[OpenGL] Draw in 2d after drawing in 3d

[OpenGL] Draw in 2d after drawing in 3d

BrknPhoenix

Member #7,304

June 2006

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

Kitty Cat

Member #2,815

October 2002

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}

--
"Do not meddle in the affairs of cats, for they are subtle and will pee on your computer." -- Bruce Graham

BrknPhoenix

Member #7,304

June 2006

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.

Kitty Cat

Member #2,815

October 2002

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

--
"Do not meddle in the affairs of cats, for they are subtle and will pee on your computer." -- Bruce Graham

BrknPhoenix

Member #7,304

June 2006

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{
  glMatrixMode(GL_PROJECTION);
  glPushMatrix();
  glLoadIdentity();
  glOrtho(0, SCREEN_WIDTH, SCREEN_HEIGHT, 0, -1, 1);
  glMatrixMode(GL_MODELVIEW);
  
  switch (s)
  {
      case SCENE_TITLE:
          break;
      case SCENE_NONE:
      default:
          break;
  }
  
  if (Mouse->Visible())
  {
      Draw->Sprite(Mouse->TextureSprite(), Mouse->TextureMask(),
                   Mouse->X(), Mouse->Y(),
                   Mouse->X() + Mouse->CursorWidth(),
                   Mouse->Y() + Mouse->CursorHeight());
  }
  
  if (DEBUG)
  {
      Debug->Output();
  }
  
  glMatrixMode(GL_PROJECTION);
  glPopMatrix();
  glMatrixMode(GL_MODELVIEW);    
34}

Kitty Cat

Member #2,815

October 2002

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

--
"Do not meddle in the affairs of cats, for they are subtle and will pee on your computer." -- Bruce Graham

BrknPhoenix

Member #7,304

June 2006

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{
  glEnable(GL_TEXTURE_2D);
  glEnable(GL_BLEND);
  glBlendFunc(GL_DST_COLOR, GL_ZERO);
  
  glBindTexture(GL_TEXTURE_2D, mask);
  
  glBegin(GL_QUADS);
      glTexCoord3f(0, 0, 0); glVertex3f(x1, y2, 0);
      glTexCoord3f(1, 0, 0); glVertex3f(x2, y2, 0);
      glTexCoord3f(1, 1, 0); glVertex3f(x2, y1, 0);
      glTexCoord3f(0, 1, 0); glVertex3f(x1, y1, 0);
  glEnd();
15 
  glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
  
  glBindTexture(GL_TEXTURE_2D, sprite);
  glBlendFunc(GL_ONE, GL_ONE);
  
  glBegin(GL_QUADS);
      glTexCoord3f(0, 0, 0); glVertex3f(x1, y2, 0);
      glTexCoord3f(1, 0, 0); glVertex3f(x2, y2, 0);
      glTexCoord3f(1, 1, 0); glVertex3f(x2, y1, 0);
      glTexCoord3f(0, 1, 0); glVertex3f(x1, y1, 0);        
  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