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Re: plotted circle is regular decagon on opengl graphics
From: |
Andreas Weber |
Subject: |
Re: plotted circle is regular decagon on opengl graphics |
Date: |
Thu, 11 Aug 2016 10:12:37 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Icedove/45.1.0 |
Hi Tatsuro,
Am 11.08.2016 um 08:17 schrieb Tatsuro MATSUOKA:
> Graphics tool kit: qt and fltk
> plot (1:1, 'o', 'markersize', 24)
> print -depsc circle.eps
> plotted circle is regular decagon (ugly).
The code to draw the markers with OpenGL is in gl-render.cc
opengl_renderer::make_marker_list
case 'o':
{
double ang_step = M_PI / 5;
glBegin ((filled ? GL_POLYGON : GL_LINE_LOOP));
for (double ang = 0; ang < (2*M_PI); ang += ang_step)
glVertex2d (sz*cos (ang)/2, sz*sin (ang)/2);
glEnd ();
}
As you can see the decagon is hardcoded. AFAIK there is no "draw circle"
command in OpenGL so the only way to get a smoother circle would be to
increase the numer of segments.
-- Andy