progs/glsl/bitmap.c

   1 /**
   2  * Implement glRasterPos + glBitmap with textures + shaders.
   3  * Brian Paul
   4  * 14 May 2007
   5  */
   6
   7 #include <assert.h>
   8 #include <string.h>
   9 #include <stdio.h>
  10 #include <stdlib.h>
  11 #include <math.h>
  12 #include <GL/gl.h>
  13 #include <GL/glut.h>
  14 #include <GL/glext.h>
  15 #include "extfuncs.h"
  16 #include "shaderutil.h"
  17
  18
  19 static GLuint FragShader;
  20 static GLuint VertShader;
  21 static GLuint Program;
  22
  23 static GLint Win = 0;
  24 static GLint WinWidth = 500, WinHeight = 500;
  25 static GLboolean Anim = GL_TRUE;
  26 static GLboolean Bitmap = GL_FALSE;
  27 static GLfloat Xrot = 20.0f, Yrot = 70.0f;
  28 static GLint uTex, uScale;
  29 static GLuint Textures[2];
  30
  31 #define TEX_WIDTH 16
  32 #define TEX_HEIGHT 8
  33
  34
  35 static void
  36 BitmapText(const char *s)
  37 {
  38    while (*s) {
  39       glutBitmapCharacter(GLUT_BITMAP_8_BY_13, (int) *s);
  40       s++;
  41    }
  42 }
  43
  44
  45 static void
  46 Redisplay(void)
  47 {
  48    static const GLfloat px[3] = { 1.2, 0, 0};
  49    static const GLfloat nx[3] = {-1.2, 0, 0};
  50
  51    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  52
  53    glPushMatrix();
  54    glRotatef(Xrot, 1.0f, 0.0f, 0.0f);
  55    glRotatef(Yrot, 0.0f, 1.0f, 0.0f);
  56
  57    glEnable(GL_LIGHTING);
  58
  59    glPushMatrix();
  60    glScalef(0.5, 0.5, 0.5);
  61    glutSolidDodecahedron();
  62    glPopMatrix();
  63
  64    glDisable(GL_LIGHTING);
  65
  66    glColor3f(0, 1, 0);
  67    glBegin(GL_LINES);
  68    glVertex3f(-1, 0, 0);
  69    glVertex3f( 1, 0, 0);
  70    glEnd();
  71
  72    glColor3f(1, 1, 0);
  73
  74    if (Bitmap) {
  75       glRasterPos3fv(px);
  76       BitmapText("+X");
  77       glRasterPos3fv(nx);
  78       BitmapText("-X");
  79    }
  80    else {
  81       glUseProgram_func(Program);
  82
  83       /* vertex positions (deltas) depend on texture size and window size */
  84       if (uScale != -1) {
  85          glUniform2f_func(uScale,
  86                           2.0 * TEX_WIDTH / WinWidth,
  87                           2.0 * TEX_HEIGHT / WinHeight);
  88       }
  89
  90       /* draw +X */
  91       glBindTexture(GL_TEXTURE_2D, Textures[0]);
  92       glBegin(GL_QUADS);
  93       glTexCoord2f(0, 0);  glVertex3fv(px);
  94       glTexCoord2f(1, 0);  glVertex3fv(px);
  95       glTexCoord2f(1, 1);  glVertex3fv(px);
  96       glTexCoord2f(0, 1);  glVertex3fv(px);
  97       glEnd();
  98
  99       /* draw -X */
 100       glBindTexture(GL_TEXTURE_2D, Textures[1]);
 101       glBegin(GL_QUADS);
 102       glTexCoord2f(0, 0);  glVertex3fv(nx);
 103       glTexCoord2f(1, 0);  glVertex3fv(nx);
 104       glTexCoord2f(1, 1);  glVertex3fv(nx);
 105       glTexCoord2f(0, 1);  glVertex3fv(nx);
 106       glEnd();
 107
 108       glUseProgram_func(0);
 109    }
 110
 111    glPopMatrix();
 112
 113    glutSwapBuffers();
 114 }
 115
 116
 117 static void
 118 Idle(void)
 119 {
 120    Yrot = glutGet(GLUT_ELAPSED_TIME) * 0.01;
 121    glutPostRedisplay();
 122 }
 123
 124
 125 static void
 126 Reshape(int width, int height)
 127 {
 128    WinWidth = width;
 129    WinHeight = height;
 130    glViewport(0, 0, width, height);
 131    glMatrixMode(GL_PROJECTION);
 132    glLoadIdentity();
 133    glFrustum(-1.0, 1.0, -1.0, 1.0, 5.0, 25.0);
 134    glMatrixMode(GL_MODELVIEW);
 135    glLoadIdentity();
 136    glTranslatef(0.0f, 0.0f, -10.0f);
 137 }
 138
 139
 140 static void
 141 Key(unsigned char key, int x, int y)
 142 {
 143   (void) x;
 144   (void) y;
 145
 146    switch(key) {
 147    case ' ':
 148    case 'a':
 149       Anim = !Anim;
 150       if (Anim)
 151          glutIdleFunc(Idle);
 152       else
 153          glutIdleFunc(NULL);
 154       break;
 155    case 'b':
 156       Bitmap = !Bitmap;
 157       if (Bitmap)
 158          printf("Using glBitmap\n");
 159       else
 160          printf("Using billboard texture\n");
 161       break;
 162    case 27:
 163       glDeleteShader_func(FragShader);
 164       glDeleteShader_func(VertShader);
 165       glDeleteProgram_func(Program);
 166       glutDestroyWindow(Win);
 167       exit(0);
 168    }
 169    glutPostRedisplay();
 170 }
 171
 172
 173 static void
 174 SpecialKey(int key, int x, int y)
 175 {
 176    const GLfloat step = 0.125f;
 177    switch(key) {
 178    case GLUT_KEY_UP:
 179       Xrot -= step;
 180       break;
 181    case GLUT_KEY_DOWN:
 182       Xrot += step;
 183       break;
 184    case GLUT_KEY_LEFT:
 185       Yrot -= step;
 186       break;
 187    case GLUT_KEY_RIGHT:
 188       Yrot += step;
 189       break;
 190    }
 191    /*printf("Xrot: %f  Yrot: %f\n", Xrot, Yrot);*/
 192    glutPostRedisplay();
 193 }
 194
 195
 196 static void
 197 MakeTexImage(const char *p, GLuint texobj)
 198 {
 199    GLubyte image[TEX_HEIGHT][TEX_WIDTH];
 200    GLuint i, j, k;
 201
 202    for (i = 0; i < TEX_HEIGHT; i++) {
 203       for (j = 0; j < TEX_WIDTH; j++) {
 204          k = i * TEX_WIDTH + j;
 205          if (p[k] == ' ') {
 206             image[i][j] = 0;
 207          }
 208          else {
 209             image[i][j] = 255;
 210          }
 211       }
 212    }
 213
 214    glBindTexture(GL_TEXTURE_2D, texobj);
 215    glTexImage2D(GL_TEXTURE_2D, 0, GL_INTENSITY, TEX_WIDTH, TEX_HEIGHT, 0,
 216                 GL_RED, GL_UNSIGNED_BYTE, image);
 217    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 1);
 218    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
 219    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
 220 }
 221
 222
 223 static void
 224 MakeBitmapTextures(void)
 225 {
 226    const char *px =
 227       "        X     X "
 228       "   X     X   X  "
 229       "   X      X X   "
 230       " XXXXX     X    "
 231       "   X      X X   "
 232       "   X     X   X  "
 233       "        X     X "
 234       "        X     X ";
 235    const char *nx =
 236       "        X     X "
 237       "         X   X  "
 238       "          X X   "
 239       " XXXXX     X    "
 240       "          X X   "
 241       "         X   X  "
 242       "        X     X "
 243       "        X     X ";
 244    glGenTextures(2, Textures);
 245    MakeTexImage(px, Textures[0]);
 246    MakeTexImage(nx, Textures[1]);
 247 }
 248
 249
 250 static void
 251 Init(void)
 252 {
 253    /* Fragment shader: modulate raster color by texture, discard fragments
 254     * with alpha < 1.0
 255     */
 256    static const char *fragShaderText =
 257       "uniform sampler2D tex2d; \n"
 258       "void main() {\n"
 259       "   vec4 c = texture2D(tex2d, gl_TexCoord[0].xy); \n"
 260       "   if (c.w < 1.0) \n"
 261       "      discard; \n"
 262       "   gl_FragColor = c * gl_Color; \n"
 263       "}\n";
 264    /* Vertex shader: compute new vertex position based on incoming vertex pos,
 265     * texcoords and special scale factor.
 266     */
 267    static const char *vertShaderText =
 268       "uniform vec2 scale; \n"
 269       "void main() {\n"
 270       "   vec4 p = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
 271       "   gl_Position.xy = p.xy + gl_MultiTexCoord0.xy * scale * p.w; \n"
 272       "   gl_Position.zw = p.zw; \n"
 273       "   gl_TexCoord[0] = gl_MultiTexCoord0; \n"
 274       "   gl_FrontColor = gl_Color; \n"
 275       "}\n";
 276
 277    if (!ShadersSupported())
 278       exit(1);
 279
 280    GetExtensionFuncs();
 281
 282    VertShader = CompileShaderText(GL_VERTEX_SHADER, vertShaderText);
 283    FragShader = CompileShaderText(GL_FRAGMENT_SHADER, fragShaderText);
 284    Program = LinkShaders(VertShader, FragShader);
 285
 286    glUseProgram_func(Program);
 287
 288    uScale = glGetUniformLocation_func(Program, "scale");
 289    uTex = glGetUniformLocation_func(Program, "tex2d");
 290    if (uTex != -1) {
 291       glUniform1i_func(uTex, 0);  /* tex unit 0 */
 292    }
 293
 294    glUseProgram_func(0);
 295
 296    glClearColor(0.3f, 0.3f, 0.3f, 0.0f);
 297    glEnable(GL_DEPTH_TEST);
 298    glEnable(GL_NORMALIZE);
 299    glEnable(GL_LIGHT0);
 300
 301    MakeBitmapTextures();
 302 }
 303
 304
 305 int
 306 main(int argc, char *argv[])
 307 {
 308    glutInit(&argc, argv);
 309    glutInitWindowSize(WinWidth, WinHeight);
 310    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
 311    Win = glutCreateWindow(argv[0]);
 312    glutReshapeFunc(Reshape);
 313    glutKeyboardFunc(Key);
 314    glutSpecialFunc(SpecialKey);
 315    glutDisplayFunc(Redisplay);
 316    if (Anim)
 317       glutIdleFunc(Idle);
 318    Init();
 319    glutMainLoop();
 320    return 0;
 321 }
 322
 323