Advanced 3-D Graphics: GNU Maverik—a VR Micro-Kernel

What we have gained is the flexibility to plug together quite different applications within a single VE framework, without compromising performance. That is a gain, but seems to be at the expense of having the application (and application programmer) do all the hard work. However, because Maverik is a framework into which things can be plugged with little performance loss, it is easy to provide commonly useful facilities and objects to get many applications off the ground. For example, Maverik is distributed with libraries of common geometric primitives, cones, cylinders, teapots, an animated avatar, sample graphics file parsers, navigation facilities, 3-D math functions, quarternion codes, stereo, 3-D peripheral drivers for head-mounted display and 3-D mice (see Figure 7) and so forth). If these are useful, then you use them as a good starting point. If they are not, then you provide your own objects and algorithms, perhaps refining the samples provided.

Figure 7. Immersive Editing

This makes it fairly straightforward to get started using the system. In practice, this gives three levels of increasingly sophisticated use.

The real test for Maverik as a research vehicle is how well it allows such pieces to fit into the overall puzzle. The hope is that it will make the task of building VEs “as hard as it should be”, avoiding the feeling that one's efforts are mostly spent “fighting the system”. So far, given a little familiarity with the approach, this looks very promising.

Figure 8. Navigation Algorithms

Recent Maverik developments include a novel force-field navigation algorithm to guide participants around obstacles, and an algorithm for probing geometry ahead of a user to test whether it can be climbed—for example, ladders and steps (see Figure 8). These algorithms integrate into Maverik, but at the time of this writing are released as separate beta sources for testing.

Maverik has no support for audio or video within it. You will need to add your favourite mechanism for those yourself.

Maverik is a single-user VE micro-kernel. It does not include any assistance for running multiple VEs on different machines for sharing a world between people. To do that, you would need to synchronize the VEs yourself across the network. For just navigating around a shared VE, that's not so hard. Running a system with many users across wide area networks with multiple VEs, applications, interaction and behaviour is a more complex challenge. It's a challenge we are working on now with a complementary system that uses Maverik. We aim to release what we have on that under the GNU GPL license later this year.

We are very keen to know how well these ideas work, or don't work, for other people—particularly those with experience of graphics programming. That way, we get to understand more about this whole area. Feedback should be addressed to maverik@aig.cs.man.ac.uk.

Acknowledgements

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