Question

I’m using Linux and GLUT. I have a square as follows:

glVertex3f(-1.0, +1.0, 0.0); // top left glVertex3f(-1.0, -1.0, 0.0); // bottom left glVertex3f(+1.0, -1.0, 0.0); // bottom right glVertex3f(+1.0, +1.0, 0.0); // top right 

I guess I can’t use glutBitmapCharacter, since this is only ideal for 2D ortho.

Simple enough, I’d like to render ‘Hello world!’ anywhere on said square. Should I create a texture and then apply it to the vertices using glTexCoord2f?

Answer 1

The simplest way is to load a font map from a image, such as those generated by the bitmap font builder (I know it’s windows but I can’t find one for linux), eg:

The example is a 256×256 gif, though you may what to convert it to a png/tga/bmp. It’s full ASCII mapped gird, 16×16 characters. Load the texture and use glTexCoord2f to line it up on your quad, and you should be good to go.

Here’s an example using a bitmap of the above:

unsigned texture = 0;  void LoadTexture() {     // load 24-bit bitmap texture     unsigned offset, width, height, size;     char *buffer;     FILE *file = fopen('text.bmp', 'rb');     if (file == NULL)         return;     fseek(file, 10, SEEK_SET);     fread(&offset, 4, 1, file);     fseek(file, 18, SEEK_SET);     fread(&width, 1, 4, file);     fread(&height, 1, 4, file);      size = width * height * 3;      buffer = new char[size];      fseek(file, offset, SEEK_SET);     fread(buffer, 1, size, file);      glEnable(GL_TEXTURE_2D);     glGenTextures(1, &texture);     glBindTexture(GL_TEXTURE_2D, texture);     glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);     glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);     glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, buffer);      fclose(file);     printf('Loaded\n'); }  void DrawCharacter(char c) {     int column = c % 16, row = c / 16;     float x, y, inc = 1.f / 16.f;     x = column * inc;     y = 1 - (row * inc) - inc;      glBegin(GL_QUADS);       glTexCoord2f( x,       y);       glVertex3f( 0.f, 0.f, 0.f);       glTexCoord2f( x,       y + inc); glVertex3f( 0.f, 1.f, 0.f);       glTexCoord2f( x + inc, y + inc); glVertex3f( 1.f, 1.f, 0.f);       glTexCoord2f( x + inc, y);       glVertex3f( 1.f, 0.f, 0.f);     glEnd(); }