hierarchical z buffer ?

Obscura

Hey guys, just a question towards rendering guys. I was facing "hzb" for quite long time now, namely in Unreal, and I looked it up and not from the official documentations, but it turns out it stands for "hierarhichal z buffer", and this is a thing used for occlusion culling. From what I understand It will do a pretty good, or excellent job on culling things inside your view, but it will do its pre passes?? And also it is kinda hard to visualize how the render target would look like.  Based on the papers it shows bounds, and also its much lower res than a normal buffer. I think I get the basic idea but there aren't much information available regarding this on the internet, so I thought I could ask here. Also, this just works as it is, unless you change culling mode in Unreal, I would just like to know more about how this works.

Obscura

I know its a kinda hard one 
@radiancef0rge @almighty_gir -  do you maybe know some things about this?
 

Eric Chadwick

Looks like you misspelled hierarchical. Did you try adding prepass to your searches? https://www.google.com/search?source=hp&q=Hierarchical+z+buffer+prepass

Obscura

Possibly.

I have not tried to add pre pass to my searches so far, but from your link I found this paper that I haven't seen before:

http://blog.selfshadow.com/publications/practical-visibility/

Obscura

Alright... After going through this last link, to me it looks like basically you are calculating with screen space taken by certain stuff - example of sky. I could imagine a way of looping things on the cpu (queue-ing them) reading values from your resulting hzb passes, and apply raw / generic culling code - do not render - such as was this at all being on screen , if its possibly inside your frustrum, perform hzb. Which means you basically go down on a chain of resolutions, and if it disappears after some level, it needs to be culled.

Do I understand correctly?