Graphics and Splines

[Anonymous]

How are splines drawn from graphics primitives?

[Alexander.Rivilis]

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@Anonymous wrote:

How are splines drawn from graphics primitives?

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Autodesk.AutoCAD.DatabaseServices.Spline class represent Spline entity.

[Anonymous]

Sorry, not sure that's what I'm looking for, should have gave more detail in the original post.

What I'm doing is using a drawable overrule and subentitytraits to fill closed entities that have certain xData.

Have it working for polylines, polyline2d, circles and ellipses by redrawing the entity with worlddraw.geometry.

I am stuck with splines. I don't know how to draw a spline with worlddraw.geometry.

[Alexander.Rivilis]

 It is only pseudo code:

public virtual bool WorldDraw(
    Drawable drawable, 
    Autodesk.AutoCAD.GraphicsInterface.WorldDraw wd
)
{
  using (Spline sp = new Spline()) {
   // Next setting spline value
   //....
   // Draw Spline
    wd.Geometry.Draw(spline);
  }
  return true;
}

[Anonymous]

Thanks for replying. I could do that part but I couldn't find how to fill the spline.

The other entities I redrew and using the graphics primitives.

I'm currently trying to generate a hatch on the fly to fill the spline 

[Alexander.Rivilis]

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@Anonymous wrote:

Thanks for replying. I could do that part but I couldn't find how to fill the spline.

The other entities I redrew and using the graphics primitives.

I'm currently trying to generate a hatch on the fly to fill the spline 

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I think it is easy to approximate spline with points and after using "graphics primitives" (for example, with help of Geometry.Polygon)

[Alexander.Rivilis · Accepted solution]

There is a sample:

using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Geometry;
using AcGi = Autodesk.AutoCAD.GraphicsInterface;

[assembly: CommandClass(typeof(Rivilis.MyCommands))]

namespace Rivilis
{
  public class MyCommands
  {
    [CommandMethod("SplineOver")]
    public void CmdSimpleOverrule()
    {
      if (_overrule == null)
      {
        _overrule = new SplineOverrule();
        Overrule.AddOverrule(RXClass.GetClass(typeof(Spline)), _overrule, false);
      }
      else
      {
        Overrule.RemoveOverrule(RXClass.GetClass(typeof(Spline)), _overrule);
        _overrule = null;
      }
      Document doc = Application.DocumentManager.MdiActiveDocument;
      doc.Editor.Regen();
    }
    private static SplineOverrule _overrule = null;
  }
  public class SplineOverrule : AcGi.DrawableOverrule
  {
    const double Fuzz = 1e-4;
    public override bool WorldDraw(AcGi.Drawable drawable, AcGi.WorldDraw wd)
    {
      base.WorldDraw(drawable, wd);
      Spline spline = drawable as Spline;
      if (spline != null)
      {
        using (NurbCurve3d curve3d = spline.GetGeCurve() as NurbCurve3d)
        {
          BoundBlock3d blk = curve3d.BoundBlock;
          double minChord = blk.GetMaximumPoint().DistanceTo(blk.GetMinimumPoint()) * Fuzz;
          PointOnCurve3d[] ptCurvs =
            curve3d.GetSamplePoints(curve3d.StartParameter, curve3d.EndParameter, minChord);
          using (Point3dCollection pts = new Point3dCollection())
          {
            foreach (PointOnCurve3d p in ptCurvs) pts.Add(p.GetPoint());
            wd.SubEntityTraits.FillType = AcGi.FillType.FillAlways;
            wd.SubEntityTraits.TrueColor = spline.Color.EntityColor;
            wd.Geometry.Polygon(pts);
          }
        }
      }
      return true;
    }
  }
}

[Anonymous]

Thanks. Will accept as solution since it gives better results than other methods I tried.

Tried hatching the spline and zooming to see how well it followed the spline - Much the same as your code.

Tried the following code - More accurate, but very slow to zoom or pan

 Using pts As New Point3dCollection
           For i = 0 To sp.EndParam
                   pts.Add(sp.GetPointAtParameter(i))
           Next
           wd.Geometry.Polygon(pts)
End Using

[Alexander.Rivilis]

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@Anonymous wrote:
 

...Tried the following code - More accurate, but very slow to zoom or pan...

 Using pts As New Point3dCollection
           For i = 0 To sp.EndParam
                   pts.Add(sp.GetPointAtParameter(i))
           Next
           wd.Geometry.Polygon(pts)
End Using

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You can change Fuzz value in my code (for example, 1e-6) in order to get more accuracy.