From: Jayson Raymond Subject: Re: sci.virtual-worlds Date: Tue, 9 Jul 91 14:12:48 PDT Regarding (C)IG's, richard@.ist.ucf.edu (Richard Dunn-Roberts) writes: >Jayson is correct that IGs have a lot of benefits for use in VR. However, >highly interactive simulations such as VR still present some inherently >difficult problems that IGs cannot handle in current incarnations. Some of >the problems of using IG's include: > > - limited polygon budget. Most high-end systems are capable of > providing on the order of 5K-6K textured polygons at 60Hz frame > rate. Cost for these systems is on the order of $1M per channel. > For lower end systems, polygon budgets of 1K-2K at 30Hz or less > is common, and it is real easy to exceed this budget with a world > of any complexity. The current technology push for programs such as CCTT and others should go along way to increase polygonal performance at a decreased cost. And this is still better then most workstations, at least when considering textured poly's (I'd trade a fewer number of polygons for more texturing ability any day of the week, because the apparent scene complexity provided by well done textures is phenomenal). > > - Dynamic models on IGs are very limited. For example, BBN's SIMNET > has moving tanks and aircraft that can interact. However, the terrain > database is static. This is actually a much larger part of the > database than the moving models. This helps reduce correlation > problems, but also reduces the number of interesting things you can > do with the database. Ever tried to hide a tank without first having > a bulldozer dig a big hole in the ground? This is related to the > polygon budget problem. Although dynamic terrain isn't currently available, at least in Simnet, to the best of my knowledge it isn't anymore inherently difficult in an IG than a workstation, it just hasn't been done (funded) yet. The same problems still exist for workstations and IG's, problems of broadcasting this data to the network, and updating other systems databases, or working from a common database. In any case there are many advantages to utilizing a CIG over a workstation, namely because they are built specificly for the purpose of generating and working within polygonaly represented worlds. There are some disadvantages as well. Such as, some systems don't offer a very friendly development environment for the end user, at least compared to what one may be use to on a workstation. But as VR system creators design their systems and evaluate their needs, I highly recommend at least considering an IG. It sounds as though UCF IST is working on some great projects, and I'm glad to see a none commercial interest coordinating standardization efforts. Also, I hope you don't mind that I have taken the liberty of forwarding the Distributed Simulation Workshop announcement to this list. --Jayson jraymond@bbn.com >--------------------------------------------------------------------- >Brian Blau, Visual Systems Scientist blau@ist.ucf.edu >Richard Dunn-Roberts, Visual Systems Scientist richard@ist.ucf.edu >--------------------------------------------------------------------- >Visual Systems Laboratory >Institute for Simulation and Training >University of Central Florida >12424 Research Parkway, Suite 300 >Orlando, FL 32826-3271 > >(407) 658 5073/5074 >--------------------------------------------------------------------- All disclaimers apply... |=============================|----------------------------------------| |== ======= ================| Jayson M. Raymond | |== ======= ================| jraymond@bbn.com | |== == == ==|----------------------------------------| |== === == === == === ==| BBN Systems and Technologies Corp. | |== === == === == === ==| Advanced Simulation Division | |== == == === ==| 14100 SE 36th St., Bellevue, Wa. 98006 | |=============================| Phone (206)746-6800 Fax (206)746-1335 | |=============================|----------------------------------------|