progs/demos/spectex.c

   1 /* $Id: spectex.c,v 1.2 2002/04/22 16:03:37 brianp Exp $ */
   2
   3 /*
   4  * GLUT demonstration of texturing with specular highlights.
   5  *
   6  * When drawing a lit, textured surface one usually wants the specular
   7  * highlight to override the texture colors.  However, OpenGL applies
   8  * texturing after lighting so the specular highlight is modulated by
   9  * the texture.
  10  *
  11  * The solution here shown here is a two-pass algorithm:
  12  *  1. Draw the textured surface without specular lighting.
  13  *  2. Enable blending to add the next pass:
  14  *  3. Redraw the surface with a matte white material and only the
  15  *     specular components of light sources enabled.
  16  *
  17  * Brian Paul  February 1997
  18  */
  19
  20 #include <stdio.h>
  21 #include <stdlib.h>
  22 #include <math.h>
  23 #include <GL/glut.h>
  24
  25
  26 static GLUquadricObj *Quadric;
  27 static GLuint Sphere;
  28 static GLfloat LightPos[4] = {10.0, 10.0, 10.0, 1.0};
  29 static GLfloat Delta = 1.0;
  30 static GLint Mode = 0;
  31
  32 /*static GLfloat Blue[4] = {0.0, 0.0, 1.0, 1.0};*/
  33 /*static GLfloat Gray[4] = {0.5, 0.5, 0.5, 1.0};*/
  34 static GLfloat Black[4] = {0.0, 0.0, 0.0, 1.0};
  35 static GLfloat White[4] = {1.0, 1.0, 1.0, 1.0};
  36
  37
  38
  39 static void Idle( void )
  40 {
  41    LightPos[0] += Delta;
  42    if (LightPos[0]>15.0)
  43       Delta = -1.0;
  44    else if (LightPos[0]<-15.0)
  45       Delta = 1.0;
  46
  47    glutPostRedisplay();
  48 }
  49
  50
  51 static void Display( void )
  52 {
  53    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
  54
  55    glLightfv(GL_LIGHT0, GL_POSITION, LightPos);
  56
  57    glPushMatrix();
  58    glRotatef(90.0, 1.0, 0.0, 0.0);
  59
  60    if (Mode==0) {
  61       /* Typical method: diffuse + specular + texture */
  62       glEnable(GL_TEXTURE_2D);
  63       glLightfv(GL_LIGHT0, GL_DIFFUSE, White);  /* enable diffuse */
  64       glLightfv(GL_LIGHT0, GL_SPECULAR, White);  /* enable specular */
  65 #ifdef GL_VERSION_1_2
  66       glLightModeli(GL_LIGHT_MODEL_COLOR_CONTROL, GL_SINGLE_COLOR);
  67 #endif
  68       glCallList(Sphere);
  69    }
  70    else if (Mode==1) {
  71       /* just specular highlight */
  72       glDisable(GL_TEXTURE_2D);
  73       glLightfv(GL_LIGHT0, GL_DIFFUSE, Black);  /* disable diffuse */
  74       glLightfv(GL_LIGHT0, GL_SPECULAR, White);  /* enable specular */
  75 #ifdef GL_VERSION_1_2
  76       glLightModeli(GL_LIGHT_MODEL_COLOR_CONTROL, GL_SINGLE_COLOR);
  77 #endif
  78       glCallList(Sphere);
  79    }
  80    else if (Mode==2) {
  81       /* diffuse textured */
  82       glEnable(GL_TEXTURE_2D);
  83       glLightfv(GL_LIGHT0, GL_DIFFUSE, White);  /* enable diffuse */
  84       glLightfv(GL_LIGHT0, GL_SPECULAR, Black);  /* disable specular */
  85 #ifdef GL_VERSION_1_2
  86       glLightModeli(GL_LIGHT_MODEL_COLOR_CONTROL, GL_SINGLE_COLOR);
  87 #endif
  88       glCallList(Sphere);
  89    }
  90    else if (Mode==3) {
  91       /* 2-pass: diffuse textured then add specular highlight*/
  92       glEnable(GL_TEXTURE_2D);
  93       glLightfv(GL_LIGHT0, GL_DIFFUSE, White);  /* enable diffuse */
  94       glLightfv(GL_LIGHT0, GL_SPECULAR, Black);  /* disable specular */
  95 #ifdef GL_VERSION_1_2
  96       glLightModeli(GL_LIGHT_MODEL_COLOR_CONTROL, GL_SINGLE_COLOR);
  97 #endif
  98       glCallList(Sphere);
  99       /* specular highlight */
 100       glDepthFunc(GL_EQUAL);  /* redraw same pixels */
 101       glDisable(GL_TEXTURE_2D);
 102       glEnable(GL_BLEND);  /* add */
 103       glLightfv(GL_LIGHT0, GL_DIFFUSE, Black);  /* disable diffuse */
 104       glLightfv(GL_LIGHT0, GL_SPECULAR, White);  /* enable specular */
 105       glCallList(Sphere);
 106       glDepthFunc(GL_LESS);
 107       glDisable(GL_BLEND);
 108    }
 109    else if (Mode==4) {
 110       /* OpenGL 1.2's separate diffuse and specular color */
 111       glEnable(GL_TEXTURE_2D);
 112       glLightfv(GL_LIGHT0, GL_DIFFUSE, White);  /* enable diffuse */
 113       glLightfv(GL_LIGHT0, GL_SPECULAR, White);  /* enable specular */
 114 #ifdef GL_VERSION_1_2
 115       glLightModeli(GL_LIGHT_MODEL_COLOR_CONTROL, GL_SEPARATE_SPECULAR_COLOR);
 116 #endif
 117       glCallList(Sphere);
 118    }
 119
 120    glPopMatrix();
 121
 122    glutSwapBuffers();
 123 }
 124
 125
 126 static void Reshape( int width, int height )
 127 {
 128    glViewport( 0, 0, width, height );
 129    glMatrixMode( GL_PROJECTION );
 130    glLoadIdentity();
 131    glFrustum( -1.0, 1.0, -1.0, 1.0, 5.0, 25.0 );
 132    glMatrixMode( GL_MODELVIEW );
 133    glLoadIdentity();
 134    glTranslatef( 0.0, 0.0, -12.0 );
 135 }
 136
 137
 138 static void Key( unsigned char key, int x, int y )
 139 {
 140    (void) x;
 141    (void) y;
 142    switch (key) {
 143       case 27:
 144          exit(0);
 145          break;
 146    }
 147    glutPostRedisplay();
 148 }
 149
 150
 151 static void SpecialKey( int key, int x, int y )
 152 {
 153    (void) x;
 154    (void) y;
 155    switch (key) {
 156       case GLUT_KEY_UP:
 157          break;
 158       case GLUT_KEY_DOWN:
 159          break;
 160    }
 161    glutPostRedisplay();
 162 }
 163
 164
 165 static void Init( void )
 166 {
 167    int i, j;
 168    GLubyte texImage[64][64][3];
 169
 170    glEnable(GL_LIGHTING);
 171    glEnable(GL_LIGHT0);
 172    glLightModeli(GL_LIGHT_MODEL_TWO_SIDE, 0);
 173    glLightModelfv(GL_LIGHT_MODEL_AMBIENT, Black);
 174
 175    glMaterialfv(GL_FRONT, GL_DIFFUSE, White);
 176    glMaterialfv(GL_FRONT, GL_SPECULAR, White);
 177    glMaterialf(GL_FRONT, GL_SHININESS, 20.0);
 178
 179    /* Actually, these are set again later */
 180    glLightfv(GL_LIGHT0, GL_DIFFUSE, White);
 181    glLightfv(GL_LIGHT0, GL_SPECULAR, White);
 182
 183    Quadric = gluNewQuadric();
 184    gluQuadricTexture( Quadric, GL_TRUE );
 185
 186    Sphere= glGenLists(1);
 187    glNewList( Sphere, GL_COMPILE );
 188    gluSphere( Quadric, 1.0, 24, 24 );
 189    glEndList();
 190
 191    glEnable(GL_DEPTH_TEST);
 192    glEnable(GL_CULL_FACE);
 193
 194    for (i=0;i<64;i++) {
 195       for (j=0;j<64;j++) {
 196          int k = ((i>>3)&1) ^ ((j>>3)&1);
 197          texImage[i][j][0] = 255*k;
 198          texImage[i][j][1] = 255*(1-k);
 199          texImage[i][j][2] = 0;
 200       }
 201    }
 202
 203    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
 204    glTexImage2D( GL_TEXTURE_2D,
 205                  0,
 206                  3,
 207                  64, 64,
 208                  0,
 209                  GL_RGB, GL_UNSIGNED_BYTE,
 210                  texImage );
 211    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
 212    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
 213    glEnable(GL_TEXTURE_2D);
 214
 215    glBlendFunc(GL_ONE, GL_ONE);
 216 }
 217
 218
 219 static void ModeMenu(int entry)
 220 {
 221    if (entry==99)
 222       exit(0);
 223    Mode = entry;
 224 }
 225
 226
 227 int main( int argc, char *argv[] )
 228 {
 229
 230    glutInit( &argc, argv );
 231    glutInitWindowPosition( 0, 0 );
 232    glutInitWindowSize( 300, 300 );
 233
 234    glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH );
 235
 236    glutCreateWindow( "spectex" );
 237
 238    Init();
 239
 240    glutReshapeFunc( Reshape );
 241    glutKeyboardFunc( Key );
 242    glutSpecialFunc( SpecialKey );
 243    glutDisplayFunc( Display );
 244    glutIdleFunc( Idle );
 245
 246    glutCreateMenu( ModeMenu );
 247    glutAddMenuEntry("1-pass lighting + texturing", 0);
 248    glutAddMenuEntry("specular lighting", 1);
 249    glutAddMenuEntry("diffuse lighting + texturing", 2);
 250    glutAddMenuEntry("2-pass lighting + texturing", 3);
 251 #ifdef GL_VERSION_1_2
 252    glutAddMenuEntry("OpenGL 1.2 separate specular", 4);
 253 #endif
 254    glutAddMenuEntry("Quit", 99);
 255    glutAttachMenu(GLUT_RIGHT_BUTTON);
 256
 257    glutMainLoop();
 258    return 0;
 259 }