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Text properties and FTGL
From: |
John Swensen |
Subject: |
Text properties and FTGL |
Date: |
Sat, 25 Oct 2008 22:06:01 -0400 |
So I have been messing around with FTGL today and it looks quite easy
to use. I was able to get the xlabel, ylabel, and zlabel working
(kindof!) and have a few questions and comments.
Comments
FTGL is very easy to use. I used their simple little singleton class
example from the web page for getting fonts back to octave and then
did a simple render of the label property in label sections of the
opengl_renderer::draw() function in gl-render.cc. I used the
FTTextureFont, since it appears that it is the only one that is anti-
aliased and allows difference colors.
Problems
1) At first, I was trying the following command to draw a sample plot
and xlabel:
t=-pi:0.1:pi; plot(t,sin(t),'ro','LineWidth',2);
xlabel('asdfASDFQWERqwerZXCVzxcvasdfASDF');
The text was showing up very, very large even for a fontsize of 12
points with a 72 points per inch resolution. When I tried to reduce
the fontsize down below a out 5, the text simply disappeared and even
at 6 it was huge. Not even the first letter 'a' was visible in its
entirety on the screen. I was quite confused.
Then, I tried the following command for plotting:
t = -100:100; plot(t,100*sin(t),'r');
xlabel('asdfASDFqwerQWERzxcvZXCV');
With this command, the text looked much more reasonably sized so I cam
to the conclusion that the OpenGL render method is really plotting at
the size of the signal values, rather than scaling up to some sort of
default size. I think we need to scale up the plots so that 12 points
in text with a 72 ppi screen is really 12 points.
(BIG CAVEAT: I know next to nothing about OpenGL, so I am not a lot of
help when having to do low level OpenGL stuff.)
Also, I searched around on the internet a bit about fonts in OpenGL
and it seems that FTGL using Freetype is in fact the "best" option out
there. However, it seemed that there is a general consensus that
OpenGL doesn't do small font sizes well. Things start to get fuzzy
and then disappear (just like I was seeing when I thought just
shrinking the fontsize property would fix things). Since I don't know
OpenGL I can' t appreciate why this happens, but I think that scaling
the plots to match the text size should work, since I don't know of
many situations where a font size smaller than 6 pt is necessary anyway.
I guess I don't think a patch would be in order right now since the
labels aren't very useful when their size changes relative to the plot
at hand.
2) The position property is not working for the xlabel position
property. I guess maybe this is expected behavior. I don't know if
Matlab allows you to update the label positions after they have been
drawn or not.
I'll let you know when I have more figured out.
John Swensen
- Text properties and FTGL,
John Swensen <=
- Re: Text properties and FTGL, Shai Ayal, 2008/10/26
- Re: Text properties and FTGL, John Swensen, 2008/10/28
- Re: Text properties and FTGL, John W. Eaton, 2008/10/28
- Re: Text properties and FTGL, Shai Ayal, 2008/10/28
- Re: Text properties and FTGL, John W. Eaton, 2008/10/28
- Re: Text properties and FTGL, Shai Ayal, 2008/10/28
- Re: Text properties and FTGL, John W. Eaton, 2008/10/28
- Re: Text properties and FTGL, Thomas Weber, 2008/10/28
- Re: Text properties and FTGL, Jordi GutiƩrrez Hermoso, 2008/10/28
- Re: Text properties and FTGL, John Swensen, 2008/10/28