how to change integer values of glLookat view elements with keyboard? - c++

Question

I am making a room and i want to change the values of lookat because i want to move my camera up,down,right,left,forward and backward inside my room.
My code is given below with comments:
#include <iostream>
using namespace std;
#include "glut.h"
#include "GL/gl.h"
//---------------------------------------------------------------------
static int all =0;
static int allD =0;
static int a=0;
static int d=0;
static int o=0;
static float w=0;
static float s=0;
//---------------------------------------------------------------------
void init(void)
{
glClearColor(0.0,0.0,0.0,0.0);
glShadeModel(GL_FLAT);
}
//---------------------------------------------------------------------
void display(void)
{
glClear(GL_COLOR_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
//glEnable(GL_DEPTH);
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
//glDisable(GL_DEPTH_TEST);
glPushMatrix();
glRotatef(a,0,1,0);
glRotatef(d,0,1,0);
//back wall glPushMatrix();
glTranslatef(0,0,-2);
glColor3f(0.5,1,0);
glScalef (50.0, 20.0, 2);
glutSolidCube (0.5);
glPopMatrix();
//left wall glPushMatrix();
glTranslatef(-12,0,4.5);
glColor3f(1,1,0);
glScalef (2, 20, 25);
glutSolidCube (0.5);
glPopMatrix();
//floor glPushMatrix();
glTranslatef(0,-5,4.5);
glColor3f(0.5,1,1);
glScalef (50, 0.2, 25);
glutSolidCube (0.5);
glPopMatrix();
//roof glPushMatrix();
glTranslatef(0,4.5,4.5);
glColor3f(0,0,1);
glScalef (50, 2, 25);
glutSolidCube (0.5);
glPopMatrix();
//right wall glPushMatrix();
glTranslatef(12,0,4.5);
glColor3f(0.8,0.2,1);
glScalef (2, 20, 25);
glutSolidCube (0.5);
glPopMatrix();
////front wall 1 //glPushMatrix();
// glTranslatef(-2,0,9);
// glColor3f(0.5,0,0);
// glScalef (12.0, 20.0, 2);
// glutSolidCube (0.5);
//glPopMatrix();
////front wall 2 //glPushMatrix();
// glTranslatef(2.5,2.5,9);
// glColor3f(0.5,0,0);
// glScalef (10.0, 10.0, 2);
// glutSolidCube (0.5);
//glPopMatrix();
////Door //glPushMatrix();
// glTranslatef(0.8,-2,9);
// glRotatef(o,0,1,0);
// glColor3f(0.5,0.5,0.5);
// glScalef (1.0, 8.0, 0.2);
// glutSolidCube (0.5);
//glPushMatrix();
// glTranslatef(1.7,0,0);
// glColor3f(0.5,0.5,0.5);
// glScalef (6.0, 1.5, 0.2);
// glutSolidCube (0.5);
//glPopMatrix();
//glPopMatrix();
//table glPopMatrix();
glutPostRedisplay();
glutSwapBuffers();
}
//---------------------------------------------------------------------
void reshape (int w, int h)
{
glViewport (0, 0, (GLsizei) w, (GLsizei) h);
glMatrixMode (GL_PROJECTION);
glLoadIdentity ();
gluPerspective(65, (GLfloat) w/(GLfloat) h, 1.0, 100.0);
//glFrustum(-2,2,-2,2,2.5,20);
//glOrtho(-2,2,-2,2,2.5,20);
gluLookAt (0.0, 0.0, 25, w, s, 0.0, 0.0, 1.0, 0.0);
//i made it 'w' and 's' but its not working. glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
//---------------------------------------------------------------------
void keyboard (unsigned char key, int x, int y)
{
switch (key)
{
case 'a': a = (a - 1) % 360;
glutPostRedisplay();
break;
case 'd': d = (d + 1) % 360;
glutPostRedisplay();
break;
case 'o': o = (o + 1) % 90;
glutPostRedisplay();
break;
case 'w': w = (w + 0.1) ;
glutPostRedisplay();
break;
case 's': s = (s - 0.1);
glutPostRedisplay();
break;
default: break;
}
}
//---------------------------------------------------------------------
void SpecialKeys(int key, int x, int y)
{
switch (key)
{
case GLUT_KEY_RIGHT : all = (all + 10) % 360;
glutPostRedisplay();
break;
case GLUT_KEY_UP : allD = (allD - 10) % 360;
glutPostRedisplay();
break;
case GLUT_KEY_LEFT : all = (all - 10) % 360;
glutPostRedisplay();
break;
case GLUT_KEY_DOWN : allD = (allD + 10) % 360;
glutPostRedisplay();
break;
default: break;
}
}
//---------------------------------------------------------------------
int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB);
glutInitWindowSize (700, 500);
glutInitWindowPosition (0,0);
glutCreateWindow (argv[0]);
init ();
glutDisplayFunc(display);
glutSpecialFunc(SpecialKeys);
glutReshapeFunc(reshape);
glutKeyboardFunc(keyboard);
glutMainLoop();
return 0;
}
//

Answer 1

You need to re-execute the gluLookAt() function whenever you update the values you're passing to it.
A cleaner way to execute this part of your code would be:
static int W = 0;
static int H = 0;
static int S = 0;
//---------------------------------------------------------------------
void updateCamera() {
gluLookAt (0.0, 0.0, 25, W, S, 0.0, 0.0, 1.0, 0.0);
}
//---------------------------------------------------------------------
void reshape (int w, int h)
{
W = w;
H = h;
glViewport (0, 0, (GLsizei) w, (GLsizei) h);
glMatrixMode (GL_PROJECTION);
glLoadIdentity ();
gluPerspective(65, (GLfloat) w/(GLfloat) h, 1.0, 100.0);
//glFrustum(-2,2,-2,2,2.5,20);
//glOrtho(-2,2,-2,2,2.5,20);
updateCamera();
glLoadIdentity();
}
//---------------------------------------------------------------------
void keyboard (unsigned char key, int x, int y)
{
switch (key)
{
case 'a':
a = (a - 1) % 360;
break;
case 'd':
d = (d + 1) % 360;
break;
case 'o':
o = (o + 1) % 90;
break;
case 'w':
W = (W + 0.1) ;
updateCamera();
break;
case 's':
S = (S - 0.1);
updateCamera();
break;
default: break;
}
glutPostRedisplay();
}
In general, it's a good idea to abstract out the calls you make often and/or from different places so that you aren't copy-pasting and making future updates or bug fixes more difficult.