Hi, vDSP doesn't provide functions to set the coefficients on a double-precision, single-channel biquadratic filter object. You have two options: either convert your double-precision data to single-precision (see vDSP_vdpsp), or use a double-precision, multichannel biquadratic filter object and set the coefficients with vDSP_biquadm_SetCoefficientsDoubleD..

This is because the look-at rotation takes an up vector, and the green cone is up. If your could peek at the ‘next’ rotation, and if dot(new, previous) < 0, then use up: Vector3D(y: -1) instead of +1 (or, really, negate it from whatever was used on the last frame. That would ensure that the object doesn’t flip wildly.