QCAD Bugtracker

  • Status Assigned
  • Percent Complete
    0%
  • Task Type Feature Request
  • Category QCAD (main)
  • Assigned To
    Andrew
  • Operating System All
  • Severity Low
  • Priority Very Low
  • Reported Version 3.13.1
  • Due in Version Undecided
  • Due Date Undecided
  • Votes
  • Private
Attached to Project: QCAD Bugtracker
Opened by Pero Brbora - 01.04.2016
Last edited by Andrew - 06.05.2016

FS#1407 - Splines: add support for knot weights, start-, end tangents

Attached DWG/DXF files are incorrectly read by QCAD.
They contain splines drawn using ZWCAD and saved as DWG/DXF version 2000.
Above splines are polylines created with autolisp routine which converts spline to polyline, so you can see how splines should actually be drawn.

First spline is created with fit points: 2,2 4,4 6,2
Then copied and applied weight of 2 on central control point.
Then copied again and applied weight of 0.5 on central control point.

Second spline is created with fit points: 6,2 8,4 10,2 with vertical start and end tangent.
Then copied and applied fit tolerance of 1 for fit points.

Third spline is created with fit points: 10,2 12,4 14,2 with horizontal start and end tangent.

Fourth and fifth spline are correctly drawn by QCAD.

Link to bitmap (converted to png) export:
External Link

Versions
QCAD version: 3.13.1.0
Date: Mar 17 2016
Qt version: 4.8.4
Compiler version: gcc 4.4.3
Build Date: Mar 17 2016
Revision:
Architecture: x86_64
OS: Linux
OS version: Unknown

Admin
Andrew commented on 01.04.2016 18:41

I can confirm that fit points / knots with a weight other than 1 are currently not supported by QCAD. All fit points / knots are treated as if they have an equal weight.

Pero Brbora commented on 02.04.2016 10:43

Not supporting weights (they are related to control points) is fine, not many users actually use them.

From what I can see, QCAD creates splines from fit points only (start/end tangent not respected), you would get better results if you create splines from control points and knots. Is this true?

Admin
Andrew commented on 04.04.2016 07:43
QCAD creates splines from fit points only (start/end tangent not respected), you would get better results if you create splines from control points and knots.

You can create splines from fit points or from control points:
Draw > Spline > Spline (fit points)
Draw > Spline > Spline (control points)

When files are loaded, fit points are used whenever available. You might be able to convert the spline with fit points to a spline with control points / knots in the source application.

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