Opeth drum pedals?

I believe that indeed on atleast Deliverance triggers were used for the heavy doublebass sections. As for the pedals, I'm guessing Iron Cobra's, I think it's been asked before but I'm not sure about this.
 
trigger used to have a constant level of bass drum or everything
trigger detect a hit and the sampler produce a bass drum sample

trigger allow to have a constant level

(i hope you understand me)
 
Triggers on a bass drum are simple. You hit the bass pedal, and the trigger will detect the hit and send it to a "brain" or a trigger module which then plays a sample of a bass drum over the PA. That's a very basic explanation of a bass drum trigger.

From what I remember, Deliverance at least was recorded with acoustic drums, and then when it was mixed, Andy Sneap mixed it so it's 50% acoustic drums and 50% samples coming through for a thicker sound.
 
trigger might not be used during recording session, but a VST existing which work as a trigger but there is a threshold: if the level of bass drum hit is higher than threshold a sample is playing

i guess Melodyne and celemony do this