Second Life Forums Archive

Tod69 Talamasca

The Human Tripod ;)

Join date: 20 Sep 2005

Posts: 4,107

03-31-2006 23:59

Was just wondering if anyone knew this: Does SL do zoning like in other builders such as the Unreal Tournament Editor? As in, if I have a large building in front of me, is it rendering whats on the other side even though I can't see it?

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Static Sprocket

Registered User

Join date: 10 Feb 2006

Posts: 157

04-01-2006 00:42

Second Life does not do object culling (as far as I can tell), so as long as an object is within your draw distance and viewing angle it is being rendered. This is one of the reasons for SL's generally bad rendering (fps) on older cards.

Osgeld Barmy

Registered User

Join date: 22 Mar 2005

Posts: 3,336

04-01-2006 00:47

good question, i think so

not rendering stuff that the camera cannot see is such an old feature i dont ever think about it anymore (i had a bitmap 3d engine simmilar to wolfenstien back in the early 90's that had it hehe)

i know with the LOD and culling that things past or on the edge of your draw distance wont, but im not shure if the other side of a wall is being rendered at that moment if you cant see it

Chosen Few

Alpha Channel Slave

Join date: 16 Jan 2004

Posts: 7,496

04-01-2006 06:11

Yes and no. What you're asking about is called "culling" in graphics lingo, by the way. I'm not sure why the Unreal editor might refer to it as "zoning". That's odd.

Anyway, back to the yes and no. The yes is that SL does backface culling, meaning it only renders one side of each polygon, the front. This is easy enough to notice. Just put a transparent texture on one side of a box, and you'll be able to see all the way through the prim. You won't see the inside surfaces of the box.

The no is SL does not do occlusion culling, which I think is more what you were asking about. All objects are drawn, whether other objects are in front of them or not. If you've got a big building in front of you with a tree behind it, the tree will be rendered even though you can't see it. The building just gets rendered right on top of it. I'm not sure the technical reason why they do it this way, but whatever it is, it better be a good one since it slows things down considerably.

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AJ DaSilva

woz ere

Join date: 15 Jun 2005

Posts: 1,993

04-01-2006 07:39

I've not used it, but I think the Unreal editor calles it "zoning" because it operates by dividing a level (manually I believe) into areas/zones (e.g. separate rooms) to make it easier for the rendering engine to know what it needs to render.

Tod69 Talamasca

The Human Tripod ;)

Join date: 20 Sep 2005

Posts: 4,107

04-01-2006 08:31

From: AJ DaSilva

I've not used it, but I think the Unreal editor calles it "zoning" because it operates by dividing a level (manually I believe) into areas/zones (e.g. separate rooms) to make it easier for the rendering engine to know what it needs to render.

You Got It!

couldnt think of the general term used in graphics so I used UED's terminology

_____________________

really pissy & mean right now and NOT happy with Life.

Warda Kawabata

Amityville Horror

Join date: 4 Nov 2005

Posts: 1,300

04-01-2006 08:47

From: Chosen Few

Yes and no. What you're asking about is called "culling" in graphics lingo, by the way. I'm not sure why the Unreal editor might refer to it as "zoning". That's odd.

Anyway, back to the yes and no. The yes is that SL does backface culling, meaning it only renders one side of each polygon, the front. This is easy enough to notice. Just put a transparent texture on one side of a box, and you'll be able to see all the way through the prim. You won't see the inside surfaces of the box.

The no is SL does not do occlusion culling, which I think is more what you were asking about. All objects are drawn, whether other objects are in front of them or not. If you've got a big building in front of you with a tree behind it, the tree will be rendered even though you can't see it. The building just gets rendered right on top of it. I'm not sure the technical reason why they do it this way, but whatever it is, it better be a good one since it slows things down considerably.

About occlusion culling. This is uincredibly complicated to accomplish well, as first to need to establish whether the nearer object completely bloks teh view, then whether wind could cause either object to move out of teh line of sight to make teh far object visible, then consider whether thee are any transparency issues. Even for a graphical engine as primitive as that used in the Bard's Tale (a 25-odd year old RPG), this is no trivial task. The cycles to calculate the line of sight would be better spent just drawing the thing anyway. It takes almost as many cycles.

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Zoning?

Zoning?
Tod69 Talamasca The Human Tripod ;) Join date: 20 Sep 2005 Posts: 4,107	03-31-2006 23:59 Was just wondering if anyone knew this: Does SL do zoning like in other builders such as the Unreal Tournament Editor? As in, if I have a large building in front of me, is it rendering whats on the other side even though I can't see it? _____________________ really pissy & mean right now and NOT happy with Life.
Static Sprocket Registered User Join date: 10 Feb 2006 Posts: 157	04-01-2006 00:42 Second Life does not do object culling (as far as I can tell), so as long as an object is within your draw distance and viewing angle it is being rendered. This is one of the reasons for SL's generally bad rendering (fps) on older cards.
Osgeld Barmy Registered User Join date: 22 Mar 2005 Posts: 3,336	04-01-2006 00:47 good question, i think so not rendering stuff that the camera cannot see is such an old feature i dont ever think about it anymore (i had a bitmap 3d engine simmilar to wolfenstien back in the early 90's that had it hehe) i know with the LOD and culling that things past or on the edge of your draw distance wont, but im not shure if the other side of a wall is being rendered at that moment if you cant see it
Chosen Few Alpha Channel Slave Join date: 16 Jan 2004 Posts: 7,496	04-01-2006 06:11 Yes and no. What you're asking about is called "culling" in graphics lingo, by the way. I'm not sure why the Unreal editor might refer to it as "zoning". That's odd. Anyway, back to the yes and no. The yes is that SL does backface culling, meaning it only renders one side of each polygon, the front. This is easy enough to notice. Just put a transparent texture on one side of a box, and you'll be able to see all the way through the prim. You won't see the inside surfaces of the box. The no is SL does not do occlusion culling, which I think is more what you were asking about. All objects are drawn, whether other objects are in front of them or not. If you've got a big building in front of you with a tree behind it, the tree will be rendered even though you can't see it. The building just gets rendered right on top of it. I'm not sure the technical reason why they do it this way, but whatever it is, it better be a good one since it slows things down considerably. _____________________ . Land now available for rent in Indigo. Low rates. Quiet, low-lag mainland sim with good neighbors. IM me in-world if you're interested.
AJ DaSilva woz ere Join date: 15 Jun 2005 Posts: 1,993	04-01-2006 07:39 I've not used it, but I think the Unreal editor calles it "zoning" because it operates by dividing a level (manually I believe) into areas/zones (e.g. separate rooms) to make it easier for the rendering engine to know what it needs to render.
Tod69 Talamasca The Human Tripod ;) Join date: 20 Sep 2005 Posts: 4,107	04-01-2006 08:31 From: AJ DaSilva I've not used it, but I think the Unreal editor calles it "zoning" because it operates by dividing a level (manually I believe) into areas/zones (e.g. separate rooms) to make it easier for the rendering engine to know what it needs to render. You Got It! couldnt think of the general term used in graphics so I used UED's terminology _____________________ really pissy & mean right now and NOT happy with Life.
Warda Kawabata Amityville Horror Join date: 4 Nov 2005 Posts: 1,300	04-01-2006 08:47 From: Chosen Few Yes and no. What you're asking about is called "culling" in graphics lingo, by the way. I'm not sure why the Unreal editor might refer to it as "zoning". That's odd. Anyway, back to the yes and no. The yes is that SL does backface culling, meaning it only renders one side of each polygon, the front. This is easy enough to notice. Just put a transparent texture on one side of a box, and you'll be able to see all the way through the prim. You won't see the inside surfaces of the box. The no is SL does not do occlusion culling, which I think is more what you were asking about. All objects are drawn, whether other objects are in front of them or not. If you've got a big building in front of you with a tree behind it, the tree will be rendered even though you can't see it. The building just gets rendered right on top of it. I'm not sure the technical reason why they do it this way, but whatever it is, it better be a good one since it slows things down considerably. About occlusion culling. This is uincredibly complicated to accomplish well, as first to need to establish whether the nearer object completely bloks teh view, then whether wind could cause either object to move out of teh line of sight to make teh far object visible, then consider whether thee are any transparency issues. Even for a graphical engine as primitive as that used in the Bard's Tale (a 25-odd year old RPG), this is no trivial task. The cycles to calculate the line of sight would be better spent just drawing the thing anyway. It takes almost as many cycles.