Is there a way to cycle options in C++/GLUT - c++

I am making a program that will cycle the color of a triangle with the up and down arrows. I am pretty new to GLUT and C++, so I can't figure out a way to "cycle" colors.
Here is the triangle code:
void render(void) {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
gluLookAt( 0.0f, 0.0f, 10.0f,
0.0f, 0.0f, 0.0f,
0.0f, 1.0f, 0.0f);
glRotatef(angle, 0.0f, 1.0f, 0.0f);
glColor3f(red, green, blue);
glBegin(GL_TRIANGLES);
glVertex3f(-2, 0, 0.0);
glVertex3f(2, 0, 0.0);
glVertex3f(2, 2, 0.0);
glEnd();
angle+=0.1f;
glutSwapBuffers();
}
and the input code:
void processSpecialKey(int key, int x, int y) {
switch(key) {
case GLUT_KEY_UP :
red += 1.0;
green += 0.0;
blue += 0.0; break;
case GLUT_KEY_DOWN :
red += 0.0;
green += 1.0;
blue += 0.0; break;
}
}

Related

Can't draw hexagonal prism when I press a key in OpenGL

I tried to draw a hexagonal prism when I press a key but I have a big problem: it is drawn a random shape by default on the screen..this is my code. When I press p it is showned a pyramid, when I press c I can see a cube but by default it is drawn a random shape and I don't understand why... this is my code and the sample photo:
#include <stdlib.h>
#include <math.h>
#include "dependente\freeglut\freeglut.h"
#include "dependente\glfw\glfw3.h"
#include <stdio.h> //incluziuni librarii
#define RADDEG 57.29577951f //constanta
float XUP[3] = { 1,0,0 }, XUN[3] = { -1, 0, 0 }, //vector coordonate
YUP[3] = { 0,1,0 }, YUN[3] = { 0,-1, 0 },
ZUP[3] = { 0,0,1 }, ZUN[3] = { 0, 0,-1 },
ORG[3] = { 0,0,0 };
GLfloat viewangle = 0, tippangle = 0, traj[120][3]; //variabila pentru unghi camera
GLfloat d[3] = { 0.1, 0.1, 0.1 }; //vector directie
GLfloat xAngle = 0.0, yAngle = 0.0, zAngle = 0.0;
bool draw_pyramid = false; //variabila desenat figuri
bool draw_box = false;
bool draw_prism = false;
// Use arrow keys to rotate entire scene !!!
void Special_Keys(int key, int x, int y) //functie ptr taste sus jos stanga dreapta
{
switch (key) {
case GLUT_KEY_LEFT: viewangle -= 5; break;
case GLUT_KEY_RIGHT: viewangle += 5; break;
case GLUT_KEY_UP: tippangle -= 5; break;
case GLUT_KEY_DOWN: tippangle += 5; break;
default: printf("Special key %c == %d", key, key);
}
glutPostRedisplay();
}
void Pyramid(void) //draw the pyramid shape
{
glBegin(GL_TRIANGLE_FAN);//triangles have a common vertex, which is the central vertex
glColor3f(1.0f, 0.0f, 0.0f); glVertex3f(0.0f, 1.0f, 0.0f); //V0(red)
glColor3f(0.0f, 1.0f, 0.0f); glVertex3f(-1.0f, -1.0f, 1.0f); //V1(green)
glColor3f(0.0f, 0.0f, 1.0f); glVertex3f(1.0f, -1.0f, 1.0f); //V2(blue)
glColor3f(0.0f, 1.0f, 0.0f); glVertex3f(1.0f, -1.0f, -1.0f); //V3(green)
glColor3f(0.0f, 0.0f, 1.0f); glVertex3f(-1.0f, -1.0f, -1.0f); //V4(blue)
glColor3f(0.0f, 1.0f, 0.0f); glVertex3f(-1.0f, -1.0f, 1.0f); //V1(green)
glEnd();
}
void Draw_Box(void) //functie desenat cub
{
glBegin(GL_QUADS);//// Draw A Quad
glColor3f(0.0, 0.7, 0.1); // Front - green
glVertex3f(-1.0, 1.0, 1.0);
glVertex3f(1.0, 1.0, 1.0);
glVertex3f(1.0, -1.0, 1.0);
glVertex3f(-1.0, -1.0, 1.0);
glColor3f(0.9, 1.0, 0.0); // Back - yellow
glVertex3f(-1.0, 1.0, -1.0);
glVertex3f(1.0, 1.0, -1.0);
glVertex3f(1.0, -1.0, -1.0);
glVertex3f(-1.0, -1.0, -1.0);
glColor3f(0.2, 0.2, 1.0); // Top - blue
glVertex3f(-1.0, 1.0, 1.0);
glVertex3f(1.0, 1.0, 1.0);
glVertex3f(1.0, 1.0, -1.0);
glVertex3f(-1.0, 1.0, -1.0);
glColor3f(0.7, 0.0, 0.1); // Bottom - red
glVertex3f(-1.0, -1.0, 1.0);
glVertex3f(1.0, -1.0, 1.0);
glVertex3f(1.0, -1.0, -1.0);
glVertex3f(-1.0, -1.0, -1.0);
glEnd();
}
void hexagonalPrism()
{
glBegin(GL_QUADS);
glVertex3f(0.5, 0, 0.5);
glVertex3f(0.5, 0, -0.5);
glVertex3f(-0.5, 0, -0.5);
glVertex3f(-0.5, 0, 0.5);
glVertex3f(0.5, 0, -0.5);
glVertex3f(0.5, 1, -0.5);
glVertex3f(-0.5, 1, -0.5);
glVertex3f(-0.5, 0, -0.5);
glVertex3f(0.5, 1, -0.5);
glVertex3f(-0.5, 1, -0.5);
glVertex3f(-0.5, 0, 0.5);
glVertex3f(0.5, 0, 0.5);
glEnd();
glBegin(GL_TRIANGLES);
glVertex3f(0.5, 0, 0.5);
glVertex3f(0.5, 1, -0.5);
glVertex3f(0.5, 0, -0.5);
glVertex3f(-0.5, 0, 0.5);
glVertex3f(-0.5, 1, -0.5);
glVertex3f(-0.5, 0, -0.5);
glEnd();
}
void Keyboard(unsigned char key, int x, int y) //press a key to perform actions
{
switch (key) {
case 'd': d[0] += 0.1; break; //camera right
case 'a': d[0] -= 0.1; break; //camera left
case 'w': d[1] += 0.1; break; //camera up
case 's': d[1] -= 0.1; break; //camera down
case 'm': d[2] += 0.1; break; //magnify
case 'n': d[2] -= 0.1; break; //minify
case 'p': draw_pyramid = true; draw_box = false; break; //draw pyramid when key is pressed
case 'c': draw_box = true; draw_pyramid = false; break; //draw cube when key is pressed
case 't': draw_box = false; draw_pyramid = false; draw_prism = true; break; //draw prism when key is pressed
case 'x': xAngle += 5; break; //modify x axis angle
case 'y': yAngle += 5; break; //modify y axis angle
case 'z': zAngle += 5; break; //modify z axis angle
default: printf(" Keyboard %c == %d", key, key); //see what key it's pressed
}
glutPostRedisplay();
}
void Triad(void)
{
glColor3f(1.0, 1.0, 1.0); //set the dark grey color
glBegin(GL_LINES);
glVertex3fv(ORG); glVertex3fv(XUP);
glVertex3fv(ORG); glVertex3fv(YUP);
glVertex3fv(ORG); glVertex3fv(ZUP);
glEnd();
glRasterPos3f(1.1, 0.0, 0.0);
glutBitmapCharacter(GLUT_BITMAP_HELVETICA_18, 'X'); //draw the x axis
glRasterPos3f(0.0, 1.1, 0.0);
glutBitmapCharacter(GLUT_BITMAP_HELVETICA_18, 'Y'); //draw the y axis
glRasterPos3f(0.0, 0.0, 1.1);
glutBitmapCharacter(GLUT_BITMAP_HELVETICA_18, 'Z'); //draw the z axis
}
void redraw(void)
{
int v;
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
glLoadIdentity();
glTranslatef(0, 0, -3);
glRotatef(tippangle, 1, 0, 0); // Up and down arrow keys 'tip' view.
glRotatef(viewangle, 0, 1, 0); // Right/left arrow keys 'turn' view.
glDisable(GL_LIGHTING);
Triad();
glPushMatrix();
glTranslatef(d[0], d[1], d[2]); // Move box down X axis.
glScalef(0.2, 0.2, 0.2);
glRotatef(zAngle, 0, 0, 1);
glRotatef(yAngle, 0, 1, 0);
glRotatef(xAngle, 1, 0, 0);
if ( draw_pyramid )
Pyramid();
if (hexagonalPrism)
hexagonalPrism();
if ( draw_box )
Draw_Box();
glPopMatrix();
glutSwapBuffers();
}
int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitWindowSize(900, 600);
glutInitWindowPosition(300, 300);
glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE);
glutCreateWindow("Big HW1");
glutDisplayFunc(redraw);
glutKeyboardFunc(Keyboard);
glutSpecialFunc(Special_Keys);
glClearColor(0.1, 0.0, 0.1, 1.0);
glMatrixMode(GL_PROJECTION);//specify which matrix is the current matrix, matrix that represents your camera's lens (aperture, far-field, near-field, etc).
gluPerspective(60, 1.5, 1, 10); //set up a perspective projection matrix
glMatrixMode(GL_MODELVIEW); //specify which matrix is the current matrix,matrix that represents your camera (position, pointing, and up vector).
glutMainLoop();
return 1;
}
[...] now it looks like it's a triangular prism
Of course, a hexagon has 6 sides, but in the function hexagonalPrism you only draw 3 quads for the sides and 2 triangles for the top and the bottom.
Define the 6 points for the corner points of the Hexagon:
x: 0.866, 0.0, -0.866, -0.866, 0.0, 0.866
y: 0.5, 1.0, 0.5, -0.5, -1.0, -0.5
Use the point to draw the 6 quads for the sides and the a the polygon for the top and the bottom. e.g.:
void hexagonalPrism()
{
float x[] = { 0.866f, 0.0f, -0.866f, -0.866f, 0.0f, 0.866f };
float y[] = { 0.5f, 1.0f, 0.5f, -0.5f, -1.0f, -0.5f };
glBegin(GL_QUADS);
for (int i1 = 0; i1 < 6; ++i1)
{
glColor4f(
i1 < 2 || i1 > 4 ? 1.0f : 0.0f,
i1 > 0 && i1 < 5 ? 1.0f : 0.0f,
i1 > 2 ? 1.0f : 0.0f,
1.0f
);
int i2 = (i1 + 1) % 6;
glVertex3f(x[i1], 0.0f, y[i1]);
glVertex3f(x[i2], 0.0f, y[i2]);
glVertex3f(x[i2], 1.0f, y[i2]);
glVertex3f(x[i1], 1.0f, y[i1]);
}
glEnd();
glColor4f( 1, 1, 1, 1 );
glBegin(GL_POLYGON);
for (int i = 0; i < 6; ++i)
glVertex3f(x[i], 0.0f, y[i]);
glEnd();
glBegin(GL_POLYGON);
for (int i = 0; i < 6; ++i)
glVertex3f(x[i], 1.0f, y[i]);
glEnd();
}
Maybe, the problem is here:
if (hexagonalPrism) // should be if(draw_prism)
hexagonalPrism();

3D Cube Drawing, Only One Side Is Always On Top

I was working with OpenGL C++ drawing shapes, specifically cubes. In my current project, I managed to draw a cube correctly, but only the side of the cube that gets drawn last doesn't go transparent when the camera is directly on it. The first two sides of the cube go completely transparent when viewed head-on. Is there a way to fix this? Here is the picture. As you can see, the first two sides don't get displayed. Here is my code:
Main.cpp:
#include "Render.h"
#include <stdlib.h>
int screenHeight = 500;
int screenWidth = 500;
int screenFPS = 60;
void MainLoop(int val);
int main(int argc, char* args[])
{
glutInit(&argc, args);
glutInitDisplayMode(GLUT_DOUBLE);
glutInitWindowSize(screenWidth, screenHeight);
glutInitWindowPosition(350, 80);
glutCreateWindow("Cube");
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
//glOrtho(0.0f, screenWidth, screenHeight, 0.0f, 0.0f, 1.0f);
gluPerspective(40, 1, 0.5, 20);
glutDisplayFunc(Render);
glViewport(0, 0, screenWidth, screenHeight);
glutKeyboardFunc(HandleKeys);
glutIdleFunc(Animation);
glutTimerFunc(1000 / screenFPS, MainLoop, 0);
glutMainLoop();
return 0;
}
void MainLoop(int val)
{
Render();
glutTimerFunc( 1000 / screenFPS, MainLoop, val );
}
Render.cpp:
#include "Render.h"
#include <iostream>
#include <stdlib.h>
#include <windows.h>
GLfloat xRot, yRot, zRot;
void Render()
{
std::cout << xRot << " " << yRot << " " << zRot << "\n";
glMatrixMode(GL_MODELVIEW);
glClear(GL_COLOR_BUFFER_BIT);
glLoadIdentity();
glTranslatef(0.0,0.0,-10.5);
glRotatef(yRot, 1.0, 0.0, 0.0);
glRotatef(yRot, 0.0, 1.0, 0.0);
glRotatef(zRot, 0.0, 0.0, 1.0);
glBegin(GL_QUADS);
glColor4f(0.0f, 1.0f, 0.0f, 1.0f);
glVertex3f( 1.0f, 1.0f,-1.0f);
glVertex3f(-1.0f, 1.0f,-1.0f);
glVertex3f(-1.0f, 1.0f, 1.0f);
glVertex3f( 1.0f, 1.0f, 1.0f);
glColor4f(1.0f, 0.5f, 0.0f, 1.0f);
glVertex3f( 1.0f,-1.0f, 1.0f);
glVertex3f(-1.0f,-1.0f, 1.0f);
glVertex3f(-1.0f,-1.0f,-1.0f);
glVertex3f( 1.0f,-1.0f,-1.0f);
glColor4f(1.0f, 0.0f, 0.0f, 1.0f);
glVertex3f( 1.0f, 1.0f, 1.0f);
glVertex3f(-1.0f, 1.0f, 1.0f);
glVertex3f(-1.0f,-1.0f, 1.0f);
glVertex3f( 1.0f,-1.0f, 1.0f);
glColor4f(1.0f, 1.0f, 0.0f, 1.0f);
glVertex3f( 1.0f,-1.0f,-1.0f);
glVertex3f(-1.0f,-1.0f,-1.0f);
glVertex3f(-1.0f, 1.0f,-1.0f);
glVertex3f( 1.0f, 1.0f,-1.0f);
glColor4f(0.0f, 0.0f, 1.0f, 1.0f);
glVertex3f(-1.0f, 1.0f, 1.0f);
glVertex3f(-1.0f, 1.0f,-1.0f);
glVertex3f(-1.0f,-1.0f,-1.0f);
glVertex3f(-1.0f,-1.0f, 1.0f);
glColor4f(1.0f, 0.0f, 1.0f, 1.0f);
glVertex3f( 1.0f, 1.0f,-1.0f);
glVertex3f( 1.0f, 1.0f, 1.0f);
glVertex3f( 1.0f,-1.0f, 1.0f);
glVertex3f( 1.0f,-1.0f,-1.0f);
glEnd();
glutSwapBuffers();
}
void Animation()
{
yRot += 0.03;
xRot += 0.08;
Render();
}
void HandleKeys(unsigned char key, int x, int y)
{
if(key == 27)
exit(0);
else if(key == 'w')
yRot += 0.55;
else if(key == 'a')
xRot -= 0.55;
else if(key == 's')
yRot -= 0.55;
else if(key == 'd')
xRot += 0.55;
}
Render.h
#include "GLLib.h"
extern int screenHeight;
extern int screenWidth;
extern int screenFPS;
void Render();
void Animation();
void HandleKeys(unsigned char key, int x, int y);
And finally my librarys, GLLib.h:
#ifndef GLLIB_H
#define GLLIB_H
#include <GL/freeglut.h>
#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>
#endif
Chances are that all sides are drawn just fine. The problem is that you don't have a depth buffer. Therefore, everything that is drawn replaces what was drawn previously, no matter if it's in front or behind the previously drawn geometry.
To use a depth buffer, you have to request it during initialization:
glutInitDisplayMode(GLUT_DOUBLE | GLUT_DEPTH);
and enable depth testing before you start rendering:
glEnable(GL_DEPTH_TEST);
Then, at the start of rendering each frame, you need to clear the depth buffer in addition to the color buffer:
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
This will make sure that the front most faces are visible, and the faces behind them are hidden, independent of the drawing order.

C++ and GLUT smooth movement

I am new at using graphics with C++ and I have the following code from this
tutorial
here is the code
#include <windows.h>
#ifdef __APPLE__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif
#include <stdlib.h>
#include <math.h>
float angle = 0.0f;
float lx = 0.0f, lz = -1.0f;
float x = 0.0f, z = 5.0f;
float deltaAngle = 0.0f;
float deltaMove = 0;
void drawSnowMan(){
glColor3f(1.0f, 1.0f, 1.0f);
glTranslatef(0.0f, 0.75f, 0.0f);
glutSolidSphere(0.75f, 20, 20);
glTranslatef(0.0f, 1.0f, 0.0f);
glutSolidSphere(0.25f, 20, 20);
glPushMatrix();
glColor3f(0.0f, 0.0f, 0.0f);
glTranslatef(0.5f, 0.10f, 0.18f);
glutSolidSphere(0.05f, 10, 10);
glTranslatef(-0.1f, 0.0f, 0.0f);
glutSolidSphere(0.05f, 10, 10);
glPopMatrix();
glColor3f(1.0f, 0.5f, 0.5f);
glutSolidCone(0.8f, 0.5f, 10, 2);
}
void changeSize(int w, int h){
if(h == 0)
h = 1;
float ratio = 1.0*w/h;
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glViewport(0,0,w,h);
gluPerspective(45.0f, ratio, 0.1f, 100.0f);
glMatrixMode(GL_MODELVIEW);
}
void computePos(float deltaMove){
x += deltaMove * lx * 0.1f;
z += deltaMove * lz * 0.1f;
}
void computeDir(float deltaAngle){
angle += deltaAngle;
lx = sin(angle/75.0);
lz = -cos(angle/75.0);
}
void pressKey(int key, int xx, int yy){
switch(key){
case GLUT_KEY_LEFT: deltaAngle = -0.5f; break;
case GLUT_KEY_RIGHT: deltaAngle = 0.5; break;
case GLUT_KEY_UP: deltaMove = 0.5f; break;
case GLUT_KEY_DOWN: deltaMove = -0.5f; break;
}
}
void relaseKey(int key, int x, int y){
switch(key){
case GLUT_KEY_LEFT:
case GLUT_KEY_RIGHT: deltaAngle = 0.0f; break;
case GLUT_KEY_UP:
case GLUT_KEY_DOWN: deltaMove = 0; break;
}
}
void renderScene(void){
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
if(deltaMove)
computePos(deltaMove);
if(deltaAngle)
computeDir(deltaAngle);
gluLookAt( x, 1.0f, z,
x+lx, 1.0f, z+lz,
0.0f, 1.0f, 0.0f
);
glColor3f(0.9f, 0.9f, 0.9f);
glBegin(GL_QUADS);
glVertex3f(-100.0f, 0.0f, -100.0f);
glVertex3f(-100.0f, 0.0f, 100.0f);
glVertex3f(100.0f, 0.0f, 100.0f);
glVertex3f(100.0f, 0.0f, -100.0f);
glEnd();
angle += 0.1f;
for(int i = -3; i < 3; i++){
for(int j = -3; j < 3; j++){
glPushMatrix();
glTranslatef(i*10.0,0, j*10.0);
drawSnowMan();
glPopMatrix();
}
}
glutSwapBuffers();
}
int main(int argc, char *argv[])
{
glutInit(&argc, argv);
glutInitWindowSize(320,320);
glutInitWindowPosition(100,100);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
glutCreateWindow("Lighthouse 3D");
glutDisplayFunc(renderScene);
glutReshapeFunc(changeSize);
glutIdleFunc(renderScene);
glutSpecialFunc(pressKey);
glutIgnoreKeyRepeat(1);
glutSpecialUpFunc(relaseKey);
glEnable(GL_DEPTH_TEST);
glutMainLoop();
return 1;
}
My problem is the following, when i try to turn to the left and i keep the left key pressed everything works perfectly fine. When i try to hit the left once the action is not smooth at all. In some cases if the button stroke is too fast it even turns to the opposite direction!
I assume you mean keyboard instead of mouse, in which case to have a "smoother" and "slower" feel you need to adjust your deltaAngle values, which might be too high.
This is only a temporary fix, since those values may affect other machines in different ways - some may be faster, some may be slower. You need to calculate the host machine's FPS in your render loop and multiply your delta values with it, to have the same performance on every computer. This is called time-based movement and is an essential feature of every modern graphics application.
This is exactly what is happening in the following tutorial, when a dot is moving too fast on the screen.
http://lazyfoo.net/SDL_tutorials/lesson32/index.php
A glutIdleFunc() will eat all your battery/CPU/GPU, use a glutTimerFunc() instead to redraw on a predictable, sane schedule.
Accumulate your input state between frames and apply it in your glutTimerFunc() instead of trying to do it right in your keyup/keydown callbacks.
No need for a glutResizeFunc(), do all that just before your draw.
You're using C++ so you should use the C++ versions of C headers, like <cmath> instead of <math.h>.
All together:
#include <GL/glut.h>
#include <cmath>
#include <map>
std::map< int, bool > keys;
void pressKey(int key, int xx, int yy)
{
keys[ key ] = true;
}
void relaseKey(int key, int x, int y)
{
keys[ key ] = false;
}
float angle = 0.0f;
float lx = 0.0f, lz = -1.0f;
float x = 0.0f, z = 5.0f;
void update()
{
const float angleStep = 0.5f;
if( keys[ GLUT_KEY_LEFT ] ) angle -= angleStep;
if( keys[ GLUT_KEY_RIGHT ] ) angle += angleStep;
const float moveStep = 0.5f;
float move = 0.0f;
if( keys[ GLUT_KEY_DOWN ] ) move -= moveStep;
if( keys[ GLUT_KEY_UP ] ) move += moveStep;
x += move * lx * 0.1f;
z += move * lz * 0.1f;
lx = sin(angle/75.0);
lz = -cos(angle/75.0);
}
void drawSnowMan()
{
glColor3f(1.0f, 1.0f, 1.0f);
glTranslatef(0.0f, 0.75f, 0.0f);
glutSolidSphere(0.75f, 20, 20);
glTranslatef(0.0f, 1.0f, 0.0f);
glutSolidSphere(0.25f, 20, 20);
glPushMatrix();
glColor3f(0.0f, 0.0f, 0.0f);
glTranslatef(0.5f, 0.10f, 0.18f);
glutSolidSphere(0.05f, 10, 10);
glTranslatef(-0.1f, 0.0f, 0.0f);
glutSolidSphere(0.05f, 10, 10);
glPopMatrix();
glColor3f(1.0f, 0.5f, 0.5f);
glutSolidCone(0.8f, 0.5f, 10, 2);
}
void renderScene(void)
{
glEnable(GL_DEPTH_TEST);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
const double w = glutGet( GLUT_WINDOW_WIDTH );
const double h = glutGet( GLUT_WINDOW_HEIGHT );
gluPerspective(45.0f, w / h, 0.1f, 100.0f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt
(
x, 1.0f, z,
x+lx, 1.0f, z+lz,
0.0f, 1.0f, 0.0f
);
glColor3f(0.9f, 0.9f, 0.9f);
glBegin(GL_QUADS);
glVertex3f(-100.0f, 0.0f, -100.0f);
glVertex3f(-100.0f, 0.0f, 100.0f);
glVertex3f(100.0f, 0.0f, 100.0f);
glVertex3f(100.0f, 0.0f, -100.0f);
glEnd();
for(int i = -3; i < 3; i++)
{
for(int j = -3; j < 3; j++)
{
glPushMatrix();
glTranslatef(i*10.0,0, j*10.0);
drawSnowMan();
glPopMatrix();
}
}
glutSwapBuffers();
}
void timer( int value )
{
update();
glutTimerFunc( 16, timer, 0 );
glutPostRedisplay();
}
int main(int argc, char *argv[])
{
glutInit(&argc, argv);
glutInitWindowSize(320,320);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
glutCreateWindow("Lighthouse 3D");
glutDisplayFunc(renderScene);
glutSpecialFunc(pressKey);
glutSpecialUpFunc(relaseKey);
glutTimerFunc( 0, timer, 0 );
glutMainLoop();
return 1;
}

Orbiting sphere should cast spot light on central cube

I'm writing a program that draws a rotating cube (with texture) in the middle of the screen followed by a small yellow sphere that orbits around the cube. The idea is to make the sphere as a spot light source that illuminates the cube.
Here is the problem: as you can see in the images below, I'm failing to achieve the spot light effect. It seems that the entire cube gets lighted:
I'm setting GL_SPOT_DIRECTION to be the cube position. I didn't set surface normals because I'm struggling to understand how to compute them for the cube, and I'm not sure a simple graphic application like this really requires it.
I'm sharing the code below:
main.cpp:
#include <QApplication>
#include "glwidget.h"
int main(int argc, char* argv[])
{
QApplication app(argc, argv);
GLWidget gl_widget;
gl_widget.show();
return app.exec();
}
GLWidget.h:
#pragma once
#include <QGLWidget>
#include <QImage>
class GLWidget : public QGLWidget
{
Q_OBJECT
public:
explicit GLWidget(QWidget* parent = 0);
virtual ~GLWidget();
void _draw_texture_cube(int w, int h);
void _draw_light();
/* OpenGL initialization, viewport resizing, and painting */
void initializeGL();
void paintGL();
void resizeGL( int width, int height);
/* enable the user to interact directly with the scene using the keyboard */
void keyPressEvent(QKeyEvent *e);
private:
int _width;
int _height;
QImage* _img;
GLuint _texture;
float xrot;
float yrot;
float zrot;
bool _light_on;
bool _must_rotate;
bool _pause_light;
GLfloat _light_pos[3];
GLfloat _cube_pos[3];
GLUquadricObj* _quadratic;
protected slots:
void _tick();
};
GLWidget.cpp:
#include "GLWidget.h"
#include <iostream>
#include <QKeyEvent>
#include <QTimer>
#include <cmath>
#define LIGHT_MOVEMENT_SPEED 20.0f // Degrees per second
#define pi 3.141592654f
GLWidget::GLWidget(QWidget *parent)
: QGLWidget(parent), _img(NULL), _light_on(true), _must_rotate(true),
_pause_light(false), _quadratic(NULL)
{
_width = 0;
_height = 0;
_texture = 0;
xrot = 0.f;
yrot = 0.f;
zrot = 0.f;
// Set central cube position
_cube_pos[0] = 0.0f;
_cube_pos[1] = 0.0f;
_cube_pos[2] = -7.0f;
// Set light position
_light_pos[0] = 0.5f;
_light_pos[1] = 0.5f;
_light_pos[2] = -7.0f;
}
GLWidget::~GLWidget()
{
if (_img)
delete _img;
glDeleteTextures(1, &_texture);
}
void GLWidget::_tick()
{
update(); // triggers paintGL()
QTimer::singleShot(33, this, SLOT(_tick()));
}
void GLWidget::initializeGL()
{
std::cout << "GLWidget::initializeGL" << std::endl;
glClearColor(0.0f, 0.0f, 0.0f, 1.0f); // Black Background
glEnable(GL_CULL_FACE);
/* Load bitmap */
glEnable(GL_TEXTURE_RECTANGLE_ARB);
glPixelStorei (GL_UNPACK_ALIGNMENT, 1);
if (!_img)
{
std::cout << "GLWidget::paintGL: loading image" << std::endl;
QImage tmp(":/crate.jpg");
if (tmp.isNull())
{
std::cout << "GLWidget::paintGL: !!! Failed QImage #1" << std::endl;
return;
}
_img = new QImage(QGLWidget::convertToGLFormat(tmp));
}
/* Convert bitmap into texture */
// Create The Texture
glGenTextures(1, &_texture);
// Typical Texture Generation Using Data From The Bitmap
glBindTexture(GL_TEXTURE_RECTANGLE_ARB, _texture);
// Generate The Texture
glTexImage2D(GL_TEXTURE_RECTANGLE_ARB, 0,
GL_RGBA, _img->width(), _img->height(), 0,
GL_RGBA, GL_UNSIGNED_BYTE, _img->bits());
if (glGetError() != GL_NO_ERROR)
{
std::cout << "GLWidget::paintGL: !!! Failed glTexImage2D" << std::endl;
return;
}
/* Setup lighting */
glShadeModel(GL_SMOOTH); //Smooth color shading
// Light properties
GLfloat AmbientLight[4] = {0.2, 0.2, 0.2, 1.0};
GLfloat DiffuseLight[4] = {0.8, 0.8, 0.8, 1.0}; // color
GLfloat SpecularLight[4] = {1.0, 1.0, 1.0, 1.0}; // bright
GLfloat SpecRef[] = {0.7f, 0.7f, 0.7f, 1.0f};
GLubyte Shine = 60.0;
//glLightModelfv(GL_LIGHT_MODEL_LOCAL_VIEWER, AmbientLight);
glLightfv(GL_LIGHT0, GL_AMBIENT, AmbientLight);
glLightfv(GL_LIGHT0, GL_DIFFUSE, DiffuseLight);
glLightfv(GL_LIGHT0, GL_SPECULAR, SpecularLight);
glLightfv(GL_LIGHT0, GL_POSITION, _light_pos);
glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE);
glMaterialfv(GL_FRONT, GL_SPECULAR, SpecRef); // refletância do material
glMaterialf(GL_FRONT, GL_SHININESS, Shine); // concentração do brilho
glLightModeli(GL_LIGHT_MODEL_TWO_SIDE, 0);
//glColorMaterial(GL_FRONT,GL_DIFFUSE);
glEnable(GL_COLOR_MATERIAL);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glEnable(GL_DEPTH_TEST);
// Sphere
_quadratic = gluNewQuadric(); // Create A Pointer To The Quadric Object
gluQuadricNormals(_quadratic, GLU_SMOOTH); // Create Smooth Normals
gluQuadricTexture(_quadratic, GL_TRUE); // Create Texture Coords
/* Start the timer */
_tick();
}
/* Draw the central cube with texture
*/
void GLWidget::_draw_texture_cube(int w, int h)
{
glPushMatrix();
glTranslatef(_cube_pos[0], _cube_pos[1], _cube_pos[2]);
glRotatef ( xrot, 1.0, 0.0, 0.0 );
glRotatef ( yrot, 0.0, 1.0, 0.0 );
glRotatef ( zrot, 0.0, 0.0, 1.0 );
glColor3f(1.0f, 1.0f, 1.0f);
glBegin(GL_QUADS); // Draw A Cube
// Front Face
glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f, 1.0f);
glTexCoord2f(w, 0.0f); glVertex3f( 1.0f, -1.0f, 1.0f);
glTexCoord2f(w, h); glVertex3f( 1.0f, 1.0f, 1.0f);
glTexCoord2f(0.0f, h); glVertex3f(-1.0f, 1.0f, 1.0f);
// Back Face
glTexCoord2f(w, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f);
glTexCoord2f(w, h); glVertex3f(-1.0f, 1.0f, -1.0f);
glTexCoord2f(0.0f, h); glVertex3f( 1.0f, 1.0f, -1.0f);
glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f, -1.0f);
// Top Face
glTexCoord2f(0.0f, h); glVertex3f(-1.0f, 1.0f, -1.0f);
glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, 1.0f, 1.0f);
glTexCoord2f(w, 0.0f); glVertex3f( 1.0f, 1.0f, 1.0f);
glTexCoord2f(w, h); glVertex3f( 1.0f, 1.0f, -1.0f);
// Bottom Face
glTexCoord2f(w, h); glVertex3f(-1.0f, -1.0f, -1.0f);
glTexCoord2f(0.0f, h); glVertex3f( 1.0f, -1.0f, -1.0f);
glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f, 1.0f);
glTexCoord2f(w, 0.0f); glVertex3f(-1.0f, -1.0f, 1.0f);
// Right face
glTexCoord2f(w, 0.0f); glVertex3f( 1.0f, -1.0f, -1.0f);
glTexCoord2f(w, h); glVertex3f( 1.0f, 1.0f, -1.0f);
glTexCoord2f(0.0f, _img->height()); glVertex3f( 1.0f, 1.0f, 1.0f);
glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f, 1.0f);
// Left Face
glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f);
glTexCoord2f(w, 0.0f); glVertex3f(-1.0f, -1.0f, 1.0f);
glTexCoord2f(w, h); glVertex3f(-1.0f, 1.0f, 1.0f);
glTexCoord2f(0.0f, h); glVertex3f(-1.0f, 1.0f, -1.0f);
glEnd();
glPopMatrix();
if (_must_rotate)
{
xrot += 0.6f;
yrot += 0.4f;
zrot += 0.8f;
}
}
/* Draw light source and light model (sphere)
*/
void GLWidget::_draw_light()
{
if (_light_on)
{
glEnable(GL_LIGHT0); // enable lights that we use
}
else
{
glDisable(GL_LIGHT0);
}
static float light_angle = 25.0f;
if (!_pause_light) // stop moving the light source
{
light_angle += LIGHT_MOVEMENT_SPEED * 0.1;
if (light_angle > 360.0f)
light_angle -= 360.0f;
}
/* Set light source position */
_light_pos[0] = 4.0f * (float) cos(light_angle * pi / 180.0f);
_light_pos[1] = 4.0f * (float) sin(light_angle * pi / 180.0f);
_light_pos[2] = -7;
glLightfv(GL_LIGHT0, GL_POSITION, _light_pos);
GLfloat SpotDir[] = {_cube_pos[0], _cube_pos[1], _cube_pos[2], 0.0 };
glLightfv(GL_LIGHT0, GL_SPOT_DIRECTION, SpotDir);
glLightf(GL_LIGHT0, GL_SPOT_CUTOFF, 150.0);
glLightf(GL_LIGHT0, GL_SPOT_EXPONENT, 15.0);
/* Set the light model position to be the same as the light source */
glPushMatrix();
glTranslatef(_light_pos[0], _light_pos[1], _light_pos[2]);
glColor3ub(255, 255, 0); // yellow
gluSphere(_quadratic, 0.2f, 32, 32); // draw sphere
glPopMatrix();
}
void GLWidget::paintGL()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear Screen And Depth Buffer
glMatrixMode ( GL_MODELVIEW ); // Select The Model View Matrix
glLoadIdentity(); // Reset The Current Modelview Matrix
/* Draw central cube */
glEnable(GL_TEXTURE_RECTANGLE_ARB);
glBindTexture(GL_TEXTURE_RECTANGLE_ARB, _texture); // Select Our Texture
_draw_texture_cube(_img->width(), _img->height());
glDisable(GL_TEXTURE_RECTANGLE_ARB);
/* Draw light source and light model*/
_draw_light();
}
void GLWidget::resizeGL( int w, int h)
{
_width = w;
_height = h;
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION); // Select The Projection Matrix
glLoadIdentity(); // Reset The Projection Matrix
if (h == 0) // Calculate The Aspect Ratio Of The Window
gluPerspective ( 60, ( float ) w, 0.4, 500.0 );
else
gluPerspective ( 60, ( float ) w / ( float ) h, 0.4, 500.0 );
glMatrixMode ( GL_MODELVIEW ); // Select The Model View Matrix
glLoadIdentity ( ); // Reset The Model View Matrix
gluLookAt(0.0, 0.0, 2.0, // eye
0.0, 0.0, 0.0, // center
0.0, 1.0, 0.0); // up
}
void GLWidget::keyPressEvent(QKeyEvent *e)
{
switch (e->key())
{
case Qt::Key_L:
if (_light_on)
_light_on = false;
else
_light_on = true;
break;
case Qt::Key_P:
if (_pause_light)
_pause_light = false;
else
_pause_light = true;
break;
case Qt::Key_R:
if (_must_rotate)
_must_rotate = false;
else
_must_rotate = true;
break;
default:
break;
}
}
Lighting.pro:
QT += core gui opengl
SOURCES += \
GLWidget.cpp \
main.cpp
HEADERS += \
GLWidget.h
RESOURCES += \
resource.qrc
What needs to be changed in this application in order to achieve the desired effect?
You do not specify any normals for your cube faces. As OpenGL is a state machine, it will use the default surface normal for all vertices, hence all of your faces. As the normal vector is crucial for the lighting, all of your faces will be lit almost identical (vertex postions still are different, but the effect is weak).
You should also be aware that the fixed function lighting of OpenGL is done per vertex. If you really want to see a good spotlight on the cuve, you would either need to tessalate it so more vertices are used where the lighting equation is actually evaluated, or use shaders for per-fragment lighting.

OpenGL SkyBox not showing

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;
}
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.
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.