Calculating spotlight falloff on CPU (HDRP)

Hi, how could one calculate spotlight falloff strength at specific distance when using HDRP? I need to calculate this on CPU.

I tried the following:

Code (CSharp):

1. float distanceNormalized = distanceFromSpotLightToSamplePoint / _spotLight.range;
2. float falloff = 1f / (distanceNormalized * distanceNormalized);
3. float intensityAtDistance = _spotLight.intensity * falloff;