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nick2price

OpenGL problem understanding cameras

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I am having a real problem understanding cameras in opengl. I will show two bits of code at the bottom. The first class creates a skymap and imports a model car (different methods). The second class is like my main, where i call up my methods etc. The first thing i would like to know is at the moment, my view (camera) is in the middle of my skybox. What function in my code put it there or is this just where it is placed by default? The second thing i would like to find out is how to get a rotating camera from the point it is currently at (the midlle of the screen). Would this be carried out in my main class? Where do i get my values from for all the glrotate or gluLookAt? Any advise to my questions would be brilliant. thanks
 
#include "stdafx.h"
#include <GL/glut.h>
#include <windows.h>
#include <stdio.h>  //for file access							
#include <gl\gl.h>													
#include "skybox.h"
#include "glbmp.h"
#include "coursework2.h"
#include "3dsloader.h"
#include "texture.h"

obj_type object;

bool skybox::LoadTexture(unsigned int & aTexture, const char * bitmap_file)
{
   glbmp_t bitmap;     //object to fill with data from glbmp
 

   if(!glbmp_LoadBitmap(bitmap_file, 0, &bitmap))
   {
      fprintf(stderr, "Error loading bitmap file: %s\n", bitmap_file);
   }
 
   //generate and bind the OpenGL texture
   glGenTextures(1, &aTexture);
   glBindTexture(GL_TEXTURE_2D, aTexture);
 
   //copy data from bitmap into texture
   glTexImage2D(GL_TEXTURE_2D, 0, 3, bitmap.width, bitmap.height,
                0, GL_RGB, GL_UNSIGNED_BYTE, bitmap.rgb_data);
 
   //set up texture filtering
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
 
   //free the bitmap
   glbmp_FreeBitmap(&bitmap);
 
   return true;
}
 


void skybox::Init() {

	OFFSET = 1/512.0; //set offset value for skybox

	rot_x = 0.0; rot_y = 0.0;

  

	LoadTexture(texture[0], "images/1.bmp");
	LoadTexture(texture[1], "images/2.bmp");
	LoadTexture(texture[2], "images/3.bmp");
	LoadTexture(texture[3], "images/4.bmp");
	LoadTexture(texture[4], "images/5.bmp");
	LoadTexture(texture[5], "images/6.bmp");

}

void skybox::Init2(){



	glClearColor(0.0, 0.0, 0.0, 0.0); // This clear the background color to black
    glShadeModel(GL_SMOOTH); // Type of shading for the polygons
   	
   
    // Projection transformation
    glMatrixMode(GL_PROJECTION); // Specifies which matrix stack is the target for matrix operations 
    glLoadIdentity(); // initialize the projection matrix as identity
//    gluPerspective(45.0f,(GLfloat)screen_width/(GLfloat)screen_height,10.0f,10000.0f); // define the "viewing volume"
   
    glEnable(GL_DEPTH_TEST); // enable the depth test (also called z buffer)
    glPolygonMode (GL_FRONT_AND_BACK, GL_FILL); // Polygon rasterization mode (polygon filled)
    
    glEnable(GL_TEXTURE_2D); // This Enable the Texture mapping

    Load3DS (&object,"GTR.3ds");

    object.id_texture=LoadBitmap("body.bmp"); // The Function LoadBitmap() return the current texture ID
    

}

//This is where the magic happens
void skybox::draw() {

	glPushMatrix();
	glRotated(rot_x, 1.0, 0.0, 0.0);	//Rotate around the x axis
	glRotated(rot_y, 0.0, 1.0, 0.0);	//Rotate around the y axis

	glColor3f(1.0f,1.0f,1.0f);			//Set colour to White
	glEnable(GL_TEXTURE_2D);			//Enable texture mapping
	glDisable (GL_DEPTH_TEST);			//Disable depth testing

		//before you can use a texture you have to bind it
		glBindTexture(GL_TEXTURE_2D, texture[0 + text_offset]);

		glBegin (GL_QUADS);	
		
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET,0.0 + OFFSET);	glVertex3d (-10.0,-10.0,10.0);
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET,0.0 + OFFSET);	glVertex3d (-10.0,-10.0,-10.0);
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET,1.0 - OFFSET);	glVertex3d (-10.0,10.0,-10.0);
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET,1.0 - OFFSET);	glVertex3d (-10.0,10.0,10.0);

		glEnd ();				

		glBindTexture(GL_TEXTURE_2D, texture[1 + text_offset]);
		glBegin (GL_QUADS);
		
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET,0.0 + OFFSET);	glVertex3d (-10.0,-10.0,-10.0);
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET,0.0 + OFFSET);	glVertex3d (10.0,-10.0,-10.0);
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET,1.0 - OFFSET);	glVertex3d (10.0,10.0,-10.0);
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET,1.0 - OFFSET);	glVertex3d (-10.0,10.0,-10.0);
		glEnd ();

		glBindTexture(GL_TEXTURE_2D, texture[2 + text_offset]);
		glBegin (GL_QUADS);
		
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET ,0.0 + OFFSET); glVertex3d (10.0,-10.0,-10.0);
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,0.0 + OFFSET); glVertex3d (10.0,-10.0,10.0);
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,1.0 - OFFSET); glVertex3d (10.0,10.0,10.0);
				glNormal3d (0.0,0.0,10.0); glTexCoord2d (0.0 + OFFSET ,1.0 - OFFSET); glVertex3d (10.0,10.0,-10.0);

		glEnd ();

		glBindTexture(GL_TEXTURE_2D, texture[3 + text_offset]);	
		glBegin (GL_QUADS);
			
			glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET ,0.0 + OFFSET); glVertex3d (10.0,-10.0,10.0);
			glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,0.0 + OFFSET); glVertex3d (-10.0,-10.0,10.0);
			glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,1.0 - OFFSET); glVertex3d (-10.0,10.0,10.0);
			glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET ,1.0 - OFFSET); glVertex3d (10.0,10.0,10.0);
		
		glEnd ();

		glBindTexture(GL_TEXTURE_2D, texture[4 + text_offset]);	
		glBegin (GL_QUADS);
			
			glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET ,0.0 + OFFSET); glVertex3d (-10.0,-10.0,10.0);
			glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,0.0 + OFFSET); glVertex3d (10.0,-10.0,10.0);
			glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,1.0 - OFFSET); glVertex3d (10.0,-10.0,-10.0);
			glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET ,1.0 - OFFSET); glVertex3d (-10.0,-10.0,-10.0);
		
		glEnd ();

		glBindTexture(GL_TEXTURE_2D, texture[5 + text_offset]);
		glBegin (GL_QUADS);
		
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET ,0.0 + OFFSET); glVertex3d (-10.0,10.0,-10.0);
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,0.0 + OFFSET); glVertex3d (10.0,10.0,-10.0);
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,1.0 - OFFSET); glVertex3d (10.0,10.0,10.0);
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET ,1.0 - OFFSET); glVertex3d (-10.0,10.0,10.0);
				
		glEnd ();

	//Re-Enable the depth test
	glEnable(GL_DEPTH_TEST);
	//disable texture mapping
	glDisable(GL_TEXTURE_2D);
	glPopMatrix();
	

}

void skybox::draw_car(void){

	int l_index;
    
    glMatrixMode(GL_MODELVIEW); // Modeling transformation
    glLoadIdentity(); // Initialize the model matrix as identity
    
    glTranslatef(0.0,0.0,-300); // move the object forward (the model matrix is multiplied by the translation matrix)
 

    
    glBindTexture(GL_TEXTURE_2D, object.id_texture); // set the active texture 

    glBegin(GL_TRIANGLES);
    for (l_index=0;l_index<object.polygons_qty;l_index++)
    {
        //----------------- FIRST VERTEX -----------------
        // Texture coordinates of the first vertex
        glTexCoord2f( object.mapcoord[ object.polygon[l_index].a ].u,
                      object.mapcoord[ object.polygon[l_index].a ].v);
        // Coordinates of the first vertex
        glVertex3f( object.vertex[ object.polygon[l_index].a ].x,
                    object.vertex[ object.polygon[l_index].a ].y,
                    object.vertex[ object.polygon[l_index].a ].z); //Vertex definition

        //----------------- SECOND VERTEX -----------------
        // Texture coordinates of the second vertex
        glTexCoord2f( object.mapcoord[ object.polygon[l_index].b ].u,
                      object.mapcoord[ object.polygon[l_index].b ].v);
        // Coordinates of the second vertex
        glVertex3f( object.vertex[ object.polygon[l_index].b ].x,
                    object.vertex[ object.polygon[l_index].b ].y,
                    object.vertex[ object.polygon[l_index].b ].z);
        
        //----------------- THIRD VERTEX -----------------
        // Texture coordinates of the third vertex
        glTexCoord2f( object.mapcoord[ object.polygon[l_index].c ].u,
                      object.mapcoord[ object.polygon[l_index].c ].v);
        // Coordinates of the Third vertex
        glVertex3f( object.vertex[ object.polygon[l_index].c ].x,
                    object.vertex[ object.polygon[l_index].c ].y,
                    object.vertex[ object.polygon[l_index].c ].z);
    }
    glEnd();

 

}

main class
#include "stdafx.h"
#include <GL/glut.h>
#include <windows.h>
#include <stdio.h>  //for file access							
#include <gl\gl.h>													
#include "skybox.h"
#include "glbmp.h"
#include "coursework2.h"
#include "3dsloader.h"
#include "texture.h"

int screen_width=800;
int screen_height=600;

skybox		aSkyBox;

GLvoid ReSizeGLScene(GLsizei width, GLsizei height) {

	if (height<=0) { height=1; }

	glViewport(0,0,width,height);

	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();

	gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);

	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
}

int InitGL(GLvoid) {
	
	glEnable(GL_TEXTURE_2D);
	glShadeModel(GL_SMOOTH);							//Try GL_FLAT to see the difference
	glClearColor(0.0f, 0.0f, 0.0f, 1.0f);				//Background colour
	glClearDepth(1.0f);
	glEnable(GL_DEPTH_TEST);							//Enables depth testing
	glDepthFunc(GL_LEQUAL);								//Specifies how Depth testing is done
	glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);	//Affects quality of colour and texture interpolation
	glFrontFace (GL_CCW);								//Specifies that the front of a face is defined 
														//in a Counter Clockwise manner
	glCullFace(GL_BACK);								//Specifies that the back of faces are not shown
														//so OpenGL does not need to draw things twice
	glEnable(GL_CULL_FACE);								//Enables culling of faces


	aSkyBox.Init();			//Initalize the Skybox
    aSkyBox.Init2();

	return TRUE;
}

void DrawGLScene(GLvoid) {

	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glLoadIdentity();

	aSkyBox.draw();
	aSkyBox.draw_car();
	glutSwapBuffers(); 
 
}

int main(int argc, char **argv)
{
    glutInit(&argc, argv);    
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
    glutInitWindowSize(screen_width,screen_height);
    glutInitWindowPosition(0,0);
    glutCreateWindow("Coursework 2");    
 
	glutReshapeFunc(ReSizeGLScene);
	glutDisplayFunc(DrawGLScene);
	InitGL();
    glutMainLoop();

    return(0);    
}

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