OpenGL SkyBox not showing - c++

Question

I'm making a skybox in openGL c++, now I followed some tutorials on skyboxes, I have the image's all set up but my skybox doesn't get drawn at all! (I only see black opengl background)
So here is my code, what can be the problem? I'm looking at it for hours and can't find a thing, I'm new at openGL so if you spot any bad code please do tell! Thanks!
#include <iostream>
#include <stdlib.h>
#ifdef __APPLE__
#include <OpenGL/OpenGL.h>
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif
#include "imageloader.h"
using namespace std;
//angle of rotation
GLfloat xpos = 0, ypos = 0, zpos = 0, xrot = 0, yrot = 0, angle=0.0;
GLuint _textureId; //The OpenGL id of the texture
GLuint _skybox[5];
float lastx, lasty;
bool leftMouseButton = false;
float PI = 3.141592654f;
//Makes the image into a texture, and returns the id of the texture
GLuint __loadTexture(Image* image) {
GLuint textureId;
glGenTextures(1, &textureId);
glBindTexture(GL_TEXTURE_2D, textureId);
glTexImage2D(GL_TEXTURE_2D,
0,
GL_RGB,
image->width, image->height,
0,
GL_RGB,
GL_UNSIGNED_BYTE,
image->pixels);
return textureId;
}
GLuint __loadMipmappedTexture(Image *image) {
GLuint textureId;
glGenTextures(1, &textureId);
glBindTexture(GL_TEXTURE_2D, textureId);
gluBuild2DMipmaps(GL_TEXTURE_2D,
GL_RGB,
image->width, image->height,
GL_RGB,
GL_UNSIGNED_BYTE,
image->pixels);
return textureId;
}
void initRendering() {
glEnable(GL_DEPTH_TEST);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glEnable(GL_NORMALIZE);
glEnable(GL_COLOR_MATERIAL);
glEnable(GL_CULL_FACE);
glShadeModel (GL_SMOOTH); //set the shader to smooth shader
Image* image = loadBMP("artesis.bmp");
_textureId = __loadMipmappedTexture(image);
image = loadBMP("skybox/deep_ft.bmp");
_skybox[0] = __loadMipmappedTexture(image);
image = loadBMP("skybox/deep_lf.bmp");
_skybox[1] = __loadMipmappedTexture(image);
image = loadBMP("skybox/deep_bk.bmp");
_skybox[2] = __loadMipmappedTexture(image);
image = loadBMP("skybox/deep_rt.bmp");
_skybox[3] = __loadMipmappedTexture(image);
image = loadBMP("skybox/deep_up.bmp");
_skybox[4] = __loadMipmappedTexture(image);
image = loadBMP("skybox/deep_dn.bmp");
_skybox[5] = __loadMipmappedTexture(image);
delete image;
}
void handleResize(int w, int h) {
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0, (double)w / (double)h, 1.0, 100.0);
glViewport (0, 0, w, h);
glMatrixMode(GL_MODELVIEW);
glutPostRedisplay();
}
void mouseMovement(int x, int y) {
if (leftMouseButton == true)
{
GLfloat diffx = (x-lastx)/20; //check the difference between the current x and the last x position
GLfloat diffy = (y-lasty)/20; //check the difference between the current y and the last y position
lastx = x; //set lastx to the current x position
lasty = y; //set lasty to the current y position
xrot += (float) diffy; //set the xrot to xrot with the addition of the difference in the y position
yrot += (float) diffx; //set the xrot to yrot with the addition of the difference in the x position
}
else if( leftMouseButton == false)
{
GLfloat diffx = x-lastx; //check the difference between the current x and the last x position
GLfloat diffy = y-lasty; //check the difference between the current y and the last y position
lastx = x; //set lastx to the current x position
lasty = y; //set lasty to the current y position
}
}
void mouseButtons(int button, int state, int x, int y) {
if ((state == GLUT_DOWN) && (button == GLUT_LEFT_BUTTON))
{
leftMouseButton = true;
}
else if ((state == GLUT_DOWN) && (button == GLUT_RIGHT_BUTTON))
{
leftMouseButton = false;
}
}
void drawGrid(float size, float step)
{
// disable lighting
glDisable(GL_LIGHTING);
glBegin(GL_LINES);
glColor3f(0.3f, 0.3f, 0.3f);
for(float i=step; i <= size; i+= step)
{
glVertex3f(-size, 0, i); // lines parallel to X-axis
glVertex3f( size, 0, i);
glVertex3f(-size, 0, -i); // lines parallel to X-axis
glVertex3f( size, 0, -i);
glVertex3f( i, 0, -size); // lines parallel to Z-axis
glVertex3f( i, 0, size);
glVertex3f(-i, 0, -size); // lines parallel to Z-axis
glVertex3f(-i, 0, size);
}
// x-axis
glColor3f(0.5f, 0, 0);
glVertex3f(-size, 0, 0);
glVertex3f( size, 0, 0);
// z-axis
glColor3f(0,0,0.5f);
glVertex3f(0, 0, -size);
glVertex3f(0, 0, size);
glEnd();
// enable lighting back
glEnable(GL_LIGHTING);
}
void keyboard (unsigned char key, int x, int y) {
float xrotrad, yrotrad;
switch(key) {
case 'a':
xrot += 1;
if(xrot > 360) xrot -= 360;
break;
case 'w':
xrot -= 1;
if(xrot < -360) xrot += 360;
break;
case 'z':
yrotrad = (yrot / 180 * PI);
xrotrad = (xrot / 180 * PI);
xpos += float(sin(yrotrad));
zpos -= float(cos(yrotrad));
ypos -= float(sin(xrotrad));
break;
case 's':
yrotrad = (yrot / 180 * PI);
xrotrad = (xrot / 180 * PI);
xpos -= float(sin(yrotrad));
zpos += float(cos(yrotrad));
ypos += float(sin(xrotrad));
break;
case 'd':
yrot += 1;
if (yrot >360) yrot -= 360;
break;
case 'q':
yrot -= 1;
if (yrot < -360)yrot += 360;
break;
case 27:
exit(0);
break;
}
}
void camera (void) {
glRotatef(xrot,1.0,0.0,0.0); //rotate our camera on teh x-axis (left and right)
glRotatef(yrot,0.0,1.0,0.0); //rotate our camera on the y-axis (up and down)
glTranslated(-xpos,-ypos,-zpos); //translate the screen to the position of our camera
}
void drawScene() {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
GLfloat lightKa[] = {.0f, .0f, .0f, 1.0f}; // ambient light
GLfloat lightKd[] = {.9f, .9f, .9f, 1.0f}; // diffuse light
GLfloat lightKs[] = {1, 1, 1, 1}; // specular light
glLightfv(GL_LIGHT0, GL_AMBIENT, lightKa);
glLightfv(GL_LIGHT0, GL_DIFFUSE, lightKd);
glLightfv(GL_LIGHT0, GL_SPECULAR, lightKs);
// position the light
float lightPos[4] = {0, 10, 10, 0};
glLightfv(GL_LIGHT0, GL_POSITION, lightPos);
camera();
//call the skybox
// Store the current matrix
glPushMatrix();
// Reset and transform the matrix.
glLoadIdentity();
/* EDIT: I really dont know how to set gluLookAt, I guess it should be the camera positions??? */
gluLookAt(
0.0,0.0,0.0,
0.1, 0.0, 0.1,
0.0,1.0,0.0);
// Enable/Disable features
glPushAttrib(GL_ENABLE_BIT);
glEnable(GL_TEXTURE_2D);
glDisable(GL_DEPTH_TEST);
glDepthMask(false);
glDisable(GL_LIGHTING);
glDisable(GL_BLEND);
// Just in case we set all vertices to white.
glColor4f(1,1,1,1);
// Render the front quad
glBindTexture(GL_TEXTURE_2D, _skybox[0]);
glBegin(GL_QUADS);
glTexCoord2f(0, 0); glVertex3f( 0.5f, -0.5f, -0.5f );
glTexCoord2f(1, 0); glVertex3f( -0.5f, -0.5f, -0.5f );
glTexCoord2f(1, 1); glVertex3f( -0.5f, 0.5f, -0.5f );
glTexCoord2f(0, 1); glVertex3f( 0.5f, 0.5f, -0.5f );
glEnd();
// Render the left quad
glBindTexture(GL_TEXTURE_2D, _skybox[1]);
glBegin(GL_QUADS);
glTexCoord2f(0, 0); glVertex3f( 0.5f, -0.5f, 0.5f );
glTexCoord2f(1, 0); glVertex3f( 0.5f, -0.5f, -0.5f );
glTexCoord2f(1, 1); glVertex3f( 0.5f, 0.5f, -0.5f );
glTexCoord2f(0, 1); glVertex3f( 0.5f, 0.5f, 0.5f );
glEnd();
// Render the back quad
glBindTexture(GL_TEXTURE_2D, _skybox[2]);
glBegin(GL_QUADS);
glTexCoord2f(0, 0); glVertex3f( -0.5f, -0.5f, 0.5f );
glTexCoord2f(1, 0); glVertex3f( 0.5f, -0.5f, 0.5f );
glTexCoord2f(1, 1); glVertex3f( 0.5f, 0.5f, 0.5f );
glTexCoord2f(0, 1); glVertex3f( -0.5f, 0.5f, 0.5f );
glEnd();
// Render the right quad
glBindTexture(GL_TEXTURE_2D, _skybox[3]);
glBegin(GL_QUADS);
glTexCoord2f(0, 0); glVertex3f( -0.5f, -0.5f, -0.5f );
glTexCoord2f(1, 0); glVertex3f( -0.5f, -0.5f, 0.5f );
glTexCoord2f(1, 1); glVertex3f( -0.5f, 0.5f, 0.5f );
glTexCoord2f(0, 1); glVertex3f( -0.5f, 0.5f, -0.5f );
glEnd();
// Render the top quad
glBindTexture(GL_TEXTURE_2D, _skybox[4]);
glBegin(GL_QUADS);
glTexCoord2f(0, 1); glVertex3f( -0.5f, 0.5f, -0.5f );
glTexCoord2f(0, 0); glVertex3f( -0.5f, 0.5f, 0.5f );
glTexCoord2f(1, 0); glVertex3f( 0.5f, 0.5f, 0.5f );
glTexCoord2f(1, 1); glVertex3f( 0.5f, 0.5f, -0.5f );
glEnd();
// Render the bottom quad
glBindTexture(GL_TEXTURE_2D, _skybox[5]);
glBegin(GL_QUADS);
glTexCoord2f(0, 0); glVertex3f( -0.5f, -0.5f, -0.5f );
glTexCoord2f(0, 1); glVertex3f( -0.5f, -0.5f, 0.5f );
glTexCoord2f(1, 1); glVertex3f( 0.5f, -0.5f, 0.5f );
glTexCoord2f(1, 0); glVertex3f( 0.5f, -0.5f, -0.5f );
glEnd();
// Restore enable bits and matrix
glPopAttrib();
glPopMatrix();
glEnable(GL_DEPTH_TEST);
glEnable(GL_LIGHTING);
glEnable(GL_BLEND);
glDepthMask(true);
glClear(GL_DEPTH_BUFFER_BIT);
drawGrid(20, 1);
glutSwapBuffers(); //swap the buffers
}
void update(int value) {
angle++; //increase the angle
glutPostRedisplay(); //Tell GLUT that the display has changed
//Tell GLUT to call update again in 25 milliseconds
glutTimerFunc(25, update, 0);
}
int main(int argc, char** argv) {
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowSize(800, 800);
glutCreateWindow("Block Position");
initRendering();
glutDisplayFunc(drawScene);
glutKeyboardFunc(keyboard);
glutIdleFunc(drawScene);
glutReshapeFunc(handleResize);
glutPassiveMotionFunc(mouseMovement);
glutTimerFunc(25, update, 0); //Add a timer
glutMouseFunc(mouseButtons);
glutMainLoop();
return 0;
}

Answer 1

If nothing is appearing at all, it may be because the sky box isn't in the scene because it's being culled (or not rendered) onto the screen.
In your code you specify 100.0 for the zFar:
gluPerspective(45.0, (double)w / (double)h, 1.0, 100.0);
Change the zFar value to accommodate for the size of the sky box (say 500.0) and it should appear.

Answer 2

You should start with minimal rendering, like no lightning, no face culling, just triangles in white color. So if you see white then at least your camera position is probably OK. Then you can enable culling, if all disappears then this is your problem - normals are in wrong directions. Then if all is OK, enable lighting, then texturing - and always check what changes.
so dont look at it too hard, but eliminate complexity - even check if simple trianlge will show up in the expected position.