{"responseHeader":{"status":0,"QTime":3,"params":{"q":"{!q.op=AND}id:\"101810\"","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":[{"file_name_t":"Malley-A_Shading_Method.pdf","thumb_s":"/bf/72/bf72bd5c8e46ee950872031d9edd2e3793a3b216.jpg","oldid_t":"compsci 9923","setname_s":"ir_computersa","restricted_i":0,"format_t":"application/pdf","modified_tdt":"2016-05-25T00:00:00Z","file_s":"/f9/e4/f9e428ba44941695c5c2443816644ab0de289ae1.pdf","title_t":"Page 26","ocr_t":"14 Figure 2.3. The Nusselt analog: projection onto hemisphere and circle. A significant part of the radiosity solution computation time is spent calculating form factors. For a scene described by n surface polygons, O(n2 ) form factor values are calculated for the radiosity solution. Cohen and Greenberg have developed a method for calculating the necessary form factors [9], which involves several steps. A hemi-cube (right half cube) is placed in the interior of a polygon, with its surface broken into rows and columns of pixel-like squares (Figure 2.4). The polygon closest to the hemi-cube along the direction from the center of the hemi-cube to the center of a given square on the hemi-cube surface is recorded, through a process similar to raster scan conversion. After the projection onto the hemi-cube is completed for all the polygons in the scene, the projected areas on the hemi-cube are converted into form factor values. The factors used to map the hemi-cube areas to form factor contributions are called delta form factors. Figure 2.5 is a summary of the hemi-cube form factor calculation algorithm. Form factor calculation is costly. Citing two cases, Cohen and Greenberg report","id":101810,"created_tdt":"2016-05-25T00:00:00Z","parent_i":101866,"_version_":1679953745191895042}]},"highlighting":{"101810":{"ocr_t":[]}}}