[opensource-dev] Interested in Terrain Advancement

Dzonatas Sol dzonatas at gmail.com
Fri Apr 23 13:26:10 PDT 2010

There does seem to be a collective feel that the terrain needs to 
upgraded somehow. Even a Linden suggested maybe a way to override it if 
the builder choses, like with sim sized mega prims.

My first concern is LOD. The constant changes of LOD on the terrain make 
the appearance the terrain unnatural and unstable. There are times where 
we spend lots of time to get the terrain to look just perfectly aligned 
with other objects nearby. When one decides to walk away 20m, 40m, 60m, 
however, the perfect alignment becomes a prefect fashion statement for a 
drunk bulldozer. The hard work undertaken to detail the alignment of the 
terrain seems like a complete loss.

As I've used other renders, lets pick on Call of Duty, the terrain is 
pretty stable even at a distance. It has to be. The mere jump of LOD in 
the terrain could mean a way to cheat in Deathmatch sniper rounds. You 
know how snipers love to crawl around the terrain. That kind of 
stableness doesn't happen when the drunk bulldozer decides to 
rearrangement the landscape every frame you move. Call of Duty uses the 
Source Engine, yet this isn't a 'lets all switch over to the Source 
Engine' rant. It is a use-case that shows that even on old steampunk 
video cards there still have the coal to burn up the pixels and display 
a stable landscape. The use-case means, bottomline, it is possible.

Maybe a baby-step solution is just to have an option to turn-off the LOD 
for the current sim, and maybe nearby sims. The problem here, maybe, is 
that the changes to add vertex limits would be affected by this. It 
might not be all that simple like it was in the past without the vertex 
limits. Therefore, there would need to be separate vertex limits: one 
for the terrain and the rest for objects.

Here is another use-case with a collada file: Lets say I have a collada 
file that contains a very detailed structure of a volcano (terrain 
only).  The volcano is 1km wide. That crosses several 256m sims. There 
are lava tunnels that lead inside.

The suggested solution was to use a sim sized mega-prim. To do that with 
scuplties would be hard for more than just looks. Sculpties need to 
calculate all the phsyics, yet the collada file could have that already 
detailed and compiled with the file.

How do we do this with the stock viewer even if we used sculpties? The 
stock viewer doesn't include a "sit on this object here like one sits on 
land now anywhere" option. If we used a mega-prim, it would disabled the 
ability to sit anywhere on the terrain.

The other idea is to import a terrain, which is an available feature. 
That doesn't allow us to have multiple height maps, like lava tubes. If 
a lava tube crossed a sim to another, there would be a hole in the 
terrain in one sim. There current terrain engine doesn't allow holes. 
Multiple height maps would allow us to have holes in the terrain. The 
physics detail of a scupltie bent to make that hole doesn't preform (and 
I don't mean just frame optimization.. I mean like how a skirt clearly 
either looks good or not when you sit down kind of 'preform'.)

So, maybe the solution include that baby step.. to allow multiple height 
map layers. A Lava tube could be done with three layers. One for the 
bottom of the tunnel. One for the top. And one for the side of the 
volcano above the tunnel. There would be needed an extra feature with 
the height map to allow empty spaces, to allow where the tunnel opens 
into the side of the volcano.

So, before we even digress into the advantages of collada refineries, it 
seems the first two baby steps would be to fix LOD and allow an 
arbitrary number of terrain layers.

I would like to see what others think about this.

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