I remember as a newbie I spent a some time just hanging out at Joan's in Kissling (still there relatively unchanged, although these days it features a somewhat incongruous R2-D2 wandering about). Joan's has a marina feel, with docks, boats, and open air builds. It's bright and touristy. And it never felt empty to me, though I was often the only one there. I attribute this in a large part to the sound of water lapping at the docks, and the ever-circling gulls with their characteristic cries.
Pol at Joan's.
Any veteran of Second Life knows that circling birds are child's play to script, and where to track down a freely available ambient sound script. The point is that basic touches like these, working in harmony with the environment, can make a significant difference in how visitors perceive your build.
People understand this instinctively, which is why you see so many water features across the grid. In addition to being terrific eye candy, they add motion (and often sound) to give a sense of human presence to the world. Many water features, such as fountains, are already partially integrated with their environment simply by being both a scripted and architectural object. Contrast this with the ubiquitous "spinning box" signs, which add superficial motion but are made to grab eyeballs rather than to contribute to environment. Integration is key.
This doesn't mean we always have to go with the expected. For example, Fallingwater Cellardoor of Fallingwater Flowers recently showed me a sample from her new batch of plants. Her prim-based plants have always been equal parts sculpture and organics, and now she's adding some interesting scripted behaviors; her "bug-catcher" flower snatches a buzzing insect out of the air. It's a nice surprise, and I imagine that it would be even cooler if you stumbled across it in somebody's garden.
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