CODEWITHSUNDEEP
c++visual-c++opengl2dglu
Peace Walker
Peace Walker

Reputation: 1

gluProject() setup in OpenGL VC++ beginner

I'm trying to convert 3D to 2D coordinates. and I understand I need to use gluProject(). But I'm facing troubles setting it up. I need to use Pixel coordinates

I need help in InitGL() how can I properly initialize it. also in DrawGLScene() how can use it? I need to keep the z variable for making layers so I don't want to disable it.

This is my code:

#ifdef WIN32
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#endif
#if defined(__APPLE__) && defined(__MACH__)
#include <OpenGL/gl.h>  // Header File For The OpenGL32 Library
#include <OpenGL/glu.h> // Header File For The GLu32 Library
#else
#include <GL/gl.h>  // Header File For The OpenGL32 Library
#include <GL/glu.h> // Header File For The GLu32 Library
#endif

#include "SDL.h"   // SDL library for managing input and window management (multipltform)
#include "SOIL.h"  // SOIL library for loading textures (multiplatform)

const int WINDOW_WIDTH = 640;
const int WINDOW_HEIGHT = 480;
const char* WINDOW_TITLE = "RB Game Engine";

float position=0;
GLuint  texture[1];  // number of texture = 1


/* A general OpenGL initialization function.  Sets all of the initial parameters. */
void InitGL(int Width, int Height)          // We call this right after our OpenGL window is created.
{
  LoadGLTextures();                                 // Jump To Texture Loading Routine ( NEW )
  glEnable(GL_TEXTURE_2D);                          // Enable Texture Mapping ( NEW )
  glViewport(0, 0, Width, Height);
  glClearColor(0.0f, 0.0f, 0.0f, 0.0f);     // This Will Clear The Background Color To Black
  glClearDepth(1.0);                // Enables Clearing Of The Depth Buffer
  glDepthFunc(GL_LESS);             // The Type Of Depth Test To Do
  glEnable(GL_DEPTH_TEST);          // Enables Depth Testing
  glShadeModel(GL_SMOOTH);          // Enables Smooth Color Shading

  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();             // Reset The Projection Matrix

  gluPerspective(45.0f,(GLfloat)Width/(GLfloat)Height,0.1f,100.0f); // Calculate The Aspect Ratio Of The Window

  glMatrixMode(GL_MODELVIEW);
}

/* The main drawing function. */
void DrawGLScene()
{
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);       // Clear The Screen And The Depth Buffer
  glLoadIdentity();             // Reset The View


  glTranslatef(0.0f,0.0f,-6.0f);                // Move Right 3 Units
  glBindTexture(GL_TEXTURE_2D, texture[0]); 
  // draw a square (quadrilateral)
  glBegin(GL_QUADS);                // start drawing a polygon (4 sided)
        glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f+position, -1.0f,  1.0f);
        glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f+position, -1.0f,  1.0f);
        glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f+position,  1.0f,  1.0f);
        glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f+position,  1.0f,  1.0f);
  glEnd();                  // done with the polygon



  // swap buffers to display, since we're double buffered.
  SDL_GL_SwapBuffers();
}

Upvotes: 0

Views: 2693

Answers (1)

Niels Kooiman
Niels Kooiman

Reputation: 111

You can use the code below inside DrawGLScene(), after InitGL().

It won't need any other initialization.

But make sure you execute it before any change of projection (e.g. 2D projection for drawing on the position of the coords you get back).

GLdouble x, y, z; // target 2d coords (z is 'unused')
GLdouble coords[] = { 1.0, 1.0, 1.0 }; // current 3d coords

GLdouble model_view[16];
glGetDoublev(GL_MODELVIEW_MATRIX, model_view);

GLdouble projection[16];
glGetDoublev(GL_PROJECTION_MATRIX, projection);

GLint viewport[4];
glGetIntegerv(GL_VIEWPORT, viewport);

// get window coords based on 3D coordinates
gluProject( coords[0], coords[1], coords[2],
            model_view, projection, viewport,
            &x, &y, &z);

Description of gluProject parameters

An example of gluUnproject where I have the code from

Upvotes: 4

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