In AutoCAD we have the “DONUT” command, however there is no such entity as a donut. A donut is simply a LWPOLYLINE (AcDbPolyline) with two segments. Each segment has a bulge of 1.0 and the start point of one segment is the end point of the other segment. In addition the AcDbPolyline will have with and is also a close polyline. The following code fragment demonstrates a single ‘donut’, please note error checking is minimal: Note the arguments to ‘addVertextAt()’ which are the index, vertex location, bulge factor, starting width and ending width.
static void ADSProjectDonut(void)
{
// Using fixed values to simplify the code sample.
// Accept input for these values if required.
ads_real innerDiameter = 5.0;
ads_real outerDiameter = 15.0;
AcGePoint2d centerPoint(20.0, 20.0);
// Donut thickness
double width = (outerDiameter – innerDiameter) / 2.0;
// Start point of the polyline
AcGePoint2d sp
= centerPoint –
AcGeVector2d::kXAxis * (innerDiameter + width) / 2.0;
// End point of the polyline
AcGePoint2d ep
= centerPoint +
AcGeVector2d::kXAxis * (innerDiameter + width) / 2.0;
AcDbDatabase *pDb
= acdbHostApplicationServices()->workingDatabase();
AcDbBlockTableRecordPointer pMS
(
acdbSymUtil()->blockModelSpaceId(pDb),
AcDb::kForWrite
);
AcDbPolyline *pDNut = new AcDbPolyline();
double bulge = 1.0;
Acad::ErrorStatus es;
es = pDNut->addVertexAt(0, sp, bulge, width, width);
es = pDNut->addVertexAt(1, ep, bulge, width, width);
pDNut->setClosed(Adesk::kTrue);
es = pMS->appendAcDbEntity(pDNut);
if(es != Acad::eOk)
{
delete pDNut;
}
pDNut->close();
}
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