Allegro 5 OpenGL depth test problem

DQBO1998

I've been working on my first OpenGL project, I decided to implement it through Allegro 5.0.1 for the compiler MinGW 4.7.0. Currently I'm using TDM-GCC 4.7.1.
Well, the project consists on a simple 3D drawing library that is more like a wrapper for OpenGL.

The code I use to initialize OpenGL is.

flags = ALLEGRO_WINDOWED | ALLEGRO_OPENGL_3_0 | ALLEGRO_OPENGL; //allegro flags

Then to setup the projection matrix.

#SelectExpand
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  L3D_perspective(FOV, (GLfloat)screen_width/(GLfloat)screen_height, 1.0f, 100.0f);

And the last one is for renderin, right now it's called every time after or before drawing.

#SelectExpand
 1    glMatrixMode(GL_MODELVIEW);
 2    glLoadIdentity();

I created a function for testing, it shows a textured quad on the given position and also can handle some rotation.

#SelectExpand
  1void L3D_test_panel(GLfloat x, GLfloat y, GLfloat z, GLfloat x_angle, GLfloat y_angle, GLfloat z_angle, ALLEGRO_BITMAP *texture){
  2
  3    glPushMatrix();
  4
  5    glTranslatef(x, y, z);
  6    glRotatef(x_angle, 1, 0, 0);
  7    glRotatef(y_angle, 0, 1, 0);
  8    glRotatef(z_angle, 0, 0, 1);
  9    glBindTexture(GL_TEXTURE_2D, al_get_opengl_texture(texture));
 10    glEnable(GL_TEXTURE_2D);
 11
 12  /*  glClearDepth(1.0f);
 13    glDepthFunc(GL_LESS);
 14    glEnable(GL_DEPTH_TEST);*/
 15
 16    glBegin(GL_QUADS);
 17
 18    glTexCoord2f(0, 0); glVertex3f(-1, -1, -0);
 19    glTexCoord2f(1, 0); glVertex3f(+1, -1, -0);
 20    glTexCoord2f(1, 1); glVertex3f(+1, +1, -0);
 21    glTexCoord2f(0, 1); glVertex3f(-1, +1, -0);
 22
 23    glEnd();
 24
 25    glPopMatrix();
 26
 27}

The problem is that when I try to apply depth testing the polygons still overlap. I could you tell me the right way to set it?

Elias

The depth buffer has to be requested before creating a display. Simply put this before al_create_display:

al_set_new_display_option(ALLEGRO_DEPTH_SIZE, 16, ALLEGRO_SUGGEST);

DQBO1998

Thanks Elias, could you tell me when is it right to call glEnable(GL_DEPTH_TEST)? Because I want to know the "right" way.

Elias

Just once in the beginning. Unless you need to draw some things without depth test, then you will have to call glEnable/glDisable every time you need it enabled/disabled for drawing.

Thread #616355. Printed from Allegro.cc