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/glew.h>
  13 #include <GL/glut.h>
  14 #include "shaderutil.h"
  15
  16
  17 static GLuint FragShader;
  18 static GLuint VertShader;
  19 static GLuint Program;
  20
  21 static GLint Win = 0;
  22 static GLint WinWidth = 500, WinHeight = 500;
  23 static GLboolean Anim = GL_TRUE;
  24 static GLboolean Bitmap = GL_FALSE;
  25 static GLfloat Xrot = 20.0f, Yrot = 70.0f;
  26 static GLint uTex, uScale;
  27 static GLuint Textures[2];
  28
  29 #define TEX_WIDTH 16
  30 #define TEX_HEIGHT 8
  31
  32
  33 static void
  34 BitmapText(const char *s)
  35 {
  36    while (*s) {
  37       glutBitmapCharacter(GLUT_BITMAP_8_BY_13, (int) *s);
  38       s++;
  39    }
  40 }
  41
  42
  43 static void
  44 Redisplay(void)
  45 {
  46    static const GLfloat px[3] = { 1.2, 0, 0};
  47    static const GLfloat nx[3] = {-1.2, 0, 0};
  48
  49    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  50
  51    glPushMatrix();
  52    glRotatef(Xrot, 1.0f, 0.0f, 0.0f);
  53    glRotatef(Yrot, 0.0f, 1.0f, 0.0f);
  54
  55    glEnable(GL_LIGHTING);
  56
  57    glPushMatrix();
  58    glScalef(0.5, 0.5, 0.5);
  59    glutSolidDodecahedron();
  60    glPopMatrix();
  61
  62    glDisable(GL_LIGHTING);
  63
  64    glColor3f(0, 1, 0);
  65    glBegin(GL_LINES);
  66    glVertex3f(-1, 0, 0);
  67    glVertex3f( 1, 0, 0);
  68    glEnd();
  69
  70    glColor3f(1, 1, 0);
  71
  72    if (Bitmap) {
  73       glRasterPos3fv(px);
  74       BitmapText("+X");
  75       glRasterPos3fv(nx);
  76       BitmapText("-X");
  77    }
  78    else {
  79       glUseProgram(Program);
  80
  81       /* vertex positions (deltas) depend on texture size and window size */
  82       if (uScale != -1) {
  83          glUniform2f(uScale,
  84                           2.0 * TEX_WIDTH / WinWidth,
  85                           2.0 * TEX_HEIGHT / WinHeight);
  86       }
  87
  88       /* draw +X */
  89       glBindTexture(GL_TEXTURE_2D, Textures[0]);
  90       glBegin(GL_QUADS);
  91       glTexCoord2f(0, 0);  glVertex3fv(px);
  92       glTexCoord2f(1, 0);  glVertex3fv(px);
  93       glTexCoord2f(1, 1);  glVertex3fv(px);
  94       glTexCoord2f(0, 1);  glVertex3fv(px);
  95       glEnd();
  96
  97       /* draw -X */
  98       glBindTexture(GL_TEXTURE_2D, Textures[1]);
  99       glBegin(GL_QUADS);
 100       glTexCoord2f(0, 0);  glVertex3fv(nx);
 101       glTexCoord2f(1, 0);  glVertex3fv(nx);
 102       glTexCoord2f(1, 1);  glVertex3fv(nx);
 103       glTexCoord2f(0, 1);  glVertex3fv(nx);
 104       glEnd();
 105
 106       glUseProgram(0);
 107    }
 108
 109    glPopMatrix();
 110
 111    glutSwapBuffers();
 112 }
 113
 114
 115 static void
 116 Idle(void)
 117 {
 118    Yrot = glutGet(GLUT_ELAPSED_TIME) * 0.01;
 119    glutPostRedisplay();
 120 }
 121
 122
 123 static void
 124 Reshape(int width, int height)
 125 {
 126    WinWidth = width;
 127    WinHeight = height;
 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(0.0f, 0.0f, -10.0f);
 135 }
 136
 137
 138 static void
 139 Key(unsigned char key, int x, int y)
 140 {
 141   (void) x;
 142   (void) y;
 143
 144    switch(key) {
 145    case ' ':
 146    case 'a':
 147       Anim = !Anim;
 148       if (Anim)
 149          glutIdleFunc(Idle);
 150       else
 151          glutIdleFunc(NULL);
 152       break;
 153    case 'b':
 154       Bitmap = !Bitmap;
 155       if (Bitmap)
 156          printf("Using glBitmap\n");
 157       else
 158          printf("Using billboard texture\n");
 159       break;
 160    case 27:
 161       glDeleteShader(FragShader);
 162       glDeleteShader(VertShader);
 163       glDeleteProgram(Program);
 164       glutDestroyWindow(Win);
 165       exit(0);
 166    }
 167    glutPostRedisplay();
 168 }
 169
 170
 171 static void
 172 SpecialKey(int key, int x, int y)
 173 {
 174    const GLfloat step = 0.125f;
 175    switch(key) {
 176    case GLUT_KEY_UP:
 177       Xrot -= step;
 178       break;
 179    case GLUT_KEY_DOWN:
 180       Xrot += step;
 181       break;
 182    case GLUT_KEY_LEFT:
 183       Yrot -= step;
 184       break;
 185    case GLUT_KEY_RIGHT:
 186       Yrot += step;
 187       break;
 188    }
 189    /*printf("Xrot: %f  Yrot: %f\n", Xrot, Yrot);*/
 190    glutPostRedisplay();
 191 }
 192
 193
 194 static void
 195 MakeTexImage(const char *p, GLuint texobj)
 196 {
 197    GLubyte image[TEX_HEIGHT][TEX_WIDTH];
 198    GLuint i, j, k;
 199
 200    for (i = 0; i < TEX_HEIGHT; i++) {
 201       for (j = 0; j < TEX_WIDTH; j++) {
 202          k = i * TEX_WIDTH + j;
 203          if (p[k] == ' ') {
 204             image[i][j] = 0;
 205          }
 206          else {
 207             image[i][j] = 255;
 208          }
 209       }
 210    }
 211
 212    glBindTexture(GL_TEXTURE_2D, texobj);
 213    glTexImage2D(GL_TEXTURE_2D, 0, GL_INTENSITY, TEX_WIDTH, TEX_HEIGHT, 0,
 214                 GL_RED, GL_UNSIGNED_BYTE, image);
 215    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 1);
 216    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
 217    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
 218 }
 219
 220
 221 static void
 222 MakeBitmapTextures(void)
 223 {
 224    const char *px =
 225       "        X     X "
 226       "   X     X   X  "
 227       "   X      X X   "
 228       " XXXXX     X    "
 229       "   X      X X   "
 230       "   X     X   X  "
 231       "        X     X "
 232       "        X     X ";
 233    const char *nx =
 234       "        X     X "
 235       "         X   X  "
 236       "          X X   "
 237       " XXXXX     X    "
 238       "          X X   "
 239       "         X   X  "
 240       "        X     X "
 241       "        X     X ";
 242    glGenTextures(2, Textures);
 243    MakeTexImage(px, Textures[0]);
 244    MakeTexImage(nx, Textures[1]);
 245 }
 246
 247
 248 static void
 249 Init(void)
 250 {
 251    /* Fragment shader: modulate raster color by texture, discard fragments
 252     * with alpha < 1.0
 253     */
 254    static const char *fragShaderText =
 255       "uniform sampler2D tex2d; \n"
 256       "void main() {\n"
 257       "   vec4 c = texture2D(tex2d, gl_TexCoord[0].xy); \n"
 258       "   if (c.w < 1.0) \n"
 259       "      discard; \n"
 260       "   gl_FragColor = c * gl_Color; \n"
 261       "}\n";
 262    /* Vertex shader: compute new vertex position based on incoming vertex pos,
 263     * texcoords and special scale factor.
 264     */
 265    static const char *vertShaderText =
 266       "uniform vec2 scale; \n"
 267       "void main() {\n"
 268       "   vec4 p = gl_ModelViewProjectionMatrix * gl_Vertex;\n"
 269       "   gl_Position.xy = p.xy + gl_MultiTexCoord0.xy * scale * p.w; \n"
 270       "   gl_Position.zw = p.zw; \n"
 271       "   gl_TexCoord[0] = gl_MultiTexCoord0; \n"
 272       "   gl_FrontColor = gl_Color; \n"
 273       "}\n";
 274
 275    if (!ShadersSupported())
 276       exit(1);
 277
 278    VertShader = CompileShaderText(GL_VERTEX_SHADER, vertShaderText);
 279    FragShader = CompileShaderText(GL_FRAGMENT_SHADER, fragShaderText);
 280    Program = LinkShaders(VertShader, FragShader);
 281
 282    glUseProgram(Program);
 283
 284    uScale = glGetUniformLocation(Program, "scale");
 285    uTex = glGetUniformLocation(Program, "tex2d");
 286    if (uTex != -1) {
 287       glUniform1i(uTex, 0);  /* tex unit 0 */
 288    }
 289
 290    glUseProgram(0);
 291
 292    glClearColor(0.3f, 0.3f, 0.3f, 0.0f);
 293    glEnable(GL_DEPTH_TEST);
 294    glEnable(GL_NORMALIZE);
 295    glEnable(GL_LIGHT0);
 296
 297    MakeBitmapTextures();
 298 }
 299
 300
 301 int
 302 main(int argc, char *argv[])
 303 {
 304    glutInit(&argc, argv);
 305    glutInitWindowSize(WinWidth, WinHeight);
 306    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
 307    Win = glutCreateWindow(argv[0]);
 308    glewInit();
 309    glutReshapeFunc(Reshape);
 310    glutKeyboardFunc(Key);
 311    glutSpecialFunc(SpecialKey);
 312    glutDisplayFunc(Redisplay);
 313    if (Anim)
 314       glutIdleFunc(Idle);
 315    Init();
 316    glutMainLoop();
 317    return 0;
 318 }
 319
 320