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 = 1.0;
  29 static GLint Mode = 0;
  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
  37
  38 static void Idle( void )
  39 {
  40    LightPos[0] += Delta;
  41    if (LightPos[0]>15.0)
  42       Delta = -1.0;
  43    else if (LightPos[0]<-15.0)
  44       Delta = 1.0;
  45
  46    glutPostRedisplay();
  47 }
  48
  49
  50 static void Display( void )
  51 {
  52    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
  53
  54    glLightfv(GL_LIGHT0, GL_POSITION, LightPos);
  55
  56    glPushMatrix();
  57    glRotatef(90.0, 1.0, 0.0, 0.0);
  58
  59    if (Mode==0) {
  60       /* Typical method: diffuse + specular + texture */
  61       glEnable(GL_TEXTURE_2D);
  62       glLightfv(GL_LIGHT0, GL_DIFFUSE, White);  /* enable diffuse */
  63       glLightfv(GL_LIGHT0, GL_SPECULAR, White);  /* enable specular */
  64 #ifdef GL_VERSION_1_2
  65       glLightModeli(GL_LIGHT_MODEL_COLOR_CONTROL, GL_SINGLE_COLOR);
  66 #endif
  67       glCallList(Sphere);
  68    }
  69    else if (Mode==1) {
  70       /* just specular highlight */
  71       glDisable(GL_TEXTURE_2D);
  72       glLightfv(GL_LIGHT0, GL_DIFFUSE, Black);  /* disable diffuse */
  73       glLightfv(GL_LIGHT0, GL_SPECULAR, White);  /* enable specular */
  74 #ifdef GL_VERSION_1_2
  75       glLightModeli(GL_LIGHT_MODEL_COLOR_CONTROL, GL_SINGLE_COLOR);
  76 #endif
  77       glCallList(Sphere);
  78    }
  79    else if (Mode==2) {
  80       /* diffuse textured */
  81       glEnable(GL_TEXTURE_2D);
  82       glLightfv(GL_LIGHT0, GL_DIFFUSE, White);  /* enable diffuse */
  83       glLightfv(GL_LIGHT0, GL_SPECULAR, Black);  /* disable specular */
  84 #ifdef GL_VERSION_1_2
  85       glLightModeli(GL_LIGHT_MODEL_COLOR_CONTROL, GL_SINGLE_COLOR);
  86 #endif
  87       glCallList(Sphere);
  88    }
  89    else if (Mode==3) {
  90       /* 2-pass: diffuse textured then add specular highlight*/
  91       glEnable(GL_TEXTURE_2D);
  92       glLightfv(GL_LIGHT0, GL_DIFFUSE, White);  /* enable diffuse */
  93       glLightfv(GL_LIGHT0, GL_SPECULAR, Black);  /* disable specular */
  94 #ifdef GL_VERSION_1_2
  95       glLightModeli(GL_LIGHT_MODEL_COLOR_CONTROL, GL_SINGLE_COLOR);
  96 #endif
  97       glCallList(Sphere);
  98       /* specular highlight */
  99       glDepthFunc(GL_EQUAL);  /* redraw same pixels */
 100       glDisable(GL_TEXTURE_2D);
 101       glEnable(GL_BLEND);  /* add */
 102       glLightfv(GL_LIGHT0, GL_DIFFUSE, Black);  /* disable diffuse */
 103       glLightfv(GL_LIGHT0, GL_SPECULAR, White);  /* enable specular */
 104       glCallList(Sphere);
 105       glDepthFunc(GL_LESS);
 106       glDisable(GL_BLEND);
 107    }
 108    else if (Mode==4) {
 109       /* OpenGL 1.2's separate diffuse and specular color */
 110       glEnable(GL_TEXTURE_2D);
 111       glLightfv(GL_LIGHT0, GL_DIFFUSE, White);  /* enable diffuse */
 112       glLightfv(GL_LIGHT0, GL_SPECULAR, White);  /* enable specular */
 113 #ifdef GL_VERSION_1_2
 114       glLightModeli(GL_LIGHT_MODEL_COLOR_CONTROL, GL_SEPARATE_SPECULAR_COLOR);
 115 #endif
 116       glCallList(Sphere);
 117    }
 118
 119    glPopMatrix();
 120
 121    glutSwapBuffers();
 122 }
 123
 124
 125 static void Reshape( int width, int height )
 126 {
 127    glViewport( 0, 0, width, height );
 128    glMatrixMode( GL_PROJECTION );
 129    glLoadIdentity();
 130    glFrustum( -1.0, 1.0, -1.0, 1.0, 5.0, 25.0 );
 131    glMatrixMode( GL_MODELVIEW );
 132    glLoadIdentity();
 133    glTranslatef( 0.0, 0.0, -12.0 );
 134 }
 135
 136
 137 static void Key( unsigned char key, int x, int y )
 138 {
 139    (void) x;
 140    (void) y;
 141    switch (key) {
 142       case 27:
 143          exit(0);
 144          break;
 145    }
 146    glutPostRedisplay();
 147 }
 148
 149
 150 static void SpecialKey( int key, int x, int y )
 151 {
 152    (void) x;
 153    (void) y;
 154    switch (key) {
 155       case GLUT_KEY_UP:
 156          break;
 157       case GLUT_KEY_DOWN:
 158          break;
 159    }
 160    glutPostRedisplay();
 161 }
 162
 163
 164 static void Init( void )
 165 {
 166    int i, j;
 167    GLubyte texImage[64][64][3];
 168
 169    glEnable(GL_LIGHTING);
 170    glEnable(GL_LIGHT0);
 171    glLightModeli(GL_LIGHT_MODEL_TWO_SIDE, 0);
 172    glLightModelfv(GL_LIGHT_MODEL_AMBIENT, Black);
 173
 174    glMaterialfv(GL_FRONT, GL_DIFFUSE, White);
 175    glMaterialfv(GL_FRONT, GL_SPECULAR, White);
 176    glMaterialf(GL_FRONT, GL_SHININESS, 20.0);
 177
 178    /* Actually, these are set again later */
 179    glLightfv(GL_LIGHT0, GL_DIFFUSE, White);
 180    glLightfv(GL_LIGHT0, GL_SPECULAR, White);
 181
 182    Quadric = gluNewQuadric();
 183    gluQuadricTexture( Quadric, GL_TRUE );
 184
 185    Sphere= glGenLists(1);
 186    glNewList( Sphere, GL_COMPILE );
 187    gluSphere( Quadric, 1.0, 24, 24 );
 188    glEndList();
 189
 190    glEnable(GL_DEPTH_TEST);
 191    glEnable(GL_CULL_FACE);
 192
 193    for (i=0;i<64;i++) {
 194       for (j=0;j<64;j++) {
 195          int k = ((i>>3)&1) ^ ((j>>3)&1);
 196          texImage[i][j][0] = 255*k;
 197          texImage[i][j][1] = 255*(1-k);
 198          texImage[i][j][2] = 0;
 199       }
 200    }
 201
 202    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
 203    glTexImage2D( GL_TEXTURE_2D,
 204                  0,
 205                  3,
 206                  64, 64,
 207                  0,
 208                  GL_RGB, GL_UNSIGNED_BYTE,
 209                  texImage );
 210    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
 211    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
 212    glEnable(GL_TEXTURE_2D);
 213
 214    glBlendFunc(GL_ONE, GL_ONE);
 215 }
 216
 217
 218 static void ModeMenu(int entry)
 219 {
 220    if (entry==99)
 221       exit(0);
 222    Mode = entry;
 223 }
 224
 225
 226 int main( int argc, char *argv[] )
 227 {
 228
 229    glutInit( &argc, argv );
 230    glutInitWindowPosition( 0, 0 );
 231    glutInitWindowSize( 300, 300 );
 232
 233    glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH );
 234
 235    glutCreateWindow( "spectex" );
 236
 237    Init();
 238
 239    glutReshapeFunc( Reshape );
 240    glutKeyboardFunc( Key );
 241    glutSpecialFunc( SpecialKey );
 242    glutDisplayFunc( Display );
 243    glutIdleFunc( Idle );
 244
 245    glutCreateMenu( ModeMenu );
 246    glutAddMenuEntry("1-pass lighting + texturing", 0);
 247    glutAddMenuEntry("specular lighting", 1);
 248    glutAddMenuEntry("diffuse lighting + texturing", 2);
 249    glutAddMenuEntry("2-pass lighting + texturing", 3);
 250 #ifdef GL_VERSION_1_2
 251    glutAddMenuEntry("OpenGL 1.2 separate specular", 4);
 252 #endif
 253    glutAddMenuEntry("Quit", 99);
 254    glutAttachMenu(GLUT_RIGHT_BUTTON);
 255
 256    glutMainLoop();
 257    return 0;
 258 }