Occlusion Culling...
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Gigs Taggart
The Invisible Hand
Join date: 12 Feb 2006
Posts: 406
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04-13-2006 21:51
When I saw occlusion culling on the list I nearly peed myself.
I thought it would bring real privacy and security to secondlife, especially if it were made mandatory. No more looking through walls by panning the camera around, no more sithacking through walls.
Logged into preview, and it doesn't seem to do anything of the sort. In fact it doesn't even seem to raise FPS all that much even in a simple 10X10X10 hollowed cube box with ends on it.
FPS are terrible BTW, I was getting between 3 and 20. Occlusion culling in the simple closed prim room seems to make about a 5-10 FPS improvement.
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Feynt Mistral
Registered User
Join date: 24 Sep 2005
Posts: 551
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04-14-2006 05:33
I've noticed this too. Occlusion culling is not... culling. It seems to me it's not nearly agressive enough in what it considers blocked from view, the ground especially. Actually it was my special dream that OC would remove all the unnecessary polygons from the ground I usually don't see and speed up rendering by only showing me the parts of the ground that my camera's eye can glean. I know the kind of speed difference being 300m in the air and above makes (where the ground is no longer rendered), and even with 8000 prims at and above that altitude I didn't lag all that much.
So please, try tweaking the agressiveness of the culling. Or better still, put in an option in the preferences for the user to decide what's too agressive and what isn't. I wouldn't mind not catching an odd prim barely poking out behind a wall, or seeing the abyss below the groundever so slightly as I creep towards a window to peer down.
Addendum: After a conversation with Eep in world I was commended for my correctness in the "agressiveness" factor, but told that I had no idea what I was talking about when asking for improvements. That may be so, but at least we can agree that better culling needs to take place. With Octree displaying in the client I notice very few, if any, culling blocks (red blocks). Even with a 10x10 wall in front of my camera I don't cull things just on the other side and plainly out of view. Any closer to the wall and I'd be clipping the prim (and thus seeing what was on the other side anyways).
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Alondria LeFay
Registered User
Join date: 2 May 2003
Posts: 725
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04-14-2006 11:41
I have found the Occlusion Culling may have actually DRAMATICALLY decreased my fps, although the situation of where I am may be significantly different than most. Again, this is a hunch, but my tower in Miramare is next to an extremely high density build (the building has a couple thousand prims). When looking in the general direction of the building, my computer basically locks up for a few seconds per movement I make - I am suspecting it is calculating what should be visible, which locks the screen.
Incidently, anyone have success with the ctrl-shift-o to turn this feature off? It does not appear to do anything for me (or at least not anything apparent like a message or a change in fps).
/Edit-Update - Looking through the debug messages, I am seeing thinks like "WARNING: OCTREE IS HUGE: 32321". Without a doubt, calculating whether 32321 prims should be viewable or not would have negative effect on CPU load, which would explain my couple second freeze when I look at the sim. Further, the ctrl-shift-o does seem to active/deactive the culling, however I suspect it is still calculating the octree, or something. Regardless, increasing FPS doesn't help if the computer locks a few seconds per frame on CPU calculations
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Hello Toonie
Registered User
Join date: 25 Jul 2005
Posts: 212
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04-14-2006 12:10
Agree on the aggressiveness thing. When it works, it works (though not a radical improvement, just a few tens-of-percent framerate increase tops, but I'm sure not complaining at that), but it kicks in a whole lot less than one might expect.
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Feynt Mistral
Registered User
Join date: 24 Sep 2005
Posts: 551
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04-14-2006 15:00
I also haven't seen this whole "if you can't see the outside, you'll render much faster" routine happen yet. I jumped into a house on someone's property and stared into the back corner with no windows in sight, yet my frame rate didn't change and I saw no red blocks appearing outside (when indeed there should have been many).
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Chosen Few
Alpha Channel Slave
Join date: 16 Jan 2004
Posts: 7,496
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04-14-2006 15:01
From: Gigs Taggart When I saw occlusion culling on the list I nearly peed myself.
I thought it would bring real privacy and security to secondlife, especially if it were made mandatory. No more looking through walls by panning the camera around, no more sithacking through walls.
Logged into preview, and it doesn't seem to do anything of the sort. In fact it doesn't even seem to raise FPS all that much even in a simple 10X10X10 hollowed cube box with ends on it.
FPS are terrible BTW, I was getting between 3 and 20. Occlusion culling in the simple closed prim room seems to make about a 5-10 FPS improvement. I think you misunderstood the point, Gigs. I guess I can see how it might have sounded that way from the description, but occlusion culling was never meant to have anything to do with privacy in any way, shape, or form. It's a performance enhancement, plain and simple. Occlusion culling is a very important part of 3D rendering, and graphics processing. Its previous absense in SL was something that I and a lot of other graphics industry types had been complaining about for years. Again, it's not something that was ever meant to have social implications like privacy or anything along those lines. It's just a technical improvement to the software. It's a smarter, less computationally expensive way to render the world. To explain what occlusion culling actually does, here's a real world analogy. Think of it as if you were painting picture of a wrapped christmas present. Let's say the present itself is a bag of marbles in a nice gift box, wrapped with shiny paper. Were you to paint the picture without occlusion culling, you'd first paint all the individual marbles, then you'd cover them up by painting the bag around them, then you'd cover the bag with the box, and finally you'd cover the box with the paper. Needless to say, all those objects would take you an awfully long time to paint, and most of your efforts would have been pointless because you would have painted a hundred items you'll never see. It makes a lot more sense just to paint the wrapped box, and forget all about the contents (cull them), since they're not going to be seen in the picture (they're all occluded by the wrapping paper). The way SL works currently (without occlusion culling) is it paints everything, without regard to what you can actually see or what you can't. Put a thousand marbles in a closed box, and SL will render the whole thousand, plus the box, even though you all you can actually see is the box. Under the new rendering system (wth occlusion culling) however, the only thing that will get rendered is the box. The rendering engine won't have to worry about any of themarbles, since they're all occluded from view. As a result, your FPS will improve, as you've already experienced. If I'm reading right, you say you're getting 3-20 FPS with occlusion culling off, and then an additional 5-10 with it on. Well, that's an increase of somewhere between 15% and 267%! That's huge! Okay, I can inderstand going from 3 to 8 might not feel like much of an accomplishment, but it is. That's almost tripling your frame rate.
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Feynt Mistral
Registered User
Join date: 24 Sep 2005
Posts: 551
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04-14-2006 15:11
From: Chosen Few Under the new rendering system (wth occlusion culling) however, the only thing that will get rendered is the box. The rendering engine won't have to worry about any of themarbles, since they're all occluded from view. As a result, your FPS will improve, as you've already experienced. If I'm reading right, you say you're getting 3-20 FPS with occlusion culling off, and then an additional 5-10 with it on. Well, that's an increase of somewhere between 15% and 267%! That's huge!
Okay, I can inderstand going from 3 to 8 might not feel like much of an accomplishment, but it is. That's almost tripling your frame rate.
Except for me it doesn't seem to cull nearly enough. >/ I do notice a 2 fps increase overall, bringing my base stutter to 4 fps now, but it's not as agressive as I'd hoped it would be. However you're right though, if I got 8 fps as a base I'd be ecstatic.
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Ron Overdrive
Registered User
Join date: 10 Jul 2005
Posts: 1,002
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04-14-2006 16:36
From: Feynt Mistral Except for me it doesn't seem to cull nearly enough. >/
I do notice a 2 fps increase overall, bringing my base stutter to 4 fps now, but it's not as agressive as I'd hoped it would be. However you're right though, if I got 8 fps as a base I'd be ecstatic. Yeah I'm the same way Feynt, no difference what so ever even when I do finally see those red blocks. I'm actually very dissapointed by the weakness of this new culling, especially when avitars are uneffected by it wich should have been a priority.
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Feynt Mistral
Registered User
Join date: 24 Sep 2005
Posts: 551
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04-14-2006 16:49
Priority number 1 in fact. Why would I want to see a 200 prim wig of floppy hair when it's behind a wall?
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