topic Re: pRegion->getAreaProp() in ObjectARX Forum

pRegion->getAreaProp()

EMD1954 — Mon, 17 Jun 2013 20:26:27 GMT

I want to let the user draw a complicated, 2D polyline, select it, and have it convert to a region so I can use the mass properties for a handful of tasks. I've gotten to the point (following the samples) where I am able to create the region using

es = AcDbRegion::createFromCurves(curveSegs, regions);

AcDbRegion *pRegion;

pRegion =static_cast<AcDbRegion*>(regions[0]); // I only have one element to pick

pRegion->getPlane(plane);

plane.getCoordSystem(origin, xAxis, yAxis);

es = pRegion->getAreaProp(origin, xAxis, yAxis, perimeter, area, centroid, momInertia,

prodInertia, prinMoments, prinAxes, radiiGyration, extentsLow, extentsHigh);

Then I save it to the database. It works fine up to this point, but I get the wrong centroid (and different than the command line "MASSPROP")

Anything obvious? Any help would be appreciated.

Thanks,

Re: pRegion->getAreaProp()

owenwengerd — Tue, 18 Jun 2013 01:59:41 GMT

What are the actual values that you're passing for the origin, xAxis, and yAxis arguments to getAreaProp()? Perhaps the MASSPROP command uses the UCS instead of the World coordinate system.

Re: pRegion->getAreaProp()

EMD1954 — Mon, 24 Jun 2013 17:07:01 GMT

Origin is -50.1250, 76.0000, 0.0000 (it's the first point of the 3Dpoly that i created before it's turned into a region)
xAxis is 1.0000, 0.0000, 0.0000
yAxis is 0.0000, 1.0000, 0.0000

Function is attached as .txt file

Thanks,

Re: pRegion->getAreaProp()

owenwengerd — Mon, 24 Jun 2013 23:57:43 GMT

Try the WCS or UCS, then compare the results to MASSPROP.

Re: pRegion->getAreaProp()

EMD1954 — Tue, 25 Jun 2013 13:16:23 GMT

Sorry for the trouble, but I don't understand. I tried it in the "world" UCS, changed the view and set the UCS to "View" and even tried to set the UCS to "element". What do you mean? Sorry.

Re: pRegion->getAreaProp()

owenwengerd — Tue, 25 Jun 2013 14:13:42 GMT

I am referring to the first three arguments to getAreaProp(). For example, the WCS would be:

pRegion->getAreaProp(AcGePoint3d(0,0,0), AcGeVector3d(1,0,0), AcGeVector3d(0,1,0), ...);

Re: pRegion->getAreaProp()

EMD1954 — Tue, 25 Jun 2013 17:27:11 GMT

Yes. The problem was that "origin" was returning the first point of the original polyline, so I just zeroed the X and Y coordinates (I need Z for the proper elevation). The xAxis and yAxis were correct:

pRegion->getPlane(plane);

plane.getCoordSystem(origin, xAxis, yAxis);

origin.x = 0.0;

origin.y = 0,0;

Works great - thank you,