegRotationMatrix[4] = 0.0f; my90DegRotationMatrix[5] = 1.0f;my90DegRotationMatrix[6] = 0.0f; my90DegRotationMatrix[7] = -1.0f; my90DegRotationMatrix[8] = 0.0f;`
But that didn't works