Brep derived from Flat Bounding Box cannot do any methods.

Hi! I recently face a weird problem when trying to do brep methods. The brep is from flat bounding box.

Curve planarcurve = c;
BoundingBox bbox= planarcurve.GetBoundingBox(true);
Brep b_bbox = bbox.ToBrep();
Print(b_bbox .ToString()); //_________ this line gives me error
double d = b_bbox.GetArea();//______ same error

The error says: Object reference not set to an instance of an object. (line: 4) The goal is to get the area of the flat bounding box.

Any advice is appreciated! Thanks

Replies to This Discussion

Permalink Reply by yehezkielwm on March 15, 2017 at 2:15am

Here is the screenshot of the problem. I need to do area calculation of the flat boundingbox in C#.

Permalink Reply by yehezkielwm on March 15, 2017 at 2:41am

Update 1.

Figured out a "temporary" way of solving it by making Polyline of the flat box vertices. Pretty sure it only works to calculate base area of the bounding box. Any advice is appreciated :)

Curve planarcurve = x;
BoundingBox bbox = planarcurve.GetBoundingBox(true);
Point3d[] pts = bbox.GetCorners();
Point3d[] pt_ar = new Point3d[5]{pts[0],pts[1],pts[2],pts[3],pts[0]};
Polyline plln = new Polyline(pt_ar);
Brep b_bbox = Brep.CreatePlanarBreps(plln.ToNurbsCurve())[0];
A = b_bbox.GetArea(); //works now

Permalink Reply by David Rutten on March 15, 2017 at 2:30am

A flat boundingbox would result in an invalid brep, because four of the six sides would have zero area and coincident edges. Grasshopper specifically handles this case and creates a single plane surface instead.

However you can calculate the area of a boundingbox far more efficiently than from a brep. If you know your box is flat, all you have to do is multiply the difference in X and Y of the Min and Max points.

Permalink Reply by yehezkielwm on March 15, 2017 at 2:44am

Wow that is nifty. Thanks David!

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