Sasuke,
Nice work, keep it up
Quote: "How do you clip polygons using portals, so if there was an object in front of this terrain, the object would be the portal and any the camera can't see behide the object is clipped. How does this would work?"
If you want a short description of differnt Culling systems I can clear things a bit
Well alot of engines use this as their heart: they use hierachy based systems. What does it mean? Well, Imagine that you have alot of furniture that you've placed inside of your room(s), and you've got alot of rooms in a floor and probably a few/alot of floor in your building and inside your game world!
What should we do to check their visibility? starting from the furnitures? No, the opposite! Why? Here's why:
Many people use Nodes. So the world is the first and highest node in the hierachy. It's called the 'Root' node. In our example it's followed by the building, then floors, then rooms and so on.
Now if the Building's bounding volume is invisible/is not in the scene, then you don't have to check the floors, rooms and others one by one, so we don't render it's child nodes. But if the building is visible then we have to check for visible floors and so on and so forth. This is very fast and efficient. As far as I know DBP already uses frustum and back-face culling which are the very basic of culling techniques. (A node based system should be possible and not that hard to integrate!)
I think what you are talking about is not Portal culling/rendering! what you want is Occlusion Culling, which is based on querying the visible pixels on the screen. Most of the time we use to render the bounding volumes or a low quality version of the scene (lower quality or lower poly objects or both!)... so you have to render the scene once to figure out which objects are visible and which are not; to list the visible objects and prepare them for rendering. I'm not aware of an easy way of doing this in DBP, maybe a plugin or a shader could help taking the advantages of hardware occlusion culling!
Portals are mostly used for indoor scenes. the idea is to check if a portal(like a door) is visible through another and render the rooms based one this method. this one should not be that hard to implement in DBP. but you'll have to write a bunch of code to get to work. there are a few papers/samples on the web.(just google'em)
DBP also supports BSPs (for indoor scenes) but it doesn't seem to be working/that stable!
For terrains you might want to split them up (I think we already have this ability in DBP). so a simple frustum culling should boost things up. (a bit!)
(You might want to look for Octree, etc.)
I prefer a node based scene management + Portals for indoor scenes
(And sorry for my English, I'm not English and I still got to work on it!)
btw, your editor seems like a piece of cake! keep cooking some more
Best regards.
