Author Topic: Non-uniformly scaled Matrix3d  (Read 2532 times)

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  • Newt
  • Posts: 188
Non-uniformly scaled Matrix3d
« on: June 22, 2011, 08:58:21 AM »
For some reason, the Autodesk.AutoCAD.Geometry.Matrix3d struct does not have any methods to non-uniformly scale the axes.  It only provides a Scaling(double scaleAll, Point3d center) method to create a uniform scaleing matrix.  So I created a method to get back a non-uniform scaling matrix and use it for point transformations, but something is not right.

Code: [Select]
       public static Matrix3d ScaleMatrix(double xScale, double yScale, double zScale, Point3d origin)
            return Matrix3d.Identity
                           .PostMultiplyBy(new Matrix3d(new double[] { xScale, 0.0, 0.0, 0.0,
                                                                       0.0, yScale, 0.0, 0.0,
                                                                       0.0, 0.0, zScale, 0.0,
                                                                       0.0, 0.0, 0.0, 1.0 }))

        public static Matrix3d ScaleMatrix(Scale3d scaling, Point3d origin)
            return ScaleMatrix(scaling.X, scaling.Y, scaling.Z, origin);

        public static Point3d Transform(this Point3d point, Point3d displacement, Scale3d scaling, double rotation)
            Matrix3d transform = Matrix3d.Identity
                                         .PostMultiplyBy(ScaleMatrix(scaling, Point3d.Origin))
                                         .PostMultiplyBy(Matrix3d.Rotation(rotation, Vector3d.ZAxis, Point3d.Origin))

            return point.TransformBy(transform);

What have I done wrong?
« Last Edit: June 22, 2011, 09:02:56 AM by zoltan »


  • Water Moccasin
  • Posts: 1864
Re: Non-uniformly scaled Matrix3d
« Reply #1 on: June 23, 2011, 08:55:46 PM »
public static Matrix3d scaleMatrix(double x,double y,double z,Point3d cen)
            if (x == y && x == z) return Matrix3d.Scaling(x, cen);
            double[] data={x,0,0,cen.X,0,y,0,cen.Y,0,0,z,cen.Z,0,0,0,1};
            Matrix3d m = new Matrix3d(data);
            return m;
Perhaps this is better. It looks like you are scaling the number zero


  • Guest
Re: Non-uniformly scaled Matrix3d
« Reply #2 on: June 27, 2011, 06:34:52 AM »
I encountered the same problem last week, when I was trying to scale a BlockReference with different scaling factors.
I also build my own matrix, but scaling an entity is only allowed with uniformed scale factors.

However, if you want to scale a BlockReference with different scale factors you should try this:

Code: [Select]
' Scale the blockreference
' We can't use TransformBy in this case, because we might have different scaling factors here.
Dim br as BlockReference
br.ScaleFactors = New Scale3d(xScale, yScale, zScale)