Namkhai Norbu's explanation of cause of Rupakaya

[adinatha]

I didn't follow his explanation how the Rupakaya forms in DC tradition. I got self-perfected state; in rigpa there are no obscurations (only in relative existence); DC is beyond purification and two accumulations, but I didn't follow way Rupakaya forms.

I'm asking if anyone knows what NNR says is cause of Rupakaya or what DC generally says. I've suddenly found my mind cloudy on this topic. I get self-liberation into the kayas during Togal/Yangti. But then Namdrol says that's not enough for manifestation of rupakaya. I thought he said one needs to practice rasayana, chulen, etc.

I'm wondering if that was implicit somewhere in NNR's latest transmission... Thanks.