Sharpgl can see a line parallel to the Z axis

Asked Apr 10 '19 at 17:02

Active Apr 10 '19 at 17:34

Viewed 98 times

I drew a line parallel to the Z axis in sharpgl. I set the camera above the Z axis, so I thought I would see 1 point, but I don't see it. Later I want to draw a large number of these lines side by side, now I'm trying on one.

Camera settings:

gl.Ortho (0, 1595, 0, 1000, -30, 80);

gl.LookAt(0.0f, 0.0f, 90.0f, 0.0f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f);

Line Drawing:

gl.LineWidth (100.0f);
gl.Begin (OpenGL.GL_LINES);
gl.Color (0, 0, 0);
gl.Vertex (600, 600, 30);
gl.Vertex (600, 600, 50);
gl.End ();
gl.Flush ();

When I draw a line at a different angle, you can see it:

gl.Vertex (180, 15, 20);
gl.Vertex (800, 800, 20);

When I draw only a point, I also see it:

gl.PointSize (100.0f);
gl.Begin (OpenGL.GL_POINTS);
gl.Color (0, 0, 0);
gl.Vertex (800, 800, 20);
gl.End ();

I need to see the line. Do I need to add a point to the beginning and end of a line, or is it just something to set the line to be visible?

edited Apr 10 '19 at 17:34

Nicol Bolas

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asked Apr 10 '19 at 17:02

jklasdf

1

How exactly do you expect to 'see the line'? If it's parallel to the z-axis in orthographic projection then the start and end points of the line coincide on the screen, so it has zero length -- thus nothing is drawn. – Yakov Galka Apr 10 '19 at 17:34
I want to see 1 point. – jklasdf Apr 10 '19 at 17:39
Then you'll need to draw it with `GL_POINTS` indeed. OpenGL won't do that automatically simply because it's not how it rasterizes lines. – Yakov Galka Apr 10 '19 at 17:40
Thanks for advice. – jklasdf Apr 10 '19 at 17:45

Sharpgl can see a line parallel to the Z axis

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