I've got this problem where a simple cube will overlap itself... but depth drawing appears to work and not overlap other cubes.
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It's a super weird effect. I kept thinking my cube drawing function was missing a face, or the face was positioned in the center but it's not.
Here's some code... I tried to remove non-graphics related stuff.
1
2int initialize()
3 {
4 if (!al_init())
5 {
6 printf("Could not init Allegro.\n");
7 return 1;
8 }
9
10 al_init_primitives_addon();
11 al_install_mouse();
12 al_install_keyboard();
13 al_init_image_addon();
14 al_init_font_addon();
15
16 al_set_new_display_flags(ALLEGRO_WINDOWED);
17 al_set_new_display_flags(ALLEGRO_OPENGL);
18 display = al_create_display(SCREEN_WIDTH, SCREEN_HEIGHT);
19
20 if (!display)
21 {
22 printf("Error creating display\n");
23 return 1;
24 }
25
26 al_set_target_bitmap(al_get_backbuffer(display));
27 al_clear_to_color(al_map_rgb(0,0,0));
28
29 glEnable(GL_DEPTH_TEST);
30 glDepthFunc( GL_LEQUAL );
31 glHint( GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST );
32
33 return 0;
34 }
35
36void set_camera_position()
37 {
38 glMatrixMode(GL_PROJECTION);
39 glLoadIdentity();
40 glFrustum(-1.0, 1.0, -1.0, 1.0, 1.0, 40.0);
41 glTranslatef(camera.x, camera.y, -camera.dist);
42 glRotatef(camera.xangle, 1, 0, 0);
43 glRotatef(camera.yangle, 0, 1, 0);
44 glRotatef(camera.zangle, 0, 0, 1);
45 glMatrixMode(GL_MODELVIEW);
46 }
47
48
49void draw_cube()
50 {
51
52 glBegin(GL_QUADS);
53
54 // BOTTOM
55 glColor3f( 0.0, 1.0, 1.0 );
56 glVertex3f( 0.5, -0.5, -0.5 );
57 glVertex3f( 0.5, 0.5, -0.5 );
58 glVertex3f( -0.5, 0.5, -0.5 );
59 glVertex3f( -0.5, -0.5, -0.5 );
60
61 // White side - TOP
62 glColor3f( 1.0, 1.0, 1.0 );
63 glVertex3f( 0.5, -0.5, 0.5 );
64 glVertex3f( 0.5, 0.5, 0.5 );
65 glVertex3f( -0.5, 0.5, 0.5);
66 glVertex3f( -0.5, -0.5, 0.5 );
67
68 // Purple side - RIGHT
69 glColor3f( 1.0, 0.0, 1.0 );
70 glVertex3f( 0.5, -0.5, -0.5 );
71 glVertex3f( 0.5, 0.5, -0.5 );
72 glVertex3f( 0.5, 0.5, 0.5 );
73 glVertex3f( 0.5, -0.5, 0.5 );
74
75 // Green side - LEFT
76 glColor3f( 0.0, 1.0, 0.0 );
77 glVertex3f( -0.5, -0.5, 0.5 );
78 glVertex3f( -0.5, 0.5, 0.5 );
79 glVertex3f( -0.5, 0.5, -0.5 );
80 glVertex3f( -0.5, -0.5, -0.5 );
81
82 // Blue side - BACK
83 glColor3f( 0.0, 0.0, 1.0 );
84 glVertex3f( 0.5, 0.5, 0.5 );
85 glVertex3f( 0.5, 0.5, -0.5 );
86 glVertex3f( -0.5, 0.5, -0.5 );
87 glVertex3f( -0.5, 0.5, 0.5 );
88
89 // Red side - FRONT
90 glColor3f( 1.0, 0.0, 0.0 );
91 glVertex3f( 0.5, -0.5, -0.5 );
92 glVertex3f( 0.5, -0.5, 0.5 );
93 glVertex3f( -0.5, -0.5, 0.5 );
94 glVertex3f( -0.5, -0.5, -0.5 );
95 glEnd();
96 }
97
98void draw_cube_at(double x, double y, double z)
99 {
100 glPushMatrix();
101 glTranslatef(-2.5 + x, 0.0 +y , 0.0 + z);
102 draw_cube();
103 glPopMatrix();
104 }
Most of this stuff is derived from the opengl.cpp and opengl2.cpp Allegro examples.
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