Culling Performance

[L B]

There have been many discussions about culling performance. Notably:

• http://www.leadwerks.com/werkspace/topic/4449-showhide-heavy-trees/
  
• http://www.leadwerks.com/werkspace/topic/3995-entity-cull-time-optimization/
  
• http://www.leadwerks.com/werkspace/topic/3956-model-setviewrange-causes-crash/
  

Josh often says that he needs a scene file to test. Here is one, along with the 3D model "filler.gmf" used in it.

• http://localhostr.com/file/rg5ZGkP/Culling.sbx
  
• http://localhostr.com/file/xT1HJD0/Filler.gmf
  
• http://localhostr.com/file/QIcDJF8/FillerLOD1.gmf
  

Here is a screenshot of the performance assessment:

 

I want to stress the following points:

• The polygon count is 25k, which is nothing for Leadwerks. Draw time is 1ms.
  
• The world time is of 7ms, 5 of which are taken by entity cull time. This is enormous. I often get 6 or even 7ms taken by the cull time, out of the total 7ms.
  
• There seems to be 2376 entities drawn, whereas the square is 24x24=576 cubes. The other entities are the directional light. Perhaps the LOD counts as 2, but even then, it's not 2376.
  

If you don't see performance drops yet, try multiplying that grid 4, 8, or 16 times. Then you'll notice cull time starts to rise in the 30-60ms.

 

Another interesting point is that when you look down from the basic camera view, there seems to be a massive glitch in culling. Although no entities are in view (screenshot shows some only to indicate how I lowered the view, but you can lower further to show none), almost all the entities and polygons are still drawn. Also note that culling still takes the most of the render time. This seems to indicate frustrum culling is not only slow but bugged.

 

This needs to be fixed, as it causes massive drops in performance for apparently no reason. Or, there needs to be a way for us to disable culling in that case. I'm interested in learning how.

[Josh]

It's working as I would expect.

 

The world time is of 7ms, 5 of which are taken by entity cull time. This is enormous. I often get 6 or even 7ms taken by the cull time, out of the total 7ms.

Culling has a cost, but typically also results in savings because entities get skipped. If all entities are onscreen, there will be no savings to balance this cost.

 

Another interesting point is that when you look down from the basic camera view, there seems to be a massive glitch in culling. Although no entities are in view (screenshot shows some only to indicate how I lowered the view, but you can lower further to show none), almost all the entities and polygons are still drawn. Also note that culling still takes the most of the render time. This seems to indicate frustrum culling is not only slow but bugged.

It's drawing a lot of meshes for the shadow render. The directional light shadow does not just render what you see, it renders anything the directional light sees that might cast a shadow into your field of view. An object can be offscreen, but still cast a shadow that falls onscreen. The directional light shadow renders three passes for the different light volumes the shadow uses.

 

If you disable shadows you will see that the number of entities drawn corresponds perfectly to what you see onscreen.

[L B]

I see, thanks for the reply.

 

Can I somehow disable culling or improve its performance though?

[Josh]

In normal usage culling will result in a massive improvement to otherwise unplayable framerates. If you pack thousands of entities into a small space, of course performance will be bad.

 

It's fine for polygon counts to be high, but you should keep the number of passes / meshes as low as possible. This is the nature of modern graphics hardware.

[L B]

Can I somehow disable culling or improve this specific case then?

[LordHippo]

Can I somehow disable culling or improve this specific case then?

 

I think Josh already answered it:

 

It's fine for polygon counts to be high, but you should keep the number of passes / meshes as low as possible. This is the nature of modern graphics hardware.

 

BTW, is this high number of objects your requirement?

[Marleys Ghost]

Just some extra info for you from your test map and objects with all FX on and settings at max.

 

 

[YouGroove]

@Marleys Ghost :

Why in your case it's ok compared to Lazlo ?

What you have done differently ? the materials of objects ?

[Marleys Ghost]

Same scene, same model, nothing changed the pics were for additional info.

[L B]

Same scene, same model, nothing changed the pics were for additional info.

Not to mention your killer GPU, vs my puny 9600 GT.

[LordHippo]

Not to mention your killer GPU, vs my puny 9600 GT.

 

But the culling time should be dependent on the GPU, as far as occlusion culling is not used.

[Josh]

But the culling time should be dependent on the GPU, as far as occlusion culling is not used.

You mean CPU, right?

[LordHippo]

You mean CPU, right?

 

Yeah.

I meant "should NOT be dependent on the GPU".

[L B]

Oh, right.

Well in that case, let me rectify my statement: Your killer CPU versus my puny 2.3 GHz Dual-Core.

[Marleys Ghost]

Oh, right.

Well in that case, let me rectify my statement: Your killer CPU versus my puny 2.3 GHz Dual-Core.

 

 

More than likely, as I said Just some extra info for you from your test map and objects.

[Scott Richmond]

Can I somehow disable culling or improve this specific case then?

Yes, you can:

Framework fw(CREATENOW);
fw.main.world.SetCullRange(20.0F, 250.0F, 500.0F); // Near, Medium and Far view ranges


for(int x = 0; x < 100; x++) {
 for(int y = 0; y < 100; y++) {
for(int z = 0; z < 1; z++) {
  Model *model = new Model();
  model->Load("abstract::oildrum.gmf");
  model->SetViewRange(VIEWRANGE_NEAR, RECURSIVE);
  model->Move(x, y, z);
}
 }
}

That'll spawn 10,000 oildrums and only render ones 20 meters around the camera. Seems to work fairly well for me.