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-- File: HLRBRep_Algo.cdl
-- Created: Wed Aug 3 16:15:26 1994
-- Author: Christophe MARION
-- <cma@ecolox>
---Copyright: Matra Datavision 1994
class Algo from HLRBRep inherits InternalAlgo from HLRBRep
---Purpose: 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.
uses
TShared from MMgt,
Shape from TopoDS
is
Create returns mutable Algo from HLRBRep;
---Purpose: Constructs an empty framework for the
-- calculation of visible and hidden lines of a shape in a projection.
-- Use the function:
-- - Projector to define the point of view
-- - Add to select the shape or shapes to be visualized
-- - Update to compute the outlines of the shape, and
-- - Hide to compute the visible and hidden lines of the shape.
Create(A : Algo from HLRBRep) returns mutable Algo from HLRBRep;
Add(me : mutable; S : Shape from TopoDS;
SData : TShared from MMgt;
nbIso : Integer from Standard = 0)
---Purpose: add the Shape <S>.
is static;
Add(me : mutable; S : Shape from TopoDS;
nbIso : Integer from Standard = 0)
---Purpose: Adds the shape S to this framework, and
-- specifies the number of isoparameters nbiso desired in visualizing S.
-- You may add as many shapes as you wish. Use the function Add once for each shape.
is static;
Index(me : mutable; S : Shape from TopoDS)
returns Integer from Standard
---Purpose: return the index of the Shape <S> and
-- return 0 if the Shape <S> is not found.
is static;
OutLinedShapeNullify(me : mutable)
---Purpose: nullify all the results of OutLiner from HLRTopoBRep.
is static;
end Algo;
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