CODEWITHSUNDEEP
openglglut
HiMing
HiMing

Reputation: 361

I have a problem about opengl glut glutStrokeCharacter, the code did not work?

I write a opengl code on ubuntu. I want to draw a text on the screen, but the output() function seems not work. Can you tell me why?

http://pyopengl.sourceforge.net/documentation/manual/glutStrokeCharacter.3GLUT.html

void output(GLfloat x, GLfloat y, char *text)
{
    char *p;

    glPushMatrix();
    glTranslatef(x, y, 0);
    for (p = text; *p; p++)
    glutStrokeCharacter(GLUT_STROKE_ROMAN, *p);
    glPopMatrix();
}

void myDraw(void)
{
    glClear(GL_COLOR_BUFFER_BIT);

    glColor3f(1.0f,1.0f,0.0f);
    glBegin(GL_POLYGON);
    glVertex2f(-0.8,0.8);
    glVertex2f(-0.2,0.8);
    glVertex2f(-0.2,0.5);
    glVertex2f(-0.8,0.5);
    glEnd();
    glFlush();

    glColor3f(1.0f,0.0f,0.0f);
    output(-0.8,0.8,"hello");     // why not show text

    glFlush();
}

int main(int argc,char ** argv)
{
    printf("init\n");
    glutInit(&argc,argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(SCALE,SCALE);
    glutInitWindowPosition(100,100);

    glutCreateWindow("MENU");

    glutDisplayFunc(myDraw);

    glutMouseFunc(processMouse);

    glutMainLoop();
    return 0;
}

Upvotes: 4

Views: 6977

Answers (1)

genpfault
genpfault

Reputation: 52083

Try scaling the text down a bit first:

#include <GL/glut.h>

double aspect_ratio = 0;
void reshape(int w, int h)
{
    aspect_ratio = (double)w / (double)h;
    glViewport(0, 0, w, h);
}

void output(GLfloat x, GLfloat y, char* text)
{
    glPushMatrix();
    glTranslatef(x, y, 0);
    glScalef(1/152.38, 1/152.38, 1/152.38);
    for( char* p = text; *p; p++)
    {
        glutStrokeCharacter(GLUT_STROKE_ROMAN, *p);
    }
    glPopMatrix();
}

void display(void)
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(-10*aspect_ratio, 10*aspect_ratio, -10, 10, -1, 1);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glColor3ub(255,0,0);
    output(0,0,"hello");

    glutSwapBuffers();
}

int main(int argc, char **argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGBA | GLUT_DEPTH | GLUT_DOUBLE);

    glutInitWindowSize(640,480);
    glutCreateWindow("Text");

    glutDisplayFunc(display);
    glutReshapeFunc(reshape);
    glutMainLoop();
    return 0;
}

If you read the documentation you provided you'll find that GLUT_STROKE_ROMAN is rather large by default, around 152 units tall.

If I recall correctly the default projection and modelview matrices that you're depending on give you a view area that only covers about (-1,-1) to (1,1).

Upvotes: 4

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