{"responseHeader":{"status":0,"QTime":4,"params":{"q":"{!q.op=AND}id:\"96060\"","hl":"true","hl.simple.post":"","hl.fragsize":"5000","fq":"!embargo_tdt:[NOW TO *]","hl.fl":"ocr_t","hl.method":"unified","wt":"json","hl.simple.pre":""}},"response":{"numFound":1,"start":0,"docs":[{"modified_tdt":"2015-11-02T00:00:00Z","thumb_s":"/14/79/14792290ef8d25afa63936a6e25539def97d04f7.jpg","oldid_t":"compsci 3878","setname_s":"ir_computersa","file_s":"/be/8e/be8e05b7f5b43f248333b02cc993f41125c2027f.pdf","title_t":"Page 22","ocr_t":"12 2.2 View-based Methods In the view-based approach, pixel images of the stock and of the cutting tool are generated from one specific viewing angle and the process of material removal is simulated through boolean volume subtraction operations in the image-space. The following subsections describe work done at three different places in this direction. 2.2.1 Wang's System Wang and Wang [6] have implemented a system that uses an analytic method to find envelopes of volumes swept by the cutting tool and that maintains a depth buffer to represent the part being machined. The mathematical model for finding the swept volume is described as follows. Let G be a moving solid (also called a generator). The volume S, swept by G can be expressed as where Gi(t) is the instance of the moving solid at timet. In general, it is very hard to construct the swept volume by doing a union of primitives. An alternative approach is to compute its boundary surface, also known as the envelope surface. The envelope consists of two kinds of surfaces. 1. the subset of the boundary of the generator at the initial and final positions 2. the new surfaces created by the silhouette of the generator during the motion The first kind of surfaces mentioned above is handled in existing solid modeling systems. The second category is discussed here. A family of surfaces can be represented by the implicit equation F(x, y, z, t) = 0","restricted_i":0,"id":96060,"created_tdt":"2015-11-02T00:00:00Z","format_t":"application/pdf","parent_i":96117,"_version_":1642982571802361857}]},"highlighting":{"96060":{"ocr_t":[]}}}