We describe an adaptive display algorithm for interactive frame rates during visualization of very complex virtual environments. The algorithm relies upon a hierarchical model representation in which objects are described at multiple levels of detail and can be drawn with various rendering algorithms. The idea behind the algorithm is to adjust image quality adaptively to maintain a uniform, user-specified target frame rate. We perform a constrained optimization to choose a level of detail and rendering algorithm for each potentially visible object in order to generate the "best" image possible within the target frame time. Tests show that the algorithm generates more uniform frame rates than other previously described detail elision algorithms with little noticeable difference in image quality during visualization of complex models.

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The number of polygons comprising interesting architectural models is many more than can be rendered at interactive frame rates. However, due to occlusion by opaque surfaces (e.g., walls), only a small fraction of atypical model is visible from most viewpoints.We describe a method of visibility preprocessing that is efficient andeffective foraxis-aligned oril.ria/ architectural m[}dels, A model is subdivided into rectangular cc//.$ whose boundaries coincide with major opaque surfaces, Non-opaque p(~rtc~/.rare identified rm cell boundaries. and used to form ana~ju{~'n~y,q)f~/>//con nectingthe cells nfthesubdivisicm.Next. theccl/-r/~-cc// visibility is computed for each cell of the subdivisirrn, by linking pairs of cells between which unobstructed .si,q/~t/inr.~exist.During an interactive ww/krhrm/,q/~phase, an observer with a known~~sition and\it)M~~~)~t>mov esthrc>ughthe model.At each frame, the cell containingthe observer is identified, and the contents {] fp{>tentially visible cells areretrieved from storage. The set of potentially visible cells is further reduced by culling it against theobserver's view cone, producing the~)yt>-r~]-t(>//\ i,$ibi/ify, The contents of the remaining visible cells arc then sent to a graphics pipeline for hidden-surface removal and rendering, Tests onmoderatelyc mnplex 2-D and 3-D axial models reveal substantially reduced rendering loads, CR Categrsries and Subject Descriptors: [Computer {;raphics]: l.3.5Compuiational GeonletW and Object Model ing-,qe~~~~~efri( a (,qorilhnf.j, /fthis material isgrantcd provided that the copies are not made or distributed for direct commercial advantage, the ACM copyright notice mrd the title of the fsubl icatitrn and ih date appear. and notice is given that copying is by permission ,,( the Association for Comput ing Machinery. To copy otherwise, ormrcpuh[ish. requmcs a fee mrd/orspec itic pm-mission.ACM-O-X9791-436-WI m)7mrl I KS) 75