Re: Text properties and FTGL

[John Swensen]

On Oct 31, 2008, at 10:21 PM, Bill Denney wrote:

> John Swensen wrote:
> > Thanks for pointing these out.  I don't know what they are not doing
> > in mathTeX that I must be doing in my system calls, but mathTeX is
> > significantly faster.  Since it is GPL and Octave is GPL I will
> > probably actually compile this into my Octave tests and render
> > straight to the openGL texture, rather than have it render to a file
> > and then read it back in.  I think a time of ~0.1 seconds per LaTeX
> > string and appropriate caching of the results is acceptable.
>
> Just a thought, but could you render each result on a different page  
> in
> the LaTeX output and make it just ~0.1 sec total instead?
>
> Have a good day,
>
> Bill

I just tested that and you are exactly right.  Until I had more than  
100 equations (each on a different page), the time did not go over  
~0.15 seconds.  Even at 400 equations it was only 0.3 seconds.  I also  
found out that with the poppler library I can do all the cropping and  
such, so there is no need to call the pdfcrop script at all.  This  
will probably work after all.

As a side note, I did look at the mimeTeX program that was mentioned  
in this thread.  It is not a full TeX/LaTex interpreter, but has  
almost all basic symbols and constructs.  It essentially generates  
bitmaps from a set of fonts described in one of the header files.  It  
looks like the author rendered all of the characters, accents, etc for  
a specific size from Latex  to a bitmap and then converted those  
bitmaps into C arrays and put them all into a header file.  This  
method would scale horribly, but the nice thing is that it is wholly  
contained in about 2 header files and one source file.  For the "LaTeX- 
free" Octave, maybe it makes sense to borrow from his (it is GPL also)  
and instead of a single header file of font bitmaps, simply include  
every 2 points from 8 to 20.  This would look OK and we can still have  
the runtime check for the full version of LaTeX.

So here is my proposed work plan for the next little while:

1) Get the most basic and easiest thing working: pdflatex+poppler to  
render text to the OpenGL renderer
2) Get other cases working where pdflatex is not present, but LaTeX  
is:  latex+dvipdf+poppler to render text to the OpenGL renderer (as a  
non-related side note, does anyone have a two sentence explanation as  
to why pdflatex renders documents so much better than latex+dvipdf?)
3) Add in the non-LaTeX based converter from LaTeX to bitmap (low  
priority)

I now have an OpenGL question about textures.  Poppler converts the  
PDF into a buffer of the form numpixels * (RGBA), where the PDF has  
been scaled and the DPI chosen before this conversion to pixels takes  
place, so things are anti-aliased and everything is beautiful.  My  
problem is that it renders a white background and that keeps showing  
up when I render the texture to opengl with  
glBegin(GL_QUADS);...glEnd();.  With other programs I have used  
before, I should either be able to (1) just set the color I want to be  
the alpha color or (2) go through and set the value in the alpha  
channel for each of the pixels where I want it to be transparent to 1  
(or 255).  I don't know how to do (1) with OpenGL and when I try to do  
(2) nothing happens.

John Swensen