Assistance needed with NAN

[Sundar0206]

Hi all

Yet another question from me and hope some one shoots the answer immediately.. very simple though

I have been tryin to do a rigid body simulation ... things work fine until i hit a nan ..

What I am trying to do is retrieve a angle from a quaternion for which i wrote this following function...

void get_AxisAngle_from_Quat(float &angle, Xlib::vec3d &axis) 
{

float squareLength = get4d_X()*get4d_X() + get4d_Y()*get4d_Y() + get4d_Z()*get4d_Z();

					
						

if (squareLength>C_EPSILON)
{
angle = 2.0f * (float) acos(get4d_Z());
//assert (!XlibMath::is__nan(angle));
float inverseLength ;
inverseLength = 1.0f /  (float) pow(squareLength, 0.5f) ;
axis.x = get4d_X() * inverseLength;
axis.y = get4d_Y() * inverseLength;
axis.z = get4d_Z() * inverseLength;
	}
else
{
 angle = 0.0f;
 axis.x = 1.0f;
 axis.y = 0.0f;
 axis.z = 0.0f;
}
}

This is being refered in the code by this way

        Xlib::vec3d axis(1,0,0);
	float angle=0.0f;
	
	RBody[0].q.get_AxisAngle_from_Quat(angle,axis);
	
	Xlib::DevMsg("Quat  ",RBody[0].q);
	Xlib::DevMsg("Angle ", 	angle);

but This hits a nan and everytime it hits nan my object disappears from the screen.... (DevMsg is a overload for cout i use) When i try printing out the values at the point where i hit the nan this shows this

DevMsg: Quat   1.442195 0.698514 1.700220 0.403262
Angle  nan

I read online but it states nan is got by dividing by 0 .. but clearly i am not using any divisions at al...

can someone clarify me on where i went wrong ????

Cheers and regards

[firedraco]

I'm guessing it's here:

angle = 2.0f * (float) acos(get4d_Z());

Make sure that get4d_Z() is returning values within the range of acos() (it's only defined from -1 to 1).

[Sundar0206]

bang on target........ thanks.. that was the problem ..

but now another problem is i do not know how to avoid it ;)))

Anyways thanks draco