Re: [PATCH] d3dx9: Reduce rounding error in D3DXQuaternionToAxisAngle

[Henri Verbeet]

On 9 November 2017 at 16:45, Alex Henrie  wrote:
> -
>    *pangle = 2.0f * acosf(pq->w);
> -
>    *pangle = 2.0f * acos(pq->w); /* acosf has too much rounding error */

Does that rounding error by any chance get better if you replace
"acosf(x)" with "atan2f(sqrtf((1.0f - x) * (1.0f + x)), x)"?