bugGNU Octave - Bugs: bug #41294, FLTK does not draw linewidths...


bug #41294: FLTK does not draw linewidths >= 6 correctly

Submitted by:  Rik <rik5>
Submitted on:  Tue 21 Jan 2014 10:56:25 PM UTC  
Category:  Plotting with OpenGL Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Incorrect Result
Status:  Invalid Assigned to:  None
Originator Name:  Open/Closed:  Closed
Release:  dev Operating System:  GNU/Linux

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Sun 20 Apr 2014 12:48:11 PM UTC, comment #4: 

One possible solution would be to render lines as quad when the linewidth is above a given value.

Michael Goffioul <goffioul>
Sun 20 Apr 2014 02:23:30 AM UTC, comment #3: 

I found the problem.  The issue is that OpenGL itself only supports a limited range of line widths.  It has a range both for aliased (jagged) and anti-aliased (smooth) lines.

I've attached code which will print out these ranges.  Unfortunately it's in C so you need to have the development packages for GL, GLU, and GLUT installed.  On Linux it compiles with

gcc -o rpt_lwidth rpt_lwidth.c -lGL -lGLU -lglut

In my case, the range of smooth lines is 1.0-5.0 and the granularity is 0.5 so I can really have lines from 0.5-5.5 which explains the issue.

I don't think there's much to be done about this so I'm closing the report.

(file #31215)

Rik <rik5>
Project Administrator
Tue 18 Feb 2014 04:16:49 PM UTC, comment #2: 

Anti-aliasing neither helps nor hurts, but the lines are still not drawn correctly above 5.

Rik <rik5>
Project Administrator
Sun 16 Feb 2014 09:30:57 PM UTC, comment #1: 
Felipe G. Nievinski <fgnievinski>
Tue 21 Jan 2014 10:56:25 PM UTC, original submission:  

Run the attached script mk_linewidths to generate a table of lines where the linewidth is equal to the y-value.  For linewidths greater than 5, Octave just draws a width=5 line.  See the attached pictures made with the FLTK and gnuplot toolkit.  gnuplot correctly keeps growing the line as the linewidth is increased.  Also, note that this is only an on-screen drawing issue.  Printing the plot to a file, which uses gl2ps, correctly scales the line.

Rik <rik5>
Project Administrator


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Attach Files:

Attached Files
file #31215:  rpt_lwidth.c added by rik5 (907B - text/x-c)
file #30330:  mk_linewidths.m added by rik5 (169B - d2l/unknowntype)
file #30331:  gnuplot_linewidths.png added by rik5 (8KiB - image/png)
file #30332:  fltk_linewidths.png added by rik5 (12KiB - image/png)


Depends on the following items: None found

Items that depend on this one: None found


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    Follow 6 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2014-04-20 rik5 Attached File- => Added rpt_lwidth.c, #31215
        StatusConfirmed => Invalid
        Open/ClosedOpen => Closed
    2014-01-21 rik5 Attached File- => Added mk_linewidths.m, #30330
        Attached File- => Added gnuplot_linewidths.png, #30331
        Attached File- => Added fltk_linewidths.png, #30332

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