btSqrt Approximation Problem

[sio2interactive]

The following code on btSqrt in btScalar.h when using approximation doesn't work on MacOS (well partially work), sometimes I get NAN as the result of the function:

Code: Select all

    double x, z, tempf;
    unsigned long *tfptr = ((unsigned long *)&tempf) + 1;

	tempf = y;
	*tfptr = (0xbfcdd90a - *tfptr)>>1; 
	x =  tempf;
	z =  y*btScalar(0.5);                    
	x = (btScalar(1.5)*x)-(x*x)*(x*z);        
	x = (btScalar(1.5)*x)-(x*x)*(x*z);
	x = (btScalar(1.5)*x)-(x*x)*(x*z);
	x = (btScalar(1.5)*x)-(x*x)*(x*z);
	x = (btScalar(1.5)*x)-(x*x)*(x*z);
	return x*y;

Is there a way to fix this?

[Erwin Coumans]

This code is never enabled, is it? Who defines USE_APPROXIMATION?

We better just remove it, and just use sqrtf.
Thanks,
Erwin