[OpenGL] Draw in 2d after drawing in 3d http://www.allegro.cc/forums/view/586476 Allegro.cc Forum Thread matthew@allegro.cc (Matthew Leverton) Mon, 17 Jul 2006 04:54:09 +0000

What I'm wondering, is let's say the 3d scene is drawn. Is there a way to then draw in 2d flat on the screen? For example, if I wanted to have a HUD or mouse cursor over the scene, could I just draw those straight to the screen flat?

I know I could figure out all the business as to where those things would be in 3d space and constantly move them with the camera, but it'd be a lot easier if there was just a way to draw it 2d after the 3d was done :)

]]> no-reply@allegro.cc (BrknPhoenix) Fri, 14 Jul 2006 23:37:37 +0000

After drawing the 3d scene, simply reset the modelview and projection matrix, then set an ortho mode (glOrtho).

1glMatrixMode(GL_PROJECTION);
2glLoadIdentity();
3gluPerspective(45.0f, float(SCREEN_W)/SCREEN_H, 1.0f, 10000.0f);
4glMatrixMode(GL_MODELVIEW);
5 
6while(playing)
7{
8 glLoadIdentity();
9 draw_3d_stuff_here();
10 
11 glMatrixMode(GL_PROJECTION);
12 glPushMatrix();
13 glLoadIdentity();
14 glOrtho(0, SCREEN_W, SCREEN_H, 0, -1, 1);
15 glMatrixMode(GL_MODELVIEW);
16 
17 draw_2d_stuff_here();
18 
19 glMatrixMode(GL_PROJECTION);
20 glPopMatrix();
21 glMatrixMode(GL_MODELVIEW);
22}

]]> no-reply@allegro.cc (Kitty Cat) Sat, 15 Jul 2006 00:27:47 +0000

It doesn't appear to be working. My mouse cursor, which worked in 2D, has stopped showing up when 3D was added. I put in the code that you suggested and nothing happened differently.

]]> no-reply@allegro.cc (BrknPhoenix) Mon, 17 Jul 2006 04:23:20 +0000

Show the code. Can't tell what's wrong without seeing what you're doing. :)

]]> no-reply@allegro.cc (Kitty Cat) Mon, 17 Jul 2006 04:38:36 +0000

Initial setup

    else if (projection_type == FRUSTUM)
    {
        glMatrixMode(GL_PROJECTION);
        glEnable(GL_TEXTURE_2D);
        glEnable(GL_DEPTH_TEST);        
        glLoadIdentity();
       gluPerspective(45.0f, (GLfloat)SCREEN_WIDTH / (GLfloat)SCREEN_HEIGHT, 1.0f, 1000.0f);         
        glViewport(0, 0, SCREEN_WIDTH, SCREEN_HEIGHT);           
        glClearColor(0.0f, 0.0f, 0.0f, 0.0f);        
    }
}

This is the drawing function:

void objGfx::DoDraw(int s)
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);            
    
    Do3D(s);
    
    Do2D(s);    
    
    allegro_gl_flip();
}

3D function 

void objGfx::Do3D(int s)
{
    switch (s)
    {
        case SCENE_TITLE:
            glMatrixMode(GL_MODELVIEW);
            glLoadIdentity();                                                                                      
            break;
        case SCENE_NONE:
            glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
        default:
            break;            
    }    
}

2D Function

1void objGfx::Do2D(int s)
2{
3 glMatrixMode(GL_PROJECTION);
4 glPushMatrix();
5 glLoadIdentity();
6 glOrtho(0, SCREEN_WIDTH, SCREEN_HEIGHT, 0, -1, 1);
7 glMatrixMode(GL_MODELVIEW);
8
9 switch (s)
10 {
11 case SCENE_TITLE:
12 break;
13 case SCENE_NONE:
14 default:
15 break;
16 }
17
18 if (Mouse->Visible())
19 {
20 Draw->Sprite(Mouse->TextureSprite(), Mouse->TextureMask(),
21 Mouse->X(), Mouse->Y(),
22 Mouse->X() + Mouse->CursorWidth(),
23 Mouse->Y() + Mouse->CursorHeight());
24 }
25
26 if (DEBUG)
27 {
28 Debug->Output();
29 }
30
31 glMatrixMode(GL_PROJECTION);
32 glPopMatrix();
33 glMatrixMode(GL_MODELVIEW);
34}

]]> no-reply@allegro.cc (BrknPhoenix) Mon, 17 Jul 2006 04:46:47 +0000

What are the Mouse and Draw objects? At a glance, everything you pasted looks alright, so the problem is somewhere else.

]]> no-reply@allegro.cc (Kitty Cat) Mon, 17 Jul 2006 04:51:15 +0000

edit: I figured out the problem actually does have to do with how the mouse is being drawn, but I don't know what. I've since moved on to an attempt at a different solution.

Draw->Sprite

1void objDraw::Sprite(GLuint sprite, GLuint mask, int x1, int y1, int x2, int y2)
2{
3 glEnable(GL_TEXTURE_2D);
4 glEnable(GL_BLEND);
5 glBlendFunc(GL_DST_COLOR, GL_ZERO);
6
7 glBindTexture(GL_TEXTURE_2D, mask);
8
9 glBegin(GL_QUADS);
10 glTexCoord3f(0, 0, 0); glVertex3f(x1, y2, 0);
11 glTexCoord3f(1, 0, 0); glVertex3f(x2, y2, 0);
12 glTexCoord3f(1, 1, 0); glVertex3f(x2, y1, 0);
13 glTexCoord3f(0, 1, 0); glVertex3f(x1, y1, 0);
14 glEnd();
15 
16 glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
17
18 glBindTexture(GL_TEXTURE_2D, sprite);
19 glBlendFunc(GL_ONE, GL_ONE);
20
21 glBegin(GL_QUADS);
22 glTexCoord3f(0, 0, 0); glVertex3f(x1, y2, 0);
23 glTexCoord3f(1, 0, 0); glVertex3f(x2, y2, 0);
24 glTexCoord3f(1, 1, 0); glVertex3f(x2, y1, 0);
25 glTexCoord3f(0, 1, 0); glVertex3f(x1, y1, 0);
26 glEnd();
27}

Mouse everything

1#include <allegro.h>
2#include <alleggl.h>
3 
4#include "mouse.h"
5 
6#include "defines.h"
7#include "globals.h"
8 
9objMouse::objMouse()
10{
11 visible = false;
12}
13 
14objMouse::~objMouse()
15{
16 destroy_bitmap(m_sprite);
17 destroy_bitmap(m_mask);
18}
19 
20int objMouse::X()
21{
22 return mouse_x;
23}
24 
25int objMouse::Y()
26{
27 return mouse_y;
28}
29 
30int objMouse::Z()
31{
32 return mouse_z;
33}
34 
35int objMouse::LeftButton()
36{
37 if (mouse_b & 1)
38 {
39 return true;
40 }
41 else
42 {
43 return false;
44 }
45}
46 
47int objMouse::RightButton()
48{
49 if (mouse_b & 2)
50 {
51 return true;
52 }
53 else
54 {
55 return false;
56 }
57}
58 
59int objMouse::MiddleButton()
60{
61 if (mouse_b & 4)
62 {
63 return true;
64 }
65 else
66 {
67 return false;
68 }
69}
70 
71BITMAP* objMouse::CursorSprite()
72{
73 return m_sprite;
74}
75 
76BITMAP* objMouse::CursorMask()
77{
78 return m_mask;
79}
80 
81bool objMouse::Visible()
82{
83 return visible;
84}
85 
86int objMouse::CursorWidth()
87{
88 return m_sprite->w;
89}
90 
91int objMouse::CursorHeight()
92{
93 return m_sprite->h;
94}
95 
96GLuint objMouse::TextureSprite()
97{
98 return texSprite;
99}
100 
101GLuint objMouse::TextureMask()
102{
103 return texMask;
104}
105 
106void objMouse::SetCursorSprite(const char* filename)
107{
108 m_sprite = load_bitmap(filename, NULL);
109 texSprite = allegro_gl_make_texture(m_sprite);
110}
111 
112void objMouse::SetCursorMask(const char* filename)
113{
114 m_mask = load_bitmap(filename, NULL);
115 texMask = allegro_gl_make_texture(m_mask);
116}
117 
118void objMouse::Show()
119{
120 visible = true;
121}
122 
123void objMouse::Scare()
124{
125 visible = false;
126}
127 
128void objMouse::Draw()
129{
130 allegro_gl_set_allegro_mode();
131 
132 draw_sprite(screen, m_sprite, mouse_x, mouse_y);
133
134 allegro_gl_unset_allegro_mode();
135}

Note the Mouse->Draw function isn't actually used... I just forgot to take it out, hehe

]]> no-reply@allegro.cc (BrknPhoenix) Mon, 17 Jul 2006 04:54:09 +0000