In my game I am trying to create a forest. My problem is that I want all of the trees to have the exact same settings as one “Master Tree” in my level. For example, if I set the LOD distance for the master tree to be 100, all of the other trees would also have their LOD distance set to 100. I tried making all of the trees local duplicates of the master tree, but that only copied mech and material settings, and not LOD information. The only system that I can think of right now is to have empties all over my map spawn a tree in when the game engine starts, but that’s not optimized or efficient, considering that I’m going to put many trees in the level. Is there any way to make many copies of an object that will always change to match one “master” mesh?
group the tree, do add group instance,
tree needs to be on own layer, so it can have it’s origin at 0,0,0
Right, On an empty, (or object) under the yellow cube,(where you name the object) scroll down, click “Group” add the group instance.
To expand a bit on the OPs question.
You still have to have a lot of empties to instance from, right? That means placing a lot of empties which is a PITA. Grass, trees, shrubs, etc. On flat ground you could you just add all them to the group on one empty? But on uneven ground, would could you do?
I suppose you could use an array modifier on the object to be instanced, but i think that would be defeating the purpose, as an array modifier still uses ram. No randomness to it, it’s all in a straight line. Plus it would be difficult to place them on uneven ground.
So, is there a way to instance from a vertex, like dupligroup? (doesn’t work in the game engine)
How would you guys instance a whole group of trees, grass, shrubs on uneven ground?
Using the group instance method that BPR suggested, I was able to create a good solution. I need a big open world, so having thousands or empties was not the way to do this. What I ended up doing was creating several different “mini forests” , ie:
Conifer Dense 01
Shrubs 01
tallGrass01
ect.
i then put these mini forests all over my terrain to add variation. Instead of having thousands of individual trees, I had hundreds of mini-forests. This takes pressure off the CPU and improves performance. I still got the desired result, which was to have all of the sub trees controlled by 1 master tree. When I had to deal with very uneven terrain, I typically just scaled up on the z axis or just rotated the entire mesh.
@ Hellooo
I’m trying to instance a forest with grass and weeds on this hillside. But can’t seem to do it without placing an empty for every group instance. I can do it for flat ground.
But for this hill it’s tedious because of the angles.
http://www.pasteall.org/pic/98017
I’ve seen your blend, but it runs rather poorly on my gaming laptop. Once I add all the animals and AI, it will be worse. But I’ll look at it again to get some ideas.
And it appears that array modifiers that are instanced won’t libload.
I should start my own thread. But first I’ll read Monsters group instancing tutorial.
And do a little more research. I may be doing it wrong.
Thanks Hellooo, and Grenzer for taking the time to answer. 
@ Grenzer Did you make copies of your master tree (Alt D) and add them to your group to make up the mini-forest?