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Roll, Pitch, and Yaw of a camera

by Nathan Bowhay - ESAL · in Torque 3D Professional · 08/23/2011 (4:12 pm) · 4 replies

I am trying to get the roll pitch and yaw of a camera. I have managed to get the pitch and yaw by simply doing this:
%transform = %camera.getTransform();
%AngleAxis = getWords(%transform, 3);
%AngleAxis = setWord(%AngleAxis, 3, mRadToDeg(getWord(%AngleAxis, 3)));
%rot = AngleAxisToPitchYaw(%AngleAxis);

Since the transform has the angle in angle axis form, I just needed to use the conversion function.

I also needed to look at the yaw and if it was greater than 180 multiply the pitch by -1 because for some reason it flips and I want absolute roll pitch yaw.

So that gives me yaw and pitch, but how do I get roll?

At first I thought that Euler was the same as Yaw Pitch Roll, but it seems that AngleAxisToEuler gives me rotations on axis when it doesn't appear there is any rotation.

I also found this: sunday-lab.blogspot.com/2008/04/get-pitch-yaw-roll-from-quaternion.html and tried using it so I just used the Quaternion ctor to convert from angle axis to quaternion and then to yaw, pitch roll, but again the rotations seemed to be off.

I also found www.garagegames.com/community/forums/viewthread/59072 , but the function seems to take 2 args for mAtan and only one for mSqrt.

Hopefully some can shed some light on on all this.
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Associate Chris Haigler
Jester Dance
#1
08/23/2011 (11:39 pm)
Just a quick attempt at T3D-ifying the GetEulerAngles function. It'll compile and return a Euler but I'm really not sure if the math is correct. 

DefineEngineFunction( GetEulerAngles, EulerF, (Point3F pos1, AngAxisF aa1),, "Retrieves Euler from transformation matrix." )
{
	MatrixF objTx(true);
	aa1.setMatrix(&objTx);
	objTx.setColumn(3, pos1);

	VectorF vec;
	objTx.getColumn(1, &vec);

	Point3F xv;
	objTx.getColumn(0, &xv);

   Point3F rot(-mAtan2(vec.z, mSqrt(vec.x*vec.x + vec.y*vec.y)), mDot(xv,Point3F(0,0,1)), -mAtan2(-vec.x,vec.y) );        
 
   F32 pitch = mRadToDeg(rot.x);    
   F32 yaw = mRadToDeg(rot.z);     
   F32 roll = mRadToDeg(rot.y); 
  
	Point3F ret(pitch, (yaw + 180.0f), roll);

	return ret;
}

Usage will be something like: GetEulerAngles(<objectId>.position, <objectId>.rotation);

Torque 3D Owner Nathan Bowhay - ESAL
ESALPllc
#2
08/25/2011 (11:53 am)
Yeah that doesn't get the correct roll either, hmm. If anyone knows how to get the local roll rotation that would be awesome. I really need to brush up on rotations.

Torque 3D Owner Nathan Bowhay - ESAL
ESALPllc
#3
09/27/2011 (3:54 pm)
I also posted on gamedev with some more info: www.gamedev.net/topic/609224-roll-pitch-yaw-rotation-from-angle-axis/page__view_...

Torque 3D Owner Nathan Bowhay - ESAL
ESALPllc
#4
11/08/2011 (11:20 am)
Ok I think I got the function converted correctly and it works, not sure how much different it is then what Cris said, Maybe I messed something up the first time.

DefineConsoleFunction( TransformToRollPitchYaw, Point3F, ( TransformF trans),,
   "@brief Converts the transform's rotation to Roll, Pitch, Yaw.\n\n"
   "@param trans Transform to be converted.\n"
   "@return Roll, Pitch, and Yaw as a Point3F.\n"
   "@ingroup Math" )
{
	// Get current object transform matrix  
	MatrixF objTx = trans.getMatrix();

	// Get rotations from transform matrix  
	VectorF vec;  
	objTx.getColumn(1,&vec);  

	// Get X-vector for roll calculation  
	Point3F xv;  
	objTx.getColumn(0,&xv);  

	// Calculate PRH (x = pitch, y = roll, z = heading)  
	Point3F rot(-mAtan2(vec.z, mSqrt(vec.x*vec.x + vec.y*vec.y)), mDot(xv,Point3F(0,0,1)), -mAtan2(-vec.x,vec.y) );  

	// Set up vars  
	F32 pitch = mRadToDeg(rot.x);     // Pitch  
	F32 yaw = mRadToDeg(rot.z);       // Heading  
	F32 roll = mRadToDeg(rot.y);      // Roll  

	return Point3F(roll, pitch, yaw);
}