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# Get Pitch, Yall and Roll from matRotation

## 6 posts in this topic

D3DXMATRIX matRotation;

How can I get Pitch, Yaw and Roll values from matRotation? Edited by Medo3337
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This routine served me well (the one time I used it), always be careful with these three angles, usually it ends up in tears and gimbal locks:

[code]
void ToEulerAngles( float& fAngleX, float& fAngleY, float& fAngleZ )
{
static float fRadiansToDegree = 180.0f / 3.1415926f;
fAngleY = asinf( M[8] ); // Calculate Y-axis angle
float fCY = cosf( fAngleY );
if ( fabsf( fCY ) > 0.005f )
{
float ftrx = M[10] / fCY; // No, so get X-axis angle
float ftry = -M[9] / fCY;
fAngleX = atan2f( ftry, ftrx ) * fRadiansToDegree;
ftrx = M[0] / fCY; // Get Z-axis angle
ftry = -M[4] / fCY;
fAngleZ = atan2f( ftry, ftrx ) * fRadiansToDegree;
}
else
{
// Gimbal lock?
fAngleX = 0; // Set X-axis angle to zero
float ftrx = M[5]; // And calculate Z-axis angle
float ftry = M[1];
fAngleZ = atan2f( ftry, ftrx ) * fRadiansToDegree;
}
if ( fAngleX < 0 )
{
fAngleX += 360;
}
if ( fAngleY < 0 )
{
fAngleY += 360;
}
if ( fAngleZ < 0 )
{
fAngleZ += 360;
}
}
[/code]

The routine is a member of a 4x4 matrix with these members:

[code]
struct tStruct
{
float _11, _12, _13, _14;
float _21, _22, _23, _24;
float _31, _32, _33, _34;
float _41, _42, _43, _44;
};

union
{
tStruct ms;
float m[4][4];
float M[16];
};
[/code] Edited by Endurion
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How do you use this method with
[left][background=rgb(250, 251, 252)]matRotation?[/background][/left]

[left][size=4][color=#282828][font=helvetica, arial, verdana, tahoma, sans-serif][background=rgb(250, 251, 252)]The method I want is to be able to pass [/background][/font][/color][color=#282828][font=helvetica, arial, verdana, tahoma, sans-serif][background=rgb(250, 251, 252)]matRotation which is "D3DXMATRIX" and get the rotation X, Y and Z.[/background][/font][/color][/size][/left]

[b]Remember, I want the EXACT values of Pitch, Yaw and Roll from [color=#282828][font=helvetica, arial, verdana, tahoma, sans-serif][left][background=rgb(250, 251, 252)]D3DXMATRIX.[/background][/left][/font][/color][/b] Edited by Medo3337
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A D3DXMATRIX has these members:

typedef struct _D3DMATRIX {
union {
struct {
float _11, _12, _13, _14;
float _21, _22, _23, _24;
float _31, _32, _33, _34;
float _41, _42, _43, _44;

};
float m[4][4];
};
} D3DMATRIX;

You can map all the M[x] accesses to m[x][y], you just need to use the right order of columns/rows.
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Here's what I use:
http://www.euclideanspace.com/maths/geometry/rotations/conversions/matrixToEuler/
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I see some issues stated about converting matrix to Euler, I want to guarantee that I will receive VALID values and EXACTLY the same rotation values from a D3DXMATRIX every time I convert D3DXMATRIX to Euler without any problem, is that possible?
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[quote name='Medo3337' timestamp='1337590649' post='4941866']
I see some issues stated about converting matrix to Euler, I want to guarantee that I will receive VALID values and EXACTLY the same rotation values from a D3DXMATRIX every time I convert D3DXMATRIX to Euler without any problem, is that possible?
[/quote]

Barring rounding errors, you'll get the exact same rotation in euler angles. However, euler angles do not represent orientations uniquely, meaning there's more than one set of euler angles for any given orientation.

Of course, as long you'll use the same algorithm for conversion, matrix M will always give the same angles X, Y and Z. But, for instance, if your rotate M by 45 degrees around the Y axis, you won't necessarily get X, Y+45 and Z. Just another set of angles that represent that orientation.

So, if you want to keep the exact euler values, e.g. as entered, you have to save them...
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