Estimation of the transmittance becomes a mix of approaches from AMAPVox 1.3.2 and 1.3.5, i.e. we set a maximum number of ray records (user defined) up to which AMAPVox stores every ray records for an accurate transmittance estimation at the end of the voxelisation. If the number of ray records exceeds the max for a given voxel during the voxelisation, then AMAPVox switches to fallback mode and proceeds with estimation of the transmittance with fixed set of transmittance values. Default mode is accurate, relatively fast but heavy on memory whereas fallmode is less accurate, lighter on memory but computation expensive.