Text writing and ortho

OpenGL OpenGL: Basic Coding
1

I tried to display texture mapped fonts. I read at the NeHe site, that I shouldn’t use Ortho, because it is ugly. In my case, I have to use it. And it’s faster to set the screen coordinates.
I used the code below:

glMatrixMode( GL_MODELVIEW );
glPushMatrix();
glDisable(GL_LIGHTING);
/***** gluOrtho2D(0,800, 600,0);*******/
/***** glRasterPos2i(50,50); **********/
glPushAttrib(GL_LIST_BIT);
glListBase(base);
glCallLists(6, GL_UNSIGNED_BYTE, “Hello.”);
glPopAttrib();

glPopMatrix();
SwapBuffers(DCvalue);

This code works perfectly, but if I enable the glOrtho and the rasterpos lines, I don’t get anything written on the screen.
What is wrong here??? Pls help

2

You put it into the wrong matrix. Try this:

glMatrixMode(GL_MODELVIEW);
glPushMatrix(); // GL_MODELVIEW
glLoadIdentity();
glMatrixMode(GL_PROJECTION);
glPushMatrix(); // GL_PROJECTION
glLoadIdentity();
gluOrtho2D(0.0, 800.0, 600.0, 0.0);
glPushAttrib(GL_LIST_BIT | GL_LIGHTING_BIT);
glDisable(GL_LIGHTING);
glListBase(base);
glColor3f(1.0, 1.0, 1.0); // Your font color when using bitmaps.
glRasterPos2i(50, 50);
glCallLists(6, GL_UNSIGNED_BYTE, "Hello.");
glPopAttrib(); // list base and lighting state restored
glPopMatrix(); // GL_PROJECTION
glMatrixMode(GL_MODELVIEW);
glPopMatrix(); // GL_MODELVIEW
SwapBuffers(DCvalue);

The code above should work nicely with wglUseFontBitmaps. With a do-it-yourself texture font, what did you compile into the display lists which works with glRasterPos? (Means, it’s not useful for a font texture.)
If you use textured quads per letter, switch the GL_MODELVIEW to be inside in my code, so that possible glTranslate calls you have per letter affect that right matrix.
If this doesn’t help, set your glClearColor to a weird color.
Check your font texture environment (e.g. GL_REPLACE instead of GL_MODULATE).

3

Strange. I don’t see anything…
Maybe the error is in the previous lines? I pasted your code directly into mine, overwriting everything.
Here’s what comes before your code:

HFONT fontol = CreateFont(40, 8, 0, 0,
FW_DONTCARE, 0, 0, 0,
ANSI_CHARSET,
OUT_OUTLINE_PRECIS,
CLIP_DEFAULT_PRECIS,
DEFAULT_QUALITY, FF_DONTCARE|DEFAULT_PITCH,
“Arial”);
SelectObject(DCvalue, fontol);

BOOL font = wglUseFontOutlines(DCvalue, 0, 255, base, 0.1f, 0.2f,
WGL_FONT_POLYGONS, agmf);

glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);

load_image(“d:\10_1.bmp”);

glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, backgr);

glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_OBJECT_LINEAR);
Object
glTexGeni(GL_T, GL_TEXTURE_GEN_MODE, GL_OBJECT_LINEAR);
glEnable(GL_TEXTURE_GEN_S);
glEnable(GL_TEXTURE_GEN_T);

glListBase(base);

Still nothing… I don’t understand. Your code must be correct.

4

Does it work without the texture?
Wait, you said that code worked before, so what was your matrix setup then?
Maybe it’s so tiny that there is only a single point.
With wglUseFontOutlines you should probably move the modelview inside like this, as I don’t know how the display lists advance the position depending on the glyph widths:

 
glMatrixMode(GL_PROJECTION);
glPushMatrix(); // GL_PROJECTION
glLoadIdentity();
gluOrtho2D(0.0, 800.0, 0.0, 600.0); // Let's order it the OpenGL way for debugging.

glMatrixMode(GL_MODELVIEW);
glPushMatrix();// GL_MODELVIEW
glLoadIdentity();

glPushAttrib(GL_LIST_BIT | GL_LIGHTING_BIT);
glDisable(GL_LIGHTING);
glListBase(base);
glColor3f(1.0, 1.0, 1.0); // Your font color when using bitmaps.
glRasterPos2i(50, 50);
glCallLists(6, GL_UNSIGNED_BYTE, "Hello.");
glPopAttrib(); // list base and lighting state restored

glMatrixMode(GL_PROJECTION);
glPopMatrix(); // GL_PROJECTION

glMatrixMode(GL_MODELVIEW);
glPopMatrix(); // GL_MODELVIEW

SwapBuffers(DCvalue);

If this gets you a tiny point in the bottom left corner, try gluOrtho2D(0.0, 8.0, 0.0, 6.0);
Bigger now?

5

The whole code works OK when I remove the glOrtho line. The letters appear at position 0,0. This is normal.
If I leave Ortho, I see a black screen.

The bitmap i use is a 512x512 bmp. It is loaded correctly, as the result is fine (without Ortho).

I think i will use another way to display the text: 0,0 is the center of the screen(400,300). -1,-1 will be 0,0, etc. Maybe. A bit lame thing when you can have ortho…

Thank you for the help. If you want, you can continue trying, but I don’t want to ask more of your time.
This thing remains a mistery to me. I used Ortho many times and it only failed once: with fonts…

6

Got it. I missed your last line. :smiley:
But now, I got the text in the botton left corner.

Thank you for the help.