Get the point with the lowest x-value

Vijayaragavan,

Here is some sample code I use for getting lines and circles from an IGES file. You can expand this to handle any of the OCC primitive curve types. However, compound shapes like triangles and squares are another story. You would need to write code to look at a set of lines and identify the compound shapes. For example:
- find edges that form a closed loop (you might be able to look at wires in the OCC shape)
- if there are four edges
- if opposite edges have the same length
- if at least one angle is 90 degrees
- this must be a rectangle
- get the lengths of the edges for the dimensions

Other complex shapes can be more or less complicated. We have done some of this work, but it is too complicated to post and is proprietary to my company, so I can't share it. Sorry.

Good luck, here's the code,
Rob

// build a compound of edges to be converted
Bnd_Box bound;
Standard_Real minX, minY, minZ, maxX, maxY, maxZ;
BRep_Builder builder;
TopoDS_Compound compound;
builder.MakeCompound(compound);
TopExp_Explorer ex;
for (ex.Init(shape, TopAbs_EDGE); ex.More(); ex.Next()) {
// get the bounding box for this edge
bound.SetVoid();
BRepBndLib::Add(ex.Current(), bound);
bound.SetGap(0.0);

// if the edge is parallel to the Z axis, skip it
if (bound.IsVoid() ||
(bound.IsXThin(Precision::Confusion()) &&
bound.IsYThin(Precision::Confusion()))) continue;

// add the edge to the compound
builder.Add(compound, ex.Current());
}

// get the bounding box of the shape
bound.SetVoid();
BRepBndLib::Add(compound, bound);
bound.SetGap(0.0);
bound.Get(minX, minY, minZ, maxX, maxY, maxZ);

// get the maximum z plane minus a tolerance
Standard_Real zTop = maxZ-((maxZ-minZ)*BOX_TOL);

// make a map to avoid duplicate edges
TopTools_MapOfShape mapEdges;

// loop through the edges in the shape
for (ex.Init(compound, TopAbs_EDGE); ex.More(); ex.Next()) {
TopoDS_Edge edge = TopoDS::Edge(ex.Current());

// skip this edge if it was already processed
if (mapEdges.Contains(edge)) continue;

// get the bounding box for this edge
bound.SetVoid();
BRepBndLib::Add(edge, bound);
bound.SetGap(0.0);
bound.Get(minX, minY, minZ, maxX, maxY, maxZ);

// skip this edge if it is not in the top plane
if (minZ < zTop) continue;

// add the edge to the map
mapEdges.Add(edge);

// get the curve from the edge
Standard_Real fFirst, fLast;
Handle(Geom_Curve) curve = BRep_Tool::Curve(edge, fFirst, fLast);

// if the edge is 0 length, throw it away
if (IsEqual(fFirst, fLast)) continue;

// swap the parameters if the edge is reversed
if (edge.Orientation() == TopAbs_REVERSED) {
Standard_Real fTemp = fFirst;
fFirst = fLast;
fLast = fTemp;
}

// process the curve based on its type
Handle(Standard_Type) type = curve->DynamicType();
if (type == STANDARD_TYPE(Geom_Line)) {
Handle(Geom_Line) line = Handle(Geom_Line)::DownCast(curve);

// get its start and end points
gp_Pnt gPtStart = line->Value(fFirst);
gp_Pnt gPtEnd = line->Value(fLast);

// create a line primitive
.....
}
else if (type == STANDARD_TYPE(Geom_Circle)) {
Handle(Geom_Circle) circle = Handle(Geom_Circle)::DownCast(curve);

// make a 360 degree arc a circle
if ((fabs(fmod(fFirst, Standard_PI*2.0)) < ZERO_TOL) &&
(fabs(fmod(fLast, Standard_PI*2.0)) < ZERO_TOL)) {
// get the center and radius
gp_Circ gCirc = circle->Circ();
gp_Pnt gPtCenter = gCirc.Location();
float fRadius = (float) gCirc.Radius();

// create the circle primitive
......
}
else {
// get the start point, end point, and mid point
gp_Pnt gPtStart = circle->Value(fFirst);
gp_Pnt gPtEnd = circle->Value(fLast);
gp_Pnt gPtMid = circle->Value((fFirst+fLast)/2.0);

// create the arc primitive
......
}
}
else {
qDebug("Unrecognized curve: %s - %g, %g", type->Name(), fFirst, fLast);
}
}