Elipse

Just out of curiosity, did either the sketch area or face area match what you came up with manually?

"Seth Renigar" wrote in message news:haO_f.106865$ snipped-for-privacy@tornado.southeast.rr.com...

Alex,

Since there is no exact formula for the perimeter of an ellipse, it could be that your calculation is less accurate than SolidWorks. This site has a discussion and various series and approximations that are much better than some others I found:

I tried three ellipses, with eccentricities of 1.111, 2.5 and 10 and the perimeter values were all within a few hundredths of a percent of Ramanujan's first formula, which is probably within the error of the formula. The areas though were off by up to a third of a percent. This is very interesting, because the area equation is exact. I guess SolidWorks is calculating the area based on the curve values. Either the curve locations are off a bit or there area calculation is not terribly accurate.

Seth,

On my test ellipses, the sketch area values were always closer than the face values. Since the perimeter values are the same in the sketch and in the model, why are the areas different? Did different people use different methods to calculate the area in the two cases?

Jerry Steiger Tripod Data Systems "take the garbage out, dear"

Maybe different alogrithms or; surface / solid analysis usually reference a tessellated version of the model. Area properties may use the same methods but at different resolutions. Just a bit of idle speculation...