topic Rotating a 3dPolyline in .NET Forum

Rotating a 3dPolyline

Anonymous — Mon, 08 Apr 2013 02:39:00 GMT

Hi,

I am trying to rotate a 3dPolyline, so that I can check(view) the Z-value of vertices in the top-view mode.

The following is the example which I am trying to achieve.

The white 3dPolyline has vertices at each intersecting point with the contour lines.

Each vertax has Z-value.

I want to rotate this white 3dPolyline in 3D, so that I can make the red 2dPolyline. (Z-value becomes Y-value)

And the start point of the white 3dPolyline becomes the left most point of the red line.

The end point of the white 3dPolyline becomes the right most point of the red line.

Currently, I am doing this by making a new 2dPolyline, manually inserting Z-values as Y-values.

But it looks like my code can be neater if I use TrnasformBy(Matrix3d.Projection).

Sadly, I am not good with Geometry, so it's bit hard for me to figure out how to use this Matrix3d.Projection.

Could anyone write me a quick code snippet to make this function? (preferably in C#)

Thank you in advance.

Re: Rotating a 3dPolyline

fenton_webb — Mon, 08 Apr 2013 22:15:56 GMT

can you post the DWG file maybe?

Re: Rotating a 3dPolyline

Anonymous — Wed, 10 Apr 2013 02:01:30 GMT

I found an another way around.

Rotating twice and displace it!! 😃

Polyline3d pl3d = ent as Polyline3d;

double a = MyMath.GetAzimuth(pl3d.StartPoint, pl3d.EndPoint);
Matrix3d mat = Matrix3d.Rotation(a - (Math.PI / 2), new Vector3d(0, 0, 1), pl3d.StartPoint);                                        
pl3d.TransformBy(mat);

Matrix3d mat2 = Matrix3d.Rotation(3 * Math.PI / 2, new Vector3d(1, 0, 0), pl3d.StartPoint);
pl3d.TransformBy(mat2);

Vector3d v = new Vector3d(basePnt.X - pl3d.StartPoint.X, basePnt.Y - pl3d.StartPoint.Y, basePnt.Z - pl3d.StartPoint.Z);
Matrix3d mat3 = Matrix3d.Displacement(v);
pl3d.TransformBy(mat3);

Thank you for your time anyway~ 😃

Re: Rotating a 3dPolyline

_gile — Wed, 10 Apr 2013 10:04:36 GMT

Hi,

A little too late...

Point3d startPnt = pl3d.StartPoint;
Vector3d vect = pl3d.EndPoint - startPnt;
double angle = vect.GetAngleTo(Vector3d.XAxis, Vector3d.ZAxis);
pl3d.TransformBy(
    Matrix3d.Displacement(basePnt - startPnt) *
    Matrix3d.Rotation(Math.PI / -2.0, Vector3d.XAxis, startPnt) *
    Matrix3d.Rotation(angle, Vector3d.ZAxis, startPnt));

Re: Rotating a 3dPolyline

Anonymous — Mon, 15 Apr 2013 00:32:53 GMT

Didn't know I can write it this simple.
Thank you very much~!