NeHe OpenGL Lesson 9

//// This code was created by Jeff Molofee '99 (ported to Linux/GLUT by // Richard Campbell '99)//// If you've found this code useful, please let me know.//// Visit me at www.demonews.com/hosted/nehe // (email Richard Campbell at [e-mail])///* Linux#include <GL/glut.h>    // Header File For The GLUT Library #include <GL/gl.h>// Header File For The OpenGL32 Library#include <GL/glu.h>// Header File For The GLu32 Library*/// Mac OS X #include <OpenGL/OpenGL.h>#include <GLUT/GLUT.h>#include <unistd.h>     // Header file for sleeping.#include <stdio.h>      // Header file for standard file i/o.#include <stdlib.h>     // Header file for malloc/free./* number of stars to have */#define STAR_NUM 50/* ascii codes for various special keys */#define ESCAPE 27#define PAGE_UP 73#define PAGE_DOWN 81#define UP_ARROW 72#define DOWN_ARROW 80#define LEFT_ARROW 75#define RIGHT_ARROW 77/* The number of our GLUT window */int window; /* twinkle on/off (1 = on, 0 = off) */int twinkle = 0;typedef struct {         // Star structure    int r, g, b;         // stars' color    GLfloat dist;        // stars' distance from center    GLfloat angle;       // stars' current angle} stars;                 // name is starsstars star[STAR_NUM];    // make 'star' array of STAR_NUM size using info from the structure 'stars'GLfloat zoom = -15.0f;   // viewing distance from stars.GLfloat tilt = 90.0f;    // tilt the viewGLfloat spin;            // spin twinkling starsGLuint loop;             // general loop variableGLuint texture[1];       // storage for one texture;/* Image type - contains height, width, and data */struct Image {    unsigned long sizeX;    unsigned long sizeY;    char *data;};typedef struct Image Image;/* * getint and getshort are help functions to load the bitmap byte by byte on  * SPARC platform (actually, just makes the thing work on platforms of either * endianness, not just Intel's little endian) */static unsigned int getint(fp)     FILE *fp;{  int c, c1, c2, c3;  // get 4 bytes  c = getc(fp);    c1 = getc(fp);    c2 = getc(fp);    c3 = getc(fp);    return ((unsigned int) c) +       (((unsigned int) c1) << 8) +     (((unsigned int) c2) << 16) +    (((unsigned int) c3) << 24);}static unsigned int getshort(fp)     FILE *fp;{  int c, c1;    //get 2 bytes  c = getc(fp);    c1 = getc(fp);  return ((unsigned int) c) + (((unsigned int) c1) << 8);}// quick and dirty bitmap loader...for 24 bit bitmaps with 1 plane only.  // See http://www.dcs.ed.ac.uk/~mxr/gfx/2d/BMP.txt for more info.int ImageLoad(char *filename, Image *image) {    FILE *file;    unsigned long size;                 // size of the image in bytes.    unsigned long i;                    // standard counter.    unsigned short int planes;          // number of planes in image (must be 1)     unsigned short int bpp;             // number of bits per pixel (must be 24)    char temp;                          // used to convert bgr to rgb color.    // make sure the file is there.    if ((file = fopen(filename, "rb"))==NULL) {      printf("File Not Found : %s\n",filename);      return 0;    }        // seek through the bmp header, up to the width/height:    fseek(file, 18, SEEK_CUR);    // No 100% errorchecking anymore!!!    // read the width    image->sizeX = getint (file);    printf("Width of %s: %lu\n", filename, image->sizeX);        // read the height     image->sizeY = getint (file);    printf("Height of %s: %lu\n", filename, image->sizeY);        // calculate the size (assuming 24 bits or 3 bytes per pixel).    size = image->sizeX * image->sizeY * 3;    // read the planes    planes = getshort(file);    if (planes != 1) {printf("Planes from %s is not 1: %u\n", filename, planes);return 0;    }    // read the bpp    bpp = getshort(file);    if (bpp != 24) {      printf("Bpp from %s is not 24: %u\n", filename, bpp);      return 0;    }    // seek past the rest of the bitmap header.    fseek(file, 24, SEEK_CUR);    // read the data.     image->data = (char *) malloc(size);    if (image->data == NULL) {printf("Error allocating memory for color-corrected image data");return 0;    }    if ((i = fread(image->data, size, 1, file)) != 1) {printf("Error reading image data from %s.\n", filename);return 0;    }    for (i=0;i<size;i+=3) { // reverse all of the colors. (bgr -> rgb)temp = image->data[i];image->data[i] = image->data[i+2];image->data[i+2] = temp;    }    // we're done.    return 1;}// Load Bitmaps And Convert To TexturesGLvoid LoadGLTextures(GLvoid) {    // Load Texture    Image *image1;        // allocate space for texture    image1 = (Image *) malloc(sizeof(Image));    if (image1 == NULL) {printf("Error allocating space for image");exit(0);    }    if (!ImageLoad("Data/lesson9/Star.bmp", image1)) {exit(1);    }            // Create Textures    glGenTextures(3, &texture[0]);    // linear filtered texture    glBindTexture(GL_TEXTURE_2D, texture[0]);   // 2d texture (x and y size)    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR); // scale linearly when image bigger than texture    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR); // scale linearly when image smalled than texture    glTexImage2D(GL_TEXTURE_2D, 0, 3, image1->sizeX, image1->sizeY, 0, GL_RGB, GL_UNSIGNED_BYTE, image1->data);};/* A general OpenGL initialization function.  Sets all of the initial parameters. */GLvoid InitGL(GLsizei Width, GLsizei Height)// We call this right after our OpenGL window is created.{    LoadGLTextures();                           // load the textures.    glEnable(GL_TEXTURE_2D);                    // Enable texture mapping.    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    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);    /* setup blending */    glBlendFunc(GL_SRC_ALPHA,GL_ONE);        // Set The Blending Function For Translucency    glEnable(GL_BLEND);                         // Enable Blending    /* set up the stars */    for (loop=0; loop<STAR_NUM; loop++) {star[loop].angle = 0.0f;                // initially no rotation.star[loop].dist = loop * 1.0f / STAR_NUM * 5.0f; // calculate distance form the centerstar[loop].r = rand() % 256;            // random red intensity;star[loop].g = rand() % 256;            // random green intensity;star[loop].b = rand() % 256;            // random blue intensity;    }    }/* The function called when our window is resized (which shouldn't happen, because we're fullscreen) */GLvoid ReSizeGLScene(GLsizei Width, GLsizei Height){    if (Height==0)// Prevent A Divide By Zero If The Window Is Too SmallHeight=1;    glViewport(0, 0, Width, Height);// Reset The Current Viewport And Perspective Transformation    glMatrixMode(GL_PROJECTION);    glLoadIdentity();    gluPerspective(45.0f,(GLfloat)Width/(GLfloat)Height,0.1f,100.0f);    glMatrixMode(GL_MODELVIEW);}/* The main drawing function. */GLvoid DrawGLScene(GLvoid){    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);// Clear The Screen And The Depth Buffer        glBindTexture(GL_TEXTURE_2D, texture[0]);    // pick the texture.    for (loop=0; loop<STAR_NUM; loop++) {        // loop through all the stars.glLoadIdentity();                        // reset the view before we draw each star.glTranslatef(0.0f, 0.0f, zoom);          // zoom into the screen.glRotatef(tilt, 1.0f, 0.0f, 0.0f);       // tilt the view.glRotatef(star[loop].angle, 0.0f, 1.0f, 0.0f); // rotate to the current star's angle.glTranslatef(star[loop].dist, 0.0f, 0.0f); // move forward on the X plane (the star's x plane).glRotatef(-star[loop].angle, 0.0f, 1.0f, 0.0f); // cancel the current star's angle.glRotatef(-tilt, 1.0f, 0.0f, 0.0f);      // cancel the screen tilt.if (twinkle) {                           // twinkling stars enabled ... draw an additional star.    // assign a color using bytes    glColor4ub(star[STAR_NUM - loop].r, star[STAR_NUM - loop].g, star[STAR_NUM - loop].b, 255);    glBegin(GL_QUADS);                   // begin drawing the textured quad.    glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f, 0.0f);    glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f, 0.0f);    glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  1.0f, 0.0f);    glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f, 1.0f, 0.0f);    glEnd();                             // done drawing the textured quad.}// main starglRotatef(spin, 0.0f, 0.0f, 1.0f);       // rotate the star on the z axis.        // Assign A Color Using BytesglColor4ub(star[loop].r,star[loop].g,star[loop].b,255);glBegin(GL_QUADS);// Begin Drawing The Textured QuadglTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f,-1.0f, 0.0f);glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f,-1.0f, 0.0f);glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f, 1.0f, 0.0f);glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f, 1.0f, 0.0f);glEnd();// Done Drawing The Textured Quadspin +=0.01f;                           // used to spin the stars.star[loop].angle += loop * 1.0f / STAR_NUM * 1.0f;    // change star angle.star[loop].dist  -= 0.01f;              // bring back to center.if (star[loop].dist<0.0f) {             // star hit the center    star[loop].dist += 5.0f;            // move 5 units from the center.    star[loop].r = rand() % 256;        // new red color.    star[loop].g = rand() % 256;        // new green color.    star[loop].b = rand() % 256;        // new blue color.}    }       // since this is double buffered, swap the buffers to display what just got drawn.    glutSwapBuffers();}/* The function called whenever a normal key is pressed. */void keyPressed(unsigned char key, int x, int y) {    /* avoid thrashing this procedure */    usleep(100);    switch (key) {        case ESCAPE: // kill everything./* exit the program...normal termination. */exit(1);                   break; // redundant.    case 84:     case 116: // switch the twinkling.printf("T/t pressed; twinkle is: %d\n", twinkle);twinkle = twinkle ? 0 : 1;              // switch the current value of twinkle, between 0 and 1.printf("Twinkle is now: %d\n", twinkle);break;    default:      printf ("Key %d pressed. No action there yet.\n", key);      break;    }}/* The function called whenever a normal key is pressed. */void specialKeyPressed(int key, int x, int y) {    /* avoid thrashing this procedure */    usleep(100);    switch (key) {        case GLUT_KEY_PAGE_UP: // zoom outzoom -= 0.2f;break;        case GLUT_KEY_PAGE_DOWN: // zoom inzoom += 0.2f;break;    case GLUT_KEY_UP: // tilt uptilt -= 0.5f;break;    case GLUT_KEY_DOWN: // tilt downtilt += 0.5f;break;    default:printf ("Special key %d pressed. No action there yet.\n", key);break;    }}int main(int argc, char **argv) {      /* Initialize GLUT state - glut will take any command line arguments that pertain to it or        X Windows - look at its documentation at http://reality.sgi.com/mjk/spec3/spec3.html */      glutInit(&argc, argv);      /* Select type of Display mode:        Double buffer      RGBA color     Depth buffer */    glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH);      /* get a 640 x 480 window */    glutInitWindowSize(640, 480);      /* the window starts at the upper left corner of the screen */    glutInitWindowPosition(0, 0);      /* Open a window */      window = glutCreateWindow("Jeff Molofee's GL Code Tutorial ... NeHe '99");      /* Register the function to do all our OpenGL drawing. */    glutDisplayFunc(&DrawGLScene);      /* Go fullscreen.  This is as soon as possible. */    //glutFullScreen();    /* Even if there are no events, redraw our gl scene. */    glutIdleFunc(&DrawGLScene);     /* Register the function called when our window is resized. */    glutReshapeFunc(&ReSizeGLScene);    /* Register the function called when the keyboard is pressed. */    glutKeyboardFunc(&keyPressed);    /* Register the function called when special keys (arrows, page down, etc) are pressed. */    glutSpecialFunc(&specialKeyPressed);    /* Initialize our window. */    InitGL(640, 480);      /* Start Event Processing Engine */      glutMainLoop();      return 1;}

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clang -o lesson lesson9.c -Wno-deprecated -framework OpenGL -framework GLUT