Occlusion culling is really tough in systems where users can add content to the world. Especially if there's translucency. As with windows (not Windows), or layered clothing.
You're in a room without windows. Everything outside the room is culled. Frame rate is very high. Then you open the door and go outside into a large city. Some buildings have big windows showing the interior, so you can't cull the building interior. You're on a long street and can look off into the distance. Now keep the frame rate from dropping while not losing distant objects.
Games with fixed objects can design the world to avoid these situations. Few games have many windows you can look into. Long sightlines are often avoided in level design. If you don't have those options, you have to accept that distant objects will be displayed, and level of detail handling becomes more important than occlusion. Impostors. Lots of impostors.
Occlusion culling itself has a compute cost. I've seen the cost of culling big scenes exceed the cost of drawing the culled content.
This is one of those hard problems metaverses have, and which, despite the amount of money thrown at the problem, were not solved during the metaverse boom. Meta does not seem to have contributed much to graphics technology.
This is much of why Second Life is slow.
danielvaughn 56 minutes ago [-]
I was thinking about this problem a few days ago, imagining a semi-online game where players could create a collective city by plotting buildings. The "grid" would be some kind of pre-determined voronoi pattern, in theory making occlusion culling easier.
greggman65 56 minutes ago [-]
> Quake made PVS famous. It’s still useful in some indoor games where the scene geometry is static and bake time is acceptable.
It was used extensively in outdoor games like Jak and Daxter.
nickandbro 5 hours ago [-]
Love this, I will now use backface culling for my game:
Backface culling has been common since the late 1990s when we started using face normals to determine lighting rather than per-vertex lighting. Pretty much every 3D game engine since about 2004 has included and enabled it by default. How is it that you made a game that doesn't use it?
01HNNWZ0MV43FF 31 minutes ago [-]
For the curious readers, backface culling (at least in the way fixed-function OpenGL does it, and probably newer APIs still do) is not based on face normals, it's based on winding order of triangles, so it works even if normals are not used.
Also face normals (flat shading) are generally considered older tech than per-vertex lighting (Gouraud shading). Newer stuff since 2008-ish is generally per-pixel using normal maps for detail.
nickandbro 4 hours ago [-]
I didn't use a game engine
Tanoc 3 hours ago [-]
Ahhh. So you used a wrapper or a library? Interesting then. I had assumed that almost every rendering method enables frustrum, occlusion, and backface culling by default if only to clear the number of objects needed to be tracked in memory. One thing I noticed in your game is that it's based on the absolute mouse position, which with a 16:9 window makes it difficult to turn in certain situations because your horizontal movement space is much larger than the vertical movement space and that adversely affects turning speed. Changing so that is based just on horizontal mouse movement or adding keyboard controls might be better.
nickandbro 3 hours ago [-]
Thanks for the feedback, I’ll try to get that sorted out.
LarsDu88 6 hours ago [-]
PVS isn't that expensive to compute. Especially nowadays. I assume this is actually referring to the binary space partitioning techniques used in DOOM and improved in Quake, Half-Life, etc in the late 90s, early 2000s.
The BSP tree was also extremely useful for optimizing netcode for games like Quake 3 Arena and games within that family and time period I believe.
yards 5 hours ago [-]
I always wonder about this IRL...I'm at work rn, is my apartment still rendered?
You're in a room without windows. Everything outside the room is culled. Frame rate is very high. Then you open the door and go outside into a large city. Some buildings have big windows showing the interior, so you can't cull the building interior. You're on a long street and can look off into the distance. Now keep the frame rate from dropping while not losing distant objects.
Games with fixed objects can design the world to avoid these situations. Few games have many windows you can look into. Long sightlines are often avoided in level design. If you don't have those options, you have to accept that distant objects will be displayed, and level of detail handling becomes more important than occlusion. Impostors. Lots of impostors.
Occlusion culling itself has a compute cost. I've seen the cost of culling big scenes exceed the cost of drawing the culled content.
This is one of those hard problems metaverses have, and which, despite the amount of money thrown at the problem, were not solved during the metaverse boom. Meta does not seem to have contributed much to graphics technology.
This is much of why Second Life is slow.
It was used extensively in outdoor games like Jak and Daxter.
https://slitherworld.com
Also face normals (flat shading) are generally considered older tech than per-vertex lighting (Gouraud shading). Newer stuff since 2008-ish is generally per-pixel using normal maps for detail.
The BSP tree was also extremely useful for optimizing netcode for games like Quake 3 Arena and games within that family and time period I believe.
https://twilightzone.fandom.com/wiki/A_Matter_of_Minutes
[1] https://en.wikipedia.org/wiki/If_a_tree_falls_in_a_forest_an...