Broken PLT(HPGL) lines on re-importing, PLT(HPGL) exports from very high node count SVG files in CorelDraw GS X4 & X6

Question

I have SVG files which i import into CorelDraw for exporting them into PLT/HPGL files.

The SVG files are polygons with extremely high node counts - up to 10000 nodes sometimes.

When i export them to PLT through Corel or Inkscape the lines are sometimes broken. The breaks are visually invisible. The drawing looks the same but when i zoom in there are places where a node or 2 are missing - tricking my laser cutter into thinking that they are not single continouos lines.

I do not want to join the lines or simplify the nodes using either of those programs.

I am building a program that exports those polygons and i want to know what is going wrong - there must be some restrictions on HPGL/PLT file format - so that i can configure my program to output a correct path that can be exported without those issues.

UPDATE: The issue seems, and i say again SEEMS to be in the IMPORT of the PLT files.

When i export a PLT file from Corel and import it again in INKSCAPE it looks OK.

However when i re-import the exported PLT's into Corel the problem is there.

Anyone else had this problem?

Answer 1

I am answering my own question.

There's an actual bug in version X4 and X6 of CorelDraw GS when it comes to PLT imports.

The bug happens only when there is an extremely high count of nodes in a path.

I have filed a bug report with Corel's Paid Support and i am awaiting for answers.

A workaround if you are in the same situation is to reduce the node count by using Corel's Reduce Nodes function that you can access by exposing the nodes in the drawing(Shape Tool), then select all nodes using the appropriate flyout button(that appears when you expose the nodes) and click on Reduce Nodes. This is curve approximation and distorts a little the shape you had before(it smoothes it out). It is however quite accurate, albeit it reduces significantly the node count up to 8-10x(you can choose how much you reduce the nodes) and also it distorts at a small level the original shape. The polygon is turned into a curvy path where appropriate. When all this is done CorelDraw can re-import the (reduced nodes) exported PLT just fine.

This workaround has been tested ONLY on CorelDraw GS X6.

This is a workaround and NOT the right solution.

The right solution is for CorelDraw to fix the bug itself, since it is a bug and not a fault of the PLT format specification itself.

Another solution is importing the exported PLT into Inkscape which processes it just fine. However the CorelDraw exported PLT must not be re-imported and re-exported into CorelDraw since it will break upon re-importing(due to the bug) and it will be re-exported broken.

The workaround i described has also been suggested by Corel's Tech Support, but i replied that this is not a solution but a workaround and that they should contact their Software Development team and get back to me.

I will post the reply and proposed solution they will give me HERE as soon as i have one.

Hope this helps.