Function to get a list of points of overapped areas from a list of Points of two Polygons

[AhsinChoudhry786]

Which API function I can use to get a list of points of overapped area(s) from a list of Points of two Polygons? Thanks

[sethhillbrand]

Are you asking to only get vertices that exist already? So, for example the attached image would have no overlapping points

Or, are you wanting to return the vertices that represent the polygon where the two areas overlap like the dark green polygon attached

[AhsinChoudhry786]

Yes, I want the function to return the vertices that represent the Polygon where two areas overlap.

[sethhillbrand]

Then, I think you want the example from this page: http://www.angusj.com/clipper2/Docs/Units/Clipper/Functions/Intersect.htm

[AhsinChoudhry786]

I have created a function to get a list of points of overlapped shape from a list of points of two shapes but for some reason its giving incorrect points of the output shape.

#define ADD(A,X,Y) A.push_back(Point64(int64_t(X), int64_t(Y)))

EXTERN_DLL_EXPORT const char* PointsInsidePolygon(TPoint* ShapeA, LONG ShapeANumPoints, TPoint* ShapeB, LONG ShapeBNumPoints, TPoint*& OutputShape, LONG& OutputShapeNumPoints)
{
Path64 a, b;

for (int p = 0; p < ShapeANumPoints; p++)
{
    ADD(a, ShapeA[p].XY.x, ShapeA[p].XY.y);
}

for (int p = 0; p < ShapeBNumPoints; p++)
{
    ADD(b, ShapeB[p].XY.x, ShapeB[p].XY.y);
}

const int m = 10;
for (size_t i = 0; i < a.size(); i++) { a[i].x /= m; a[i].y /= m; b[i].x /= m, b[i].y /= m; }

Paths64 AA; AA.push_back(a);
Paths64 BB; BB.push_back(b);
Paths64 solution = Intersect(Paths64(AA), Paths64(BB), FillRule::NonZero);

size_t SizeAA = AA.size();
size_t SizeBB = BB.size();

OutputShapeNumPoints = 0;

for (int s = 0; s < solution.size(); s++)
{
    Path64 sol = solution[s];
    OutputShapeNumPoints = (LONG)sol.size();

    OutputShape = new TPoint[OutputShapeNumPoints];

    for (int ss = 0; ss < OutputShapeNumPoints; ss++)
    {
        Point pt = sol[ss];
        TPoint pts;
        pts.XY.x = (LONG)pt.x;
        pts.XY.y = (LONG)pt.y;
        
        OutputShape[ss] = pts;
    }
}

return CLIPPER2_VERSION;

}

[AhsinChoudhry786]

Then, I think you want the example from this page: http://www.angusj.com/clipper2/Docs/Units/Clipper/Functions/Intersect.htm

I have created a function to get a list of points of overlapped shape from a list of points of two shapes but for some reason its giving incorrect points of the output shape.

EXTERN_DLL_EXPORT const char* PointsInsidePolygon(TPoint* ShapeA, LONG ShapeANumPoints, TPoint* ShapeB, LONG ShapeBNumPoints,
TPoint*& OutputShape, LONG& OutputShapeNumPoints)
{
Path64 a, b;

for (int p = 0; p < ShapeANumPoints; p++)
{
    ADD(a, ShapeA[p].XY.x, ShapeA[p].XY.y);
}

for (int p = 0; p < ShapeBNumPoints; p++)
{
    ADD(b, ShapeB[p].XY.x, ShapeB[p].XY.y);
}

const int m = 10;
for (size_t i = 0; i < a.size(); i++) { a[i].x /= m; a[i].y /= m; b[i].x /= m, b[i].y /= m; }

Paths64 AA; AA.push_back(a);
Paths64 BB; BB.push_back(b);
Paths64 solution = Intersect(Paths64(AA), Paths64(BB), FillRule::NonZero);

size_t SizeAA = AA.size();
size_t SizeBB = BB.size();

OutputShapeNumPoints = 0;

for (int s = 0; s < solution.size(); s++)
{
    Path64 sol = solution[s];
    OutputShapeNumPoints = (LONG)sol.size();

    OutputShape = new TPoint[OutputShapeNumPoints];

    for (int ss = 0; ss < OutputShapeNumPoints; ss++)
    {
        Point pt = sol[ss];
        TPoint pts;
        pts.XY.x = (LONG)pt.x;
        pts.XY.y = (LONG)pt.y;
        
        OutputShape[ss] = pts;
    }
}

return CLIPPER2_VERSION;

}