virtual world users is likely due to both the lack of penetration of 3D-capable devices into non-niche, non-gaming markets as well as the generally higher pricing of such devices compared to 2-dimensional HIDs. Even those users who do make use of HIDs which provide such features as six degrees of freedom often have to switch between separate 3D and 2D devices in order to navigate their respectively designed interfaces. Like video gamers, some users of virtual world clients may also have a difficult experience with the necessity of proper graphics hardware (such as the more advanced graphics processing units distributed by Nvidia and AMD) for the sake of reducing the frequency of less-than-fluid graphics instances in the navigation of virtual worlds. However, in part for this reason, a growing number of virtual world engines, especially serving children, are entirely browser-based requiring no software down loads or specialized computer hardware. The first virtual world of this kind was Whyville.net, launched in 1999, built by Numedeon inc. which obtained an early patent for its browser-based implementation. Application domains Social Although the social interactions of participants in virtual worlds are often viewed in the context of 3D Games, other forms of interaction are common as well, including forums, blogs, wikis, chatrooms, instant messaging, and video-conferences. Communities are born in places which have their own rules, topics, jokes, and even language. Members of such communities can find like-minded people to interact with, whether this be through a shared passion, the wish to share information, or a desire to meet new people and experience new things. Users may develop personalities within the community adapted to the particular world they are interacting with, which can impact the way they think and act. Internet friendships and participation online communities tend to complement existing friendships and civic participation rather than replacing or diminishing such interactions. Medical Disabled or chronically invalided people of any age can benefit enormously from experiencing the mental and emotional freedom gained by temporarily leaving their disabilities behind and doing, through the medium of their avatars, things as simple and potentially accessible to able, healthy people as walking, running, dancing, sailing, fishing, swimming, surfing, flying, skiing, gardening, exploring and other physical activities which their illnesses or disabilities prevent them from doing in real life. They may also be able to socialize, form friendships and relationships much more easily and avoid the stigma and other obstacles