How to get the direction of ellipse?

huangyhg

Hi,

How to get the direction of ellipse? Is the default direction as counter clockwise for ellipse?

I found that start point and end point were not specified by counter clockwise rule (the direction of rotation from start point to end point) when I get start point and end point of ellipse.

I cannot get the direction of partial ellipse according to the following code.

Code:

// get the ellipse data

LPDISPATCH dStartPnt = swSketchEllipse.GetStartPoint2();

LPDISPATCH dEndPnt = swSketchEllipse.GetEndPoint2();

LPDISPATCH dCenterPnt = swSketchEllipse.GetCenterPoint2();

LPDISPATCH dMajorPnt = swSketchEllipse.GetMajorPoint2();

LPDISPATCH dMinorPnt = swSketchEllipse.GetMinorPoint2();

yanhua

huangyhg

The start point position is incorrect when partial ellipse is drawn with clockwise in SolidWorks. Because the start point do not specified by counter clockwise rule. By now, I think that this is a bug of partial ellipse if I can not get the direction of ellipse.

You provide two parameters as start point and end point which do not specified by counter clockwise rule at all. If I draw partial ellipse with clockwise in SolidWorks, I only get the start point with clockwise via SW API. In other words, I get the incorrect result for the start point via SolidWorks API. If you do not tell the direction of partial ellipse, I expect to get the start point specified by the constant rule as counter clockwise in all situcations.

yanhua

huangyhg

Dear Yanhua,

In 2007 there is a new method, SketchEllipse::GetRotationDir, to get the direction.  If you're using 2006 or later, the information below may help:

The direction of an arc is usually defined by looking in the opposite direction along this normal, going in a CCW direction from start to end point.

> Suppose, we have an arc with start angle 10 degree and end angle = 100 degree.
> Now for this arc if the direction is Counter clock wise then Arc angle
> is 90 degree and if the arc is clockwise the arc angle is 270 degree.

Regards,
Robin Richter