Displaying fixed location 2D text in a 3D OpenGL world using GLUT

Question

I have an OpenGL project which uses GLUT (not freeglut) wherein I would like to display 2D text on the viewport at a fixed location. The rest of my

Answer 1

As I said, the code you posted works perfectly fine. Here's the code I used to test it:

#ifdef __APPLE__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif

#include "GL/glu.h"
//glm not required
//#include <glm.hpp>
//#include <gtc/matrix_transform.hpp>
#include <string>

int win_width = 500, win_height = 500;

void renderScene(void) {

    static float dis=0, ddis=0, elev=0, delev=0, azim=0, dazim=0;

    azim += 0.5f;
    if (azim >= 360.0f){
        azim -= 360.0f;
    }

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glLoadIdentity();
    glTranslatef(0.0f, 0.0f, -(dis + ddis));
    glRotated(elev + delev, 1.0, 0.0, 0.0);
    glRotated(azim + dazim, 0.0, 1.0, 0.0);
    glScalef(2.0f,2.0f,2.0f);

    glBegin(GL_TRIANGLES);
        glColor3f(1.0f, 1.0f, 0.0f);
        glVertex3f(-0.5f, -0.5f, 0.0f);
        glColor3f(0.0f, 1.0f, 0.0f);
        glVertex3f(0.5f, 0.0f, 0.0f);
        glColor3f(0.0f, 0.0f, 1.0f);
        glVertex3f(0.0f, 0.5f, 0.0f);
    glEnd();


    glMatrixMode(GL_PROJECTION);
    glPushMatrix();
    glLoadIdentity();
    //I like to use glm because glu is deprecated
    //glm::mat4 orth= glm::ortho(0.0f, (float)win_width, 0.0f, (float)win_height);
    //glMultMatrixf(&(orth[0][0]));
    gluOrtho2D(0.0, win_width, 0.0, win_height);
    glMatrixMode(GL_MODELVIEW);
    glPushMatrix();
    glLoadIdentity();
    glColor3f(1.0f, 0.0f, 0.0f);//needs to be called before RasterPos
    glRasterPos2i(10, 10);
    std::string s = "Some text";
    void * font = GLUT_BITMAP_9_BY_15;

    for (std::string::iterator i = s.begin(); i != s.end(); ++i)
    {
        char c = *i;
        //this does nothing, color is fixed for Bitmaps when calling glRasterPos
        //glColor3f(1.0, 0.0, 1.0); 
        glutBitmapCharacter(font, c);
    }
    glMatrixMode(GL_MODELVIEW);
    glPopMatrix();
    glMatrixMode(GL_PROJECTION);
    glPopMatrix();
    glEnable(GL_TEXTURE_2D);

    glutSwapBuffers();
    glutPostRedisplay();
}

int main(int argc, char **argv) {

    // init GLUT and create Window
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
    glutInitWindowPosition(100, 100);
    glutInitWindowSize(win_width, win_height);
    glutCreateWindow("GLUT Test");

    // register callbacks
    glutDisplayFunc(renderScene);

    // enter GLUT event processing cycle
    glutMainLoop();

    return 1;
}

The usual disclaimers about deprecated fixed function pipeline and others apply.

Answer 2

I ran into this same problem using glut to create a model of the solar system. Here's how I solved it: (using your code from above)

glDisable(GL_TEXTURE_2D); //added this
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
gluOrtho2D(0.0, win_width, 0.0, win_height);
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
glLoadIdentity();
glRasterPos2i(10, 10);
string s = "Some text";
void * font = GLUT_BITMAP_9_BY_15;
for (string::iterator i = s.begin(); i != s.end(); ++i)
{
  char c = *i;
  glColor3d(1.0, 0.0, 0.0);
  glutBitmapCharacter(font, c);
}
glMatrixMode(GL_PROJECTION); //swapped this with...
glPopMatrix();
glMatrixMode(GL_MODELVIEW); //...this
glPopMatrix();
//added this
glEnable(GL_TEXTURE_2D);

You'll note i switched glMatrixMode(GL_PROJECTION); and glMatrixMode(GL_MODELVIEW); near the end. I decided to do this because of this website. I also has to surround the code section with glDisable(GL_TEXTURE_2D) and glEnable(GL_TEXTURE_2D).

Hope that helps- I worked for me. My solar system uses classes to perform all of this, I'd be happy to share more details upon request.

Answer 3

There is a tricky way to solve your problem.

Please write a code before you call a function or what ever it is as written below:

glutBitmaCharacter(font, ' ');// 

Does it....! And it should work...