What is the use of the occlusion thingy, I tried to read the docs on it, but I can’t understand its use, so if you could explain its use, and maybe provide an example blend that would be awesome. Thanks.

The way I usually occlude things, is to make a low poly model and a high poly model, and… What the hey! I’ll just make a .blend.


occluder_tut.blend (153 KB)

My understanding of it is that it is:

An object that hides, or occludes another object, not from your view but from the rasterizer. Example. A house with lots of stuff in the interior. In game, from the outside, you can’t see the interior, but the rasterizer can. By placing an occluder object around the house (as I understand it, it can be invisible and not detect collisions), you are essentially cutting the overhead by not asking the rasterizer to deal with everything insie the occluder.

Yes, sounds very useful for games. But…

I’ve never tried it, but from what I’ve read, it is very tricky to use properly, and can backfire and add to your frame rate. I think it’s sort of in it’s infancy…

Correct me if I’m wrong. This is simply my understanding of it.


Not sure what I’m looking at…Kinda stoopid perhaps.

Occluders greatly speed up the framerate if used properly, you need to put them in strategic locations which will occlude tons of polygons when looking from multiple locations rather than just a few polygons and objects.

The more polygons the average occluder blocks from rendering, the better the speed gain and the lower the risk of losing FPS.

So, Inferno, we should do that for the landscape scene, if possible with the map.

Yeah I was planning on using it for something like that, but i wanted to have an idea of how it works before I did anything with it.
@Ace Dragon, Could I just put a large sphere around the main character and have it occlude and make it the child of the character, would that be effective or not, that way it would always occlude objects a sertain distance.

You’d need 6 occluders because the only bounds type they use is a box. (perhaps because it takes less processing time).

You can probably do that, but it’d limit the distance the camera can see before you notice the terrain beyond is empty, you should put occluders inside mountains, large hills, cliffs, ect…, anywhere where they can occlude tons of objects.

Objects that are outside the camera view or are farther away than the camera clip distance will be cut out anyways, so occluders only work on things that are inside the view, and close enough to be seen. Basically, if an occluder comes into view, the framerate drops a certain amount (but if more come into view the framerate shouldn’t drop any more), so you’d better be sure it blocks off enough objects to save you those frames, and more.

As far as I know it doesn’t occlude individual polygons, only entire objects- so if your whole object is behind an occluder except one strand of hair, the whole object will still be rendered. That’s why you really only should use an occluder for, say, the walls of a house, or inside a large mountain that blocks lots of stuff from any angle.

I see, thanks, I think I understand all of this, I’ll try some of it out soon, maybe the mountian thing will work for my scene I am working on. Thanks for your help, If I have any trouble I’ll post them here.

hey just delet the .blend extention and unrar the content.
Open the file and press P to enter on the game mode, and you ll see that everything behind the occluder desapier, that is what the occlusion cooling do.
Good Luck

Nice. 9 fps less when I delete the occluder. Thanks.

Yeah I didn’t notice the frame change without, it is a lot better. Well I guess we’ll have to implement this in our game.

Sorry, play my demo in the game engine, and use the left right arrows to move the box. You need GLSL enabled, and you will see the box and sphere appear and dissappear in realtime. This is what I use to make trees/grass and other complexity.

I see . Very nice. Thank you.