progs/demos/spectex.c

   1
   2 /*
   3  * GLUT demonstration of texturing with specular highlights.
   4  *
   5  * When drawing a lit, textured surface one usually wants the specular
   6  * highlight to override the texture colors.  However, OpenGL applies
   7  * texturing after lighting so the specular highlight is modulated by
   8  * the texture.
   9  *
  10  * The solution here shown here is a two-pass algorithm:
  11  *  1. Draw the textured surface without specular lighting.
  12  *  2. Enable blending to add the next pass:
  13  *  3. Redraw the surface with a matte white material and only the
  14  *     specular components of light sources enabled.
  15  *
  16  * Brian Paul  February 1997
  17  */
  18
  19 #include <stdio.h>
  20 #include <stdlib.h>
  21 #include <math.h>
  22 #include <GL/glut.h>
  23
  24
  25 static GLUquadricObj *Quadric;
  26 static GLuint Sphere;
  27 static GLfloat LightPos[4] = {10.0, 10.0, 10.0, 1.0};
  28 static GLfloat Delta = 20.0;
  29 static GLint Mode = 4;
  30
  31 /*static GLfloat Blue[4] = {0.0, 0.0, 1.0, 1.0};*/
  32 /*static GLfloat Gray[4] = {0.5, 0.5, 0.5, 1.0};*/
  33 static GLfloat Black[4] = {0.0, 0.0, 0.0, 1.0};
  34 static GLfloat White[4] = {1.0, 1.0, 1.0, 1.0};
  35
  36 static GLboolean smooth = 1;
  37
  38 static void
  39 Idle(void)
  40 {
  41    static double t0 = -1.;
  42    double dt, t = glutGet(GLUT_ELAPSED_TIME) / 1000.0;;
  43    if (t0 < 0.0)
  44       t0 = t;
  45    dt = t - t0;
  46    t0 = t;
  47    LightPos[0] += Delta * dt;
  48    if (LightPos[0]>15.0 || LightPos[0]<-15.0)
  49       Delta = -Delta;
  50
  51    glutPostRedisplay();
  52 }
  53
  54
  55 static void Display( void )
  56 {
  57    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
  58
  59    glLightfv(GL_LIGHT0, GL_POSITION, LightPos);
  60
  61    glPushMatrix();
  62    glRotatef(90.0, 1.0, 0.0, 0.0);
  63
  64    if (Mode==0) {
  65       /* Typical method: diffuse + specular + texture */
  66       glEnable(GL_TEXTURE_2D);
  67       glLightfv(GL_LIGHT0, GL_DIFFUSE, White);  /* enable diffuse */
  68       glLightfv(GL_LIGHT0, GL_SPECULAR, White);  /* enable specular */
  69 #ifdef GL_VERSION_1_2
  70       glLightModeli(GL_LIGHT_MODEL_COLOR_CONTROL, GL_SINGLE_COLOR);
  71 #endif
  72       glCallList(Sphere);
  73    }
  74    else if (Mode==1) {
  75       /* just specular highlight */
  76       glDisable(GL_TEXTURE_2D);
  77       glLightfv(GL_LIGHT0, GL_DIFFUSE, Black);  /* disable diffuse */
  78       glLightfv(GL_LIGHT0, GL_SPECULAR, White);  /* enable specular */
  79 #ifdef GL_VERSION_1_2
  80       glLightModeli(GL_LIGHT_MODEL_COLOR_CONTROL, GL_SINGLE_COLOR);
  81 #endif
  82       glCallList(Sphere);
  83    }
  84    else if (Mode==2) {
  85       /* diffuse textured */
  86       glEnable(GL_TEXTURE_2D);
  87       glLightfv(GL_LIGHT0, GL_DIFFUSE, White);  /* enable diffuse */
  88       glLightfv(GL_LIGHT0, GL_SPECULAR, Black);  /* disable specular */
  89 #ifdef GL_VERSION_1_2
  90       glLightModeli(GL_LIGHT_MODEL_COLOR_CONTROL, GL_SINGLE_COLOR);
  91 #endif
  92       glCallList(Sphere);
  93    }
  94    else if (Mode==3) {
  95       /* 2-pass: diffuse textured then add specular highlight*/
  96       glEnable(GL_TEXTURE_2D);
  97       glLightfv(GL_LIGHT0, GL_DIFFUSE, White);  /* enable diffuse */
  98       glLightfv(GL_LIGHT0, GL_SPECULAR, Black);  /* disable specular */
  99 #ifdef GL_VERSION_1_2
 100       glLightModeli(GL_LIGHT_MODEL_COLOR_CONTROL, GL_SINGLE_COLOR);
 101 #endif
 102       glCallList(Sphere);
 103       /* specular highlight */
 104       glDepthFunc(GL_EQUAL);  /* redraw same pixels */
 105       glDisable(GL_TEXTURE_2D);
 106       glEnable(GL_BLEND);  /* add */
 107       glLightfv(GL_LIGHT0, GL_DIFFUSE, Black);  /* disable diffuse */
 108       glLightfv(GL_LIGHT0, GL_SPECULAR, White);  /* enable specular */
 109       glCallList(Sphere);
 110       glDepthFunc(GL_LESS);
 111       glDisable(GL_BLEND);
 112    }
 113    else if (Mode==4) {
 114       /* OpenGL 1.2's separate diffuse and specular color */
 115       glEnable(GL_TEXTURE_2D);
 116       glLightfv(GL_LIGHT0, GL_DIFFUSE, White);  /* enable diffuse */
 117       glLightfv(GL_LIGHT0, GL_SPECULAR, White);  /* enable specular */
 118 #ifdef GL_VERSION_1_2
 119       glLightModeli(GL_LIGHT_MODEL_COLOR_CONTROL, GL_SEPARATE_SPECULAR_COLOR);
 120 #endif
 121       glCallList(Sphere);
 122    }
 123
 124    glPopMatrix();
 125
 126    glutSwapBuffers();
 127 }
 128
 129
 130 static void Reshape( int width, int height )
 131 {
 132    glViewport( 0, 0, width, height );
 133    glMatrixMode( GL_PROJECTION );
 134    glLoadIdentity();
 135    glFrustum( -1.0, 1.0, -1.0, 1.0, 5.0, 25.0 );
 136    glMatrixMode( GL_MODELVIEW );
 137    glLoadIdentity();
 138    glTranslatef( 0.0, 0.0, -12.0 );
 139 }
 140
 141
 142 static void Key( unsigned char key, int x, int y )
 143 {
 144    (void) x;
 145    (void) y;
 146    switch (key) {
 147    case 27:
 148       exit(0);
 149       break;
 150    case 's':
 151       smooth = !smooth;
 152       if (smooth)
 153          glShadeModel(GL_SMOOTH);
 154       else
 155          glShadeModel(GL_FLAT);
 156       break;
 157    }
 158    glutPostRedisplay();
 159 }
 160
 161
 162 static void SpecialKey( int key, int x, int y )
 163 {
 164    (void) x;
 165    (void) y;
 166    switch (key) {
 167       case GLUT_KEY_UP:
 168          break;
 169       case GLUT_KEY_DOWN:
 170          break;
 171    }
 172    glutPostRedisplay();
 173 }
 174
 175
 176 static void Init( void )
 177 {
 178    int i, j;
 179    GLubyte texImage[64][64][3];
 180
 181    glEnable(GL_LIGHTING);
 182    glEnable(GL_LIGHT0);
 183    glLightModeli(GL_LIGHT_MODEL_TWO_SIDE, 0);
 184    glLightModelfv(GL_LIGHT_MODEL_AMBIENT, Black);
 185
 186    glShadeModel(GL_SMOOTH);
 187
 188    glMaterialfv(GL_FRONT, GL_DIFFUSE, White);
 189    glMaterialfv(GL_FRONT, GL_SPECULAR, White);
 190    glMaterialf(GL_FRONT, GL_SHININESS, 20.0);
 191
 192    /* Actually, these are set again later */
 193    glLightfv(GL_LIGHT0, GL_DIFFUSE, White);
 194    glLightfv(GL_LIGHT0, GL_SPECULAR, White);
 195
 196    Quadric = gluNewQuadric();
 197    gluQuadricTexture( Quadric, GL_TRUE );
 198
 199    Sphere= glGenLists(1);
 200    glNewList( Sphere, GL_COMPILE );
 201    gluSphere( Quadric, 1.0, 24, 24 );
 202    glEndList();
 203
 204    glEnable(GL_DEPTH_TEST);
 205    glEnable(GL_CULL_FACE);
 206
 207    for (i=0;i<64;i++) {
 208       for (j=0;j<64;j++) {
 209          int k = ((i>>3)&1) ^ ((j>>3)&1);
 210          texImage[i][j][0] = 255*k;
 211          texImage[i][j][1] = 255*(1-k);
 212          texImage[i][j][2] = 0;
 213       }
 214    }
 215
 216    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
 217    glTexImage2D( GL_TEXTURE_2D,
 218                  0,
 219                  3,
 220                  64, 64,
 221                  0,
 222                  GL_RGB, GL_UNSIGNED_BYTE,
 223                  texImage );
 224    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
 225    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
 226    glEnable(GL_TEXTURE_2D);
 227
 228    glBlendFunc(GL_ONE, GL_ONE);
 229 }
 230
 231
 232 static void ModeMenu(int entry)
 233 {
 234    if (entry==99)
 235       exit(0);
 236    Mode = entry;
 237 }
 238
 239
 240 int main( int argc, char *argv[] )
 241 {
 242
 243    glutInit( &argc, argv );
 244    glutInitWindowPosition( 0, 0 );
 245    glutInitWindowSize( 300, 300 );
 246
 247    glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH );
 248
 249    glutCreateWindow( "spectex" );
 250
 251    Init();
 252
 253    glutReshapeFunc( Reshape );
 254    glutKeyboardFunc( Key );
 255    glutSpecialFunc( SpecialKey );
 256    glutDisplayFunc( Display );
 257    glutIdleFunc( Idle );
 258
 259    glutCreateMenu( ModeMenu );
 260    glutAddMenuEntry("1-pass lighting + texturing", 0);
 261    glutAddMenuEntry("specular lighting", 1);
 262    glutAddMenuEntry("diffuse lighting + texturing", 2);
 263    glutAddMenuEntry("2-pass lighting + texturing", 3);
 264 #ifdef GL_VERSION_1_2
 265    glutAddMenuEntry("OpenGL 1.2 separate specular", 4);
 266 #endif
 267    glutAddMenuEntry("Quit", 99);
 268    glutAttachMenu(GLUT_RIGHT_BUTTON);
 269
 270    glutMainLoop();
 271    return 0;
 272 }