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This paprr presents inethoi-ls to compuie the locils of nll viewpoints froin which feoturcrs on known polyhedral nhjecls con be viewed in their entirety without being nccluAcd by ailything in ihe eizvironrni?nt. Convcx and coiicavc polyhedra with or withorit holes mid the viewing inndel of perspective projection are eniploycd in this work. h s r d on properties that are dcterrnincd (,f ihe occlusionfree nnd occItiAed loci of viewpoints, two tnethod,r to construct tlie!sc loci together with iheir cninplmity nnalysi%s nre preseriicd. I n the first inerhod, a hounilory rqwesentntion of thc occlii.rioizfree locus i.s ohtnincd. In the second ineihod, thr locus of occluded viewpoints is expressed in terms of a construciive solid geornc.try (CSG) representntion t h n~ cnnsisis of a union ?f coniponent so1id.s. Iinplementation results are shown. I n trodrictioii Wlicti attempting to view a feature of an object from a particular viewpoint, it may happen that some or all points of tlie feature may be occluded by either some part of the object on which it lies, or by other objects in (he environment. 111 this paper, we shall determine the viewpoints liom whicli object features of interest are visible in their entirety in a knowrr polyhedral world. 'I hat is, the features are not occluded by anything in the environment. O w approach has coinmon poiilly with research in the at ea of aqpect graphs [S, 9, lo]. Aspect graphs provide a parlition of' tlircc-dimerisional space iiito sets of viewpoints yielding topologically equivalent views aticl in this sense drfitte a twoader problem. J'his paper cniphasizes that tlie visibility pioldem should be viewed in its own riglit rathrr than as a spccial case of (tie more peticral aspect graph problem. Among the difkrences hetueen the work reportrd liet e and that of aspect graph reseat cli iricludc hie followitig: The pnrccllatiori of viewp4iit

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