| | A framework to compute a shape as seen in a projection plane. This is done by
calculating the visible and the hidden parts of the shape.
HLRBRep_Algo works with three types of entity:
- shapes to be visualized
- edges in these shapes (these edges are
the basic entities which will be visualized or hidden), and
- faces in these shapes which hide the edges.
HLRBRep_Algo is based on the principle of comparing each edge of the shape to be
visualized with each of its faces, and calculating the visible and the hidden parts of each edge.
For a given projection, HLRBRep_Algo calculates a set of lines characteristic of the
object being represented. It is also used in conjunction with the
HLRBRep_HLRToShape extraction utilities, which reconstruct a new, simplified shape
from a selection of calculation results. This new shape is made up of edges, which
represent the shape visualized in the projection.
HLRBRep_Algo takes the shape itself into account whereas HLRBRep_PolyAlgo
works with a polyhedral simplification of the shape. When you use HLRBRep_Algo, you
obtain an exact result, whereas, when you use HLRBRep_PolyAlgo, you reduce
computation time but obtain polygonal segments. In the case of complicated
shapes, HLRBRep_Algo may be time-consuming.
An HLRBRep_Algo object provides a framework for:
- defining the point of view
- identifying the shape or shapes to be visualized
- calculating the outlines
- calculating the visible and hidden lines of the shape.
Warning
- Superimposed lines are not eliminated by this algorithm.
- There must be no unfinished objects inside the shape you wish to visualize.
- Points are not treated.
- Note that this is not the sort of algorithm used in generating shading, which
calculates the visible and hidden parts of each face in a shape to be visualized by
comparing each face in the shape with every other face in the same shape.
More...
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1.6.3