Importance

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Abstract

The visibility ordering of polyhedral cells is efficiently determined by building an ordering graph, comprising oriented edges between two cells. Each edge (A,B) corresponds to the fact that cell A has to be projected, or rendered, before B. A set of ordering relations and rules that can be shown to generate, if one exists, a global ordering of the polyhedral cell complex. Three different types of edges are used to accomplish this: MPVO, BSP and PPC edges. MPVO edges exist between two cells that share a face. To define the BSP edges, a BSP-tree of the boundary faces of the cell complex is constructed. During this construction, some of the boundary faces of the cells will be `cut` by the BSP-tree `extended` faces, into multiple pieces. If C is the boundary cell, and c', c', and so on, are the pieces of its boundary faces, the BSP_edge (c', C) is defined to mean that cell C can only be projected after c' has been projected by the BSP. A cell C is in the PPC if one of the pieces that compose it, say c', has been projected by the BSP, but there exist other pieces of cell C that have not been projected. In this case, additional checks are done to ensure cells are not being projected out of order. This is accomplished by performing `ray shooting`.

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First Claim