Octree question

ikslm · Post by **ikslm** » Mon Nov 10, 2008 12:03 pm

Hey all.

I have a scene (level) where i create ~~7000 unique ISceneNodes each with its own custom geometry (auto generated, not loaded from a file). At any moment i can remove/modify any of them.

So every frame, the engine has to check every node if it is in the frustum? That makes a lot of checking...?

Is there a way to throw all this nodes into octree? (nodes are "static" they don't change position and the bbox is constant). I've been looking at the addOctTreeSceneNode and it only receives the Mesh param, not the ISceneNodes...

aanderse · Post by **aanderse** » Mon Nov 10, 2008 2:56 pm

No such class exists in irrlicht. Ogre has that type of octree, but no dice for irrlicht.

You could make one though

You wouldn't even have to do it from scratch. I saw someone had made a Quadtree Scene Node for irrlicht. If you didn't need fully 3 dimensional you could use the Quadtree scene node, but if you needed to cull based on all 3 dimensions you would have to modify it to make it an octree.

http://br.geocities.com/paulo_cmv/

ikslm · Post by **ikslm** » Mon Nov 10, 2008 4:08 pm

Yes, in my case the quadtree would be better. I guess i'll have to make it myself. But i guess something like that would be a nice addition to the engine.

JP · Post by JP » Mon Nov 10, 2008 4:16 pm

It would be much better if all your objects were in one scene node and you rendered them all at once rather than individually. If you're removing them at any time then that might not make that easy or even possible though...

ikslm · Post by **ikslm** » Mon Nov 10, 2008 4:21 pm

.... and usually only 10% are visible per frame. so, quadtree

or i could make a BIG (1 or more, since we have the 65xxx buffer size limit) vertex and index list, and then erase/add/modify vertices/indices when needed.

rogerborg · Post by **rogerborg** » Mon Nov 10, 2008 4:42 pm

ikslm wrote:Yes, in my case the quadtree would be better. I guess i'll have to make it myself. But i guess something like that would be a nice addition to the engine.

It's do-able, but non-trivial. We'd have to deal with shifting objects around the oct-tree as they move / rotate / scale, as well as taking into account the descendants of the oct tree's scene node children (including when nodes get reparented), so it's not a lunchtime job.

That said, patches are always very welcome, particularly if they come with test apps. I'm still working through the bug backlog, but do intend to get around to the feature requests after 1.5 is cut.

ikslm · Post by **ikslm** » Mon Nov 10, 2008 5:24 pm

Well for my scenario the things are simpler:

1. i would use quadtree
2. i'd use quadtree only for static objects (by static i mean that they have constant position and bbox), so this quadtree would receive a vector of nodes it should contain and some quadtree params
3. for other objects (animated, movable... in my case there are ~~ 100 of them) i'd use normal frustum culling

ikslm · Post by **ikslm** » Tue Nov 11, 2008 1:26 pm

Anyway, i'm woking on the quadtree for my purpose. I'll report the speed increase when i finish.

ikslm · Post by **ikslm** » Wed Nov 12, 2008 11:47 am

simple question.

how can i do a "bounding box in current view frustum" test?

rogerborg · Post by **rogerborg** » Wed Nov 12, 2008 1:00 pm

Swipe the culling code from source/Irrlicht/CSceneManager::isCulled().

ikslm · Post by **ikslm** » Thu Nov 13, 2008 11:18 am

Ok, done. I'm happy with the result. I got a 4x-6x boost of FPS. Gone from 60FPS to 400FPS. Thanks for the help.

blizuke · Post by **blizuke** » Sun Jul 18, 2010 9:57 am

Has anyone implemented anything like this, that they have already shared or are willing to share, please?

It would be very helpful.

Irrlicht Engine

Octree question

Octree question

Anyone have code like this to share?