Problem: Allegro 5 & Opengl text drawing

no-reply@allegro.cc (Ghost101) — Wed, 02 May 2012 20:16:25 +0000

I have a problem with the allegro 5 and opengl combination

I want to use al_draw_textf for my fps counter. But it is always behind the perspective of opengl.

I use the functions in given sequence.
Can somebody please help me???

Code:

#SelectExpand
  1void Renderer::InitOpenGL()
  2    {
  3        glMatrixMode( GL_PROJECTION );
  4        glLoadIdentity();
  5        gluPerspective(45.0f,(GLfloat)WIDTH/(GLfloat)HEIGHT,0.1f,100.0f);
  6
  7        glMatrixMode(GL_MODELVIEW);
  8
  9        glEnable(GL_TEXTURE_2D);
 10        glEnable(GL_CULL_FACE);
 11        glEnable(GL_DEPTH_TEST);
 12        glShadeModel(GL_SMOOTH);
 13
 14        glDepthMask(GL_TRUE);
 15
 16        //glPolygonMode(GL_FRONT,GL_LINE);
 17        glPolygonMode(GL_FRONT,GL_FILL);
 18
 19        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 20    }

#SelectExpand
  1void Renderer::RenderBlock(float x, float y, float z, ALLEGRO_BITMAP* texture)
  {
      glPushMatrix();
      glTranslatef(x,y,z);
      glBindTexture(GL_TEXTURE_2D, al_get_opengl_texture(texture));
  6
      glBegin(GL_QUADS);
          // Front Face
          //glNormal3f( 0.0f, 0.0f, 1.0f);
          glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f,  1.0f);
          glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f,  1.0f);
          glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  1.0f,  1.0f);
          glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  1.0f,  1.0f);
          // Back Face
          //glNormal3f( 0.0f, 0.0f,-1.0f);
          glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f);
          glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f,  1.0f, -1.0f);
          glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f,  1.0f, -1.0f);
          glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f, -1.0f);
 20
          // All the other faces :D
      glEnd();
      glPopMatrix();
  }

#SelectExpand
  void Renderer::DrawFPS(ALLEGRO_FONT *font, int fps)
  {
      al_draw_textf(font, al_map_rgb(255, 255, 255), 5, 5, 0, "FPS: %i", fps);
  }

no-reply@allegro.cc (Elias) — Wed, 02 May 2012 21:06:24 +0000

Easiest way will be a brute foce method like:

// Just pseudocode, look up documentationf or all functions.

// right after al_create_display
glGetDoublev(GL_MODELVIEW_MATRIX, modelview)
glGetDoublev(GL_PROJECTION_MATRIX, projection)
glGetDoublev(GL_VIEWPORT, viewport)

// then later, before using Allegro functions
glViewport(viewport[0], viewport[1], viewport[2], viewport[3])
glMatrixMode(GL_PROJECTION)
gLoadMatrixd(projection)
glMatrixMode(GL_MODELVIEW)
gLoadMatrixd(modelview)

Basically, store whatever is the current transformation setup Allegro uses, then restore to that whenever using Allegro functions.

Alternatively you could check Allegro's source code and just set up the same matrices.

no-reply@allegro.cc (Ghost101) — Thu, 03 May 2012 22:39:21 +0000

ok thanks for the reaction but is there no way to not brute force it I wass thinking something like making one viewport transparant

or else is there a way to use text in opengl

no-reply@allegro.cc (Elias) — Thu, 03 May 2012 23:57:42 +0000

If you want the text to not be affected by the perspective transform, you need to disable that transform, no matter how you draw it.

no-reply@allegro.cc (SiegeLord) — Fri, 04 May 2012 00:00:58 +0000

Why not just push and pop the relevant matrices?

no-reply@allegro.cc (Ghost101) — Fri, 04 May 2012 13:32:34 +0000

ok that is something I am going to try