src/egl/opengles2/es2gears.c

   1 /*
   2  * Copyright (C) 1999-2001  Brian Paul   All Rights Reserved.
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice shall be included
  12  * in all copies or substantial portions of the Software.
  13  *
  14  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  15  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  17  * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  18  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  19  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  20  */
  21
  22 /*
  23  * Ported to GLES2.
  24  * Kristian Høgsberg <krh@bitplanet.net>
  25  * May 3, 2010
  26  *
  27  * Improve GLES2 port:
  28  *   * Refactor gear drawing.
  29  *   * Use correct normals for surfaces.
  30  *   * Improve shader.
  31  *   * Use perspective projection transformation.
  32  *   * Add FPS count.
  33  *   * Add comments.
  34  * Alexandros Frantzis <alexandros.frantzis@linaro.org>
  35  * Jul 13, 2010
  36  */
  37
  38 #define GL_GLEXT_PROTOTYPES
  39 #define EGL_EGLEXT_PROTOTYPES
  40
  41 #define _GNU_SOURCE
  42
  43 #include <math.h>
  44 #include <stdlib.h>
  45 #include <stdio.h>
  46 #include <string.h>
  47 #include <sys/time.h>
  48 #include <unistd.h>
  49 #include <GLES2/gl2.h>
  50 #include <EGL/egl.h>
  51 #include <EGL/eglext.h>
  52 #include "eglut.h"
  53
  54 #define STRIPS_PER_TOOTH 7
  55 #define VERTICES_PER_TOOTH 34
  56 #define GEAR_VERTEX_STRIDE 6
  57
  58 /**
  59  * Struct describing the vertices in triangle strip
  60  */
  61 struct vertex_strip {
  62    /** The first vertex in the strip */
  63    GLint first;
  64    /** The number of consecutive vertices in the strip after the first */
  65    GLint count;
  66 };
  67
  68 /* Each vertex consist of GEAR_VERTEX_STRIDE GLfloat attributes */
  69 typedef GLfloat GearVertex[GEAR_VERTEX_STRIDE];
  70
  71 /**
  72  * Struct representing a gear.
  73  */
  74 struct gear {
  75    /** The array of vertices comprising the gear */
  76    GearVertex *vertices;
  77    /** The number of vertices comprising the gear */
  78    int nvertices;
  79    /** The array of triangle strips comprising the gear */
  80    struct vertex_strip *strips;
  81    /** The number of triangle strips comprising the gear */
  82    int nstrips;
  83    /** The Vertex Buffer Object holding the vertices in the graphics card */
  84    GLuint vbo;
  85 };
  86
  87 /** The view rotation [x, y, z] */
  88 static GLfloat view_rot[3] = { 20.0, 30.0, 0.0 };
  89 /** The gears */
  90 static struct gear *gear1, *gear2, *gear3;
  91 /** The current gear rotation angle */
  92 static GLfloat angle = 0.0;
  93 /** The location of the shader uniforms */
  94 static GLuint ModelViewProjectionMatrix_location,
  95               NormalMatrix_location,
  96               LightSourcePosition_location,
  97               MaterialColor_location;
  98 /** The projection matrix */
  99 static GLfloat ProjectionMatrix[16];
 100 /** The direction of the directional light for the scene */
 101 static const GLfloat LightSourcePosition[4] = { 5.0, 5.0, 10.0, 1.0};
 102
 103 /**
 104  * Fills a gear vertex.
 105  *
 106  * @param v the vertex to fill
 107  * @param x the x coordinate
 108  * @param y the y coordinate
 109  * @param z the z coortinate
 110  * @param n pointer to the normal table
 111  *
 112  * @return the operation error code
 113  */
 114 static GearVertex *
 115 vert(GearVertex *v, GLfloat x, GLfloat y, GLfloat z, GLfloat n[3])
 116 {
 117    v[0][0] = x;
 118    v[0][1] = y;
 119    v[0][2] = z;
 120    v[0][3] = n[0];
 121    v[0][4] = n[1];
 122    v[0][5] = n[2];
 123
 124    return v + 1;
 125 }
 126
 127 /**
 128  *  Create a gear wheel.
 129  *
 130  *  @param inner_radius radius of hole at center
 131  *  @param outer_radius radius at center of teeth
 132  *  @param width width of gear
 133  *  @param teeth number of teeth
 134  *  @param tooth_depth depth of tooth
 135  *
 136  *  @return pointer to the constructed struct gear
 137  */
 138 static struct gear *
 139 create_gear(GLfloat inner_radius, GLfloat outer_radius, GLfloat width,
 140       GLint teeth, GLfloat tooth_depth)
 141 {
 142    GLfloat r0, r1, r2;
 143    GLfloat da;
 144    GearVertex *v;
 145    struct gear *gear;
 146    double s[5], c[5];
 147    GLfloat normal[3];
 148    int cur_strip = 0;
 149    int i;
 150
 151    /* Allocate memory for the gear */
 152    gear = malloc(sizeof *gear);
 153    if (gear == NULL)
 154       return NULL;
 155
 156    /* Calculate the radii used in the gear */
 157    r0 = inner_radius;
 158    r1 = outer_radius - tooth_depth / 2.0;
 159    r2 = outer_radius + tooth_depth / 2.0;
 160
 161    da = 2.0 * M_PI / teeth / 4.0;
 162
 163    /* Allocate memory for the triangle strip information */
 164    gear->nstrips = STRIPS_PER_TOOTH * teeth;
 165    gear->strips = calloc(gear->nstrips, sizeof (*gear->strips));
 166
 167    /* Allocate memory for the vertices */
 168    gear->vertices = calloc(VERTICES_PER_TOOTH * teeth, sizeof(*gear->vertices));
 169    v = gear->vertices;
 170
 171    for (i = 0; i < teeth; i++) {
 172       /* Calculate needed sin/cos for varius angles */
 173       sincos(i * 2.0 * M_PI / teeth, &s[0], &c[0]);
 174       sincos(i * 2.0 * M_PI / teeth + da, &s[1], &c[1]);
 175       sincos(i * 2.0 * M_PI / teeth + da * 2, &s[2], &c[2]);
 176       sincos(i * 2.0 * M_PI / teeth + da * 3, &s[3], &c[3]);
 177       sincos(i * 2.0 * M_PI / teeth + da * 4, &s[4], &c[4]);
 178
 179       /* A set of macros for making the creation of the gears easier */
 180 #define  GEAR_POINT(r, da) { (r) * c[(da)], (r) * s[(da)] }
 181 #define  SET_NORMAL(x, y, z) do { \
 182    normal[0] = (x); normal[1] = (y); normal[2] = (z); \
 183 } while(0)
 184
 185 #define  GEAR_VERT(v, point, sign) vert((v), p[(point)].x, p[(point)].y, (sign) * width * 0.5, normal)
 186
 187 #define START_STRIP do { \
 188    gear->strips[cur_strip].first = v - gear->vertices; \
 189 } while(0);
 190
 191 #define END_STRIP do { \
 192    int _tmp = (v - gear->vertices); \
 193    gear->strips[cur_strip].count = _tmp - gear->strips[cur_strip].first; \
 194    cur_strip++; \
 195 } while (0)
 196
 197 #define QUAD_WITH_NORMAL(p1, p2) do { \
 198    SET_NORMAL((p[(p1)].y - p[(p2)].y), -(p[(p1)].x - p[(p2)].x), 0); \
 199    v = GEAR_VERT(v, (p1), -1); \
 200    v = GEAR_VERT(v, (p1), 1); \
 201    v = GEAR_VERT(v, (p2), -1); \
 202    v = GEAR_VERT(v, (p2), 1); \
 203 } while(0)
 204
 205       struct point {
 206          GLfloat x;
 207          GLfloat y;
 208       };
 209
 210       /* Create the 7 points (only x,y coords) used to draw a tooth */
 211       struct point p[7] = {
 212          GEAR_POINT(r2, 1), // 0
 213          GEAR_POINT(r2, 2), // 1
 214          GEAR_POINT(r1, 0), // 2
 215          GEAR_POINT(r1, 3), // 3
 216          GEAR_POINT(r0, 0), // 4
 217          GEAR_POINT(r1, 4), // 5
 218          GEAR_POINT(r0, 4), // 6
 219       };
 220
 221       /* Front face */
 222       START_STRIP;
 223       SET_NORMAL(0, 0, 1.0);
 224       v = GEAR_VERT(v, 0, +1);
 225       v = GEAR_VERT(v, 1, +1);
 226       v = GEAR_VERT(v, 2, +1);
 227       v = GEAR_VERT(v, 3, +1);
 228       v = GEAR_VERT(v, 4, +1);
 229       v = GEAR_VERT(v, 5, +1);
 230       v = GEAR_VERT(v, 6, +1);
 231       END_STRIP;
 232
 233       /* Inner face */
 234       START_STRIP;
 235       QUAD_WITH_NORMAL(4, 6);
 236       END_STRIP;
 237
 238       /* Back face */
 239       START_STRIP;
 240       SET_NORMAL(0, 0, -1.0);
 241       v = GEAR_VERT(v, 6, -1);
 242       v = GEAR_VERT(v, 5, -1);
 243       v = GEAR_VERT(v, 4, -1);
 244       v = GEAR_VERT(v, 3, -1);
 245       v = GEAR_VERT(v, 2, -1);
 246       v = GEAR_VERT(v, 1, -1);
 247       v = GEAR_VERT(v, 0, -1);
 248       END_STRIP;
 249
 250       /* Outer face */
 251       START_STRIP;
 252       QUAD_WITH_NORMAL(0, 2);
 253       END_STRIP;
 254
 255       START_STRIP;
 256       QUAD_WITH_NORMAL(1, 0);
 257       END_STRIP;
 258
 259       START_STRIP;
 260       QUAD_WITH_NORMAL(3, 1);
 261       END_STRIP;
 262
 263       START_STRIP;
 264       QUAD_WITH_NORMAL(5, 3);
 265       END_STRIP;
 266    }
 267
 268    gear->nvertices = (v - gear->vertices);
 269
 270    /* Store the vertices in a vertex buffer object (VBO) */
 271    glGenBuffers(1, &gear->vbo);
 272    glBindBuffer(GL_ARRAY_BUFFER, gear->vbo);
 273    glBufferData(GL_ARRAY_BUFFER, gear->nvertices * sizeof(GearVertex),
 274          gear->vertices, GL_STATIC_DRAW);
 275
 276    return gear;
 277 }
 278
 279 /**
 280  * Multiplies two 4x4 matrices.
 281  *
 282  * The result is stored in matrix m.
 283  *
 284  * @param m the first matrix to multiply
 285  * @param n the second matrix to multiply
 286  */
 287 static void
 288 multiply(GLfloat *m, const GLfloat *n)
 289 {
 290    GLfloat tmp[16];
 291    const GLfloat *row, *column;
 292    div_t d;
 293    int i, j;
 294
 295    for (i = 0; i < 16; i++) {
 296       tmp[i] = 0;
 297       d = div(i, 4);
 298       row = n + d.quot * 4;
 299       column = m + d.rem;
 300       for (j = 0; j < 4; j++)
 301          tmp[i] += row[j] * column[j * 4];
 302    }
 303    memcpy(m, &tmp, sizeof tmp);
 304 }
 305
 306 /**
 307  * Rotates a 4x4 matrix.
 308  *
 309  * @param[in,out] m the matrix to rotate
 310  * @param angle the angle to rotate
 311  * @param x the x component of the direction to rotate to
 312  * @param y the y component of the direction to rotate to
 313  * @param z the z component of the direction to rotate to
 314  */
 315 static void
 316 rotate(GLfloat *m, GLfloat angle, GLfloat x, GLfloat y, GLfloat z)
 317 {
 318    double s, c;
 319
 320    sincos(angle, &s, &c);
 321    GLfloat r[16] = {
 322       x * x * (1 - c) + c,     y * x * (1 - c) + z * s, x * z * (1 - c) - y * s, 0,
 323       x * y * (1 - c) - z * s, y * y * (1 - c) + c,     y * z * (1 - c) + x * s, 0,
 324       x * z * (1 - c) + y * s, y * z * (1 - c) - x * s, z * z * (1 - c) + c,     0,
 325       0, 0, 0, 1
 326    };
 327
 328    multiply(m, r);
 329 }
 330
 331
 332 /**
 333  * Translates a 4x4 matrix.
 334  *
 335  * @param[in,out] m the matrix to translate
 336  * @param x the x component of the direction to translate to
 337  * @param y the y component of the direction to translate to
 338  * @param z the z component of the direction to translate to
 339  */
 340 static void
 341 translate(GLfloat *m, GLfloat x, GLfloat y, GLfloat z)
 342 {
 343    GLfloat t[16] = { 1, 0, 0, 0,  0, 1, 0, 0,  0, 0, 1, 0,  x, y, z, 1 };
 344
 345    multiply(m, t);
 346 }
 347
 348 /**
 349  * Creates an identity 4x4 matrix.
 350  *
 351  * @param m the matrix make an identity matrix
 352  */
 353 static void
 354 identity(GLfloat *m)
 355 {
 356    GLfloat t[16] = {
 357       1.0, 0.0, 0.0, 0.0,
 358       0.0, 1.0, 0.0, 0.0,
 359       0.0, 0.0, 1.0, 0.0,
 360       0.0, 0.0, 0.0, 1.0,
 361    };
 362
 363    memcpy(m, t, sizeof(t));
 364 }
 365
 366 /**
 367  * Transposes a 4x4 matrix.
 368  *
 369  * @param m the matrix to transpose
 370  */
 371 static void
 372 transpose(GLfloat *m)
 373 {
 374    GLfloat t[16] = {
 375       m[0], m[4], m[8],  m[12],
 376       m[1], m[5], m[9],  m[13],
 377       m[2], m[6], m[10], m[14],
 378       m[3], m[7], m[11], m[15]};
 379
 380    memcpy(m, t, sizeof(t));
 381 }
 382
 383 /**
 384  * Inverts a 4x4 matrix.
 385  *
 386  * This function can currently handle only pure translation-rotation matrices.
 387  * Read http://www.gamedev.net/community/forums/topic.asp?topic_id=425118
 388  * for an explanation.
 389  */
 390 static void
 391 invert(GLfloat *m)
 392 {
 393    GLfloat t[16];
 394    identity(t);
 395
 396    // Extract and invert the translation part 't'. The inverse of a
 397    // translation matrix can be calculated by negating the translation
 398    // coordinates.
 399    t[12] = -m[12]; t[13] = -m[13]; t[14] = -m[14];
 400
 401    // Invert the rotation part 'r'. The inverse of a rotation matrix is
 402    // equal to its transpose.
 403    m[12] = m[13] = m[14] = 0;
 404    transpose(m);
 405
 406    // inv(m) = inv(r) * inv(t)
 407    multiply(m, t);
 408 }
 409
 410 /**
 411  * Calculate a frustum projection transformation.
 412  *
 413  * @param m the matrix to save the transformation in
 414  * @param l the left plane distance
 415  * @param r the right plane distance
 416  * @param b the bottom plane distance
 417  * @param t the top plane distance
 418  * @param n the near plane distance
 419  * @param f the far plane distance
 420  */
 421 static void
 422 frustum(GLfloat *m, GLfloat l, GLfloat r, GLfloat b, GLfloat t, GLfloat n, GLfloat f)
 423 {
 424    GLfloat tmp[16];
 425    identity(tmp);
 426
 427    GLfloat deltaX = r - l;
 428    GLfloat deltaY = t - b;
 429    GLfloat deltaZ = f - n;
 430
 431    tmp[0] = (2 * n) / deltaX;
 432    tmp[5] = (2 * n) / deltaY;
 433    tmp[8] = (r + l) / deltaX;
 434    tmp[9] = (t + b) / deltaY;
 435    tmp[10] = -(f + n) / deltaZ;
 436    tmp[11] = -1;
 437    tmp[14] = -(2 * f * n) / deltaZ;
 438    tmp[15] = 0;
 439
 440    memcpy(m, tmp, sizeof(tmp));
 441 }
 442
 443 /**
 444  * Draws a gear.
 445  *
 446  * @param gear the gear to draw
 447  * @param transform the current transformation matrix
 448  * @param x the x position to draw the gear at
 449  * @param y the y position to draw the gear at
 450  * @param angle the rotation angle of the gear
 451  * @param color the color of the gear
 452  */
 453 static void
 454 draw_gear(struct gear *gear, GLfloat *transform,
 455       GLfloat x, GLfloat y, GLfloat angle, const GLfloat color[4])
 456 {
 457    GLfloat model_view[16];
 458    GLfloat normal_matrix[16];
 459    GLfloat model_view_projection[16];
 460
 461    /* Translate and rotate the gear */
 462    memcpy(model_view, transform, sizeof (model_view));
 463    translate(model_view, x, y, 0);
 464    rotate(model_view, 2 * M_PI * angle / 360.0, 0, 0, 1);
 465
 466    /* Create and set the ModelViewProjectionMatrix */
 467    memcpy(model_view_projection, ProjectionMatrix, sizeof(model_view_projection));
 468    multiply(model_view_projection, model_view);
 469
 470    glUniformMatrix4fv(ModelViewProjectionMatrix_location, 1, GL_FALSE,
 471                       model_view_projection);
 472
 473    /*
 474     * Create and set the NormalMatrix. It's the inverse transpose of the
 475     * ModelView matrix.
 476     */
 477    memcpy(normal_matrix, model_view, sizeof (normal_matrix));
 478    invert(normal_matrix);
 479    transpose(normal_matrix);
 480    glUniformMatrix4fv(NormalMatrix_location, 1, GL_FALSE, normal_matrix);
 481
 482    /* Set the gear color */
 483    glUniform4fv(MaterialColor_location, 1, color);
 484
 485    /* Set the vertex buffer object to use */
 486    glBindBuffer(GL_ARRAY_BUFFER, gear->vbo);
 487
 488    /* Set up the position of the attributes in the vertex buffer object */
 489    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE,
 490          6 * sizeof(GLfloat), NULL);
 491    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE,
 492          6 * sizeof(GLfloat), (GLfloat *) 0 + 3);
 493
 494    /* Enable the attributes */
 495    glEnableVertexAttribArray(0);
 496    glEnableVertexAttribArray(1);
 497
 498    /* Draw the triangle strips that comprise the gear */
 499    int n;
 500    for (n = 0; n < gear->nstrips; n++)
 501       glDrawArrays(GL_TRIANGLE_STRIP, gear->strips[n].first, gear->strips[n].count);
 502
 503    /* Disable the attributes */
 504    glDisableVertexAttribArray(1);
 505    glDisableVertexAttribArray(0);
 506 }
 507
 508 /**
 509  * Draws the gears.
 510  */
 511 static void
 512 gears_draw(void)
 513 {
 514    const static GLfloat red[4] = { 0.8, 0.1, 0.0, 1.0 };
 515    const static GLfloat green[4] = { 0.0, 0.8, 0.2, 1.0 };
 516    const static GLfloat blue[4] = { 0.2, 0.2, 1.0, 1.0 };
 517    GLfloat transform[16];
 518    identity(transform);
 519
 520    glClearColor(0.0, 0.0, 0.0, 0.0);
 521    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 522
 523    /* Translate and rotate the view */
 524    translate(transform, 0, 0, -40);
 525    rotate(transform, 2 * M_PI * view_rot[0] / 360.0, 1, 0, 0);
 526    rotate(transform, 2 * M_PI * view_rot[1] / 360.0, 0, 1, 0);
 527    rotate(transform, 2 * M_PI * view_rot[2] / 360.0, 0, 0, 1);
 528
 529    /* Draw the gears */
 530    draw_gear(gear1, transform, -3.0, -2.0, angle, red);
 531    draw_gear(gear2, transform, 3.1, -2.0, -2 * angle - 9.0, green);
 532    draw_gear(gear3, transform, -3.1, 4.2, -2 * angle - 25.0, blue);
 533 }
 534
 535 /**
 536  * Handles a new window size or exposure.
 537  *
 538  * @param width the window width
 539  * @param height the window height
 540  */
 541 static void
 542 gears_reshape(int width, int height)
 543 {
 544    /* Update the projection matrix */
 545    GLfloat h = (GLfloat)height / (GLfloat)width;
 546    frustum(ProjectionMatrix, -1.0, 1.0, -h, h, 5.0, 60.0);
 547
 548    /* Set the viewport */
 549    glViewport(0, 0, (GLint) width, (GLint) height);
 550 }
 551
 552 /**
 553  * Handles special eglut events.
 554  *
 555  * @param special the event to handle.
 556  */
 557 static void
 558 gears_special(int special)
 559 {
 560    switch (special) {
 561       case EGLUT_KEY_LEFT:
 562          view_rot[1] += 5.0;
 563          break;
 564       case EGLUT_KEY_RIGHT:
 565          view_rot[1] -= 5.0;
 566          break;
 567       case EGLUT_KEY_UP:
 568          view_rot[0] += 5.0;
 569          break;
 570       case EGLUT_KEY_DOWN:
 571          view_rot[0] -= 5.0;
 572          break;
 573    }
 574 }
 575
 576 static void
 577 gears_idle(void)
 578 {
 579    static int frames = 0;
 580    static double tRot0 = -1.0, tRate0 = -1.0;
 581    double dt, t = eglutGet(EGLUT_ELAPSED_TIME) / 1000.0;
 582
 583    if (tRot0 < 0.0)
 584       tRot0 = t;
 585    dt = t - tRot0;
 586    tRot0 = t;
 587
 588    /* advance rotation for next frame */
 589    angle += 70.0 * dt;  /* 70 degrees per second */
 590    if (angle > 3600.0)
 591       angle -= 3600.0;
 592
 593    eglutPostRedisplay();
 594    frames++;
 595
 596    if (tRate0 < 0.0)
 597       tRate0 = t;
 598    if (t - tRate0 >= 5.0) {
 599       GLfloat seconds = t - tRate0;
 600       GLfloat fps = frames / seconds;
 601       printf("%d frames in %3.1f seconds = %6.3f FPS\n", frames, seconds,
 602             fps);
 603       tRate0 = t;
 604       frames = 0;
 605    }
 606 }
 607
 608 static const char vertex_shader[] =
 609 "attribute vec3 position;\n"
 610 "attribute vec3 normal;\n"
 611 "\n"
 612 "uniform mat4 ModelViewProjectionMatrix;\n"
 613 "uniform mat4 NormalMatrix;\n"
 614 "uniform vec4 LightSourcePosition;\n"
 615 "uniform vec4 MaterialColor;\n"
 616 "\n"
 617 "varying vec4 Color;\n"
 618 "\n"
 619 "void main(void)\n"
 620 "{\n"
 621 "    // Transform the normal to eye coordinates\n"
 622 "    vec3 N = normalize(vec3(NormalMatrix * vec4(normal, 1.0)));\n"
 623 "\n"
 624 "    // The LightSourcePosition is actually its direction for directional light\n"
 625 "    vec3 L = normalize(LightSourcePosition.xyz);\n"
 626 "\n"
 627 "    float diffuse = max(dot(N, L), 0.0);\n"
 628 "    float ambient = 0.2;\n"
 629 "\n"
 630 "    // Multiply the diffuse value by the vertex color (which is fixed in this case)\n"
 631 "    // to get the actual color that we will use to draw this vertex with\n"
 632 "    Color = (ambient + diffuse) * MaterialColor;\n"
 633 "\n"
 634 "    // Transform the position to clip coordinates\n"
 635 "    gl_Position = ModelViewProjectionMatrix * vec4(position, 1.0);\n"
 636 "}";
 637
 638 static const char fragment_shader[] =
 639 "precision mediump float;\n"
 640 "varying vec4 Color;\n"
 641 "\n"
 642 "void main(void)\n"
 643 "{\n"
 644 "    gl_FragColor = Color;\n"
 645 "}";
 646
 647 static void
 648 gears_init(void)
 649 {
 650    GLuint v, f, program;
 651    const char *p;
 652    char msg[512];
 653
 654    glEnable(GL_CULL_FACE);
 655    glEnable(GL_DEPTH_TEST);
 656
 657    /* Compile the vertex shader */
 658    p = vertex_shader;
 659    v = glCreateShader(GL_VERTEX_SHADER);
 660    glShaderSource(v, 1, &p, NULL);
 661    glCompileShader(v);
 662    glGetShaderInfoLog(v, sizeof msg, NULL, msg);
 663    printf("vertex shader info: %s\n", msg);
 664
 665    /* Compile the fragment shader */
 666    p = fragment_shader;
 667    f = glCreateShader(GL_FRAGMENT_SHADER);
 668    glShaderSource(f, 1, &p, NULL);
 669    glCompileShader(f);
 670    glGetShaderInfoLog(f, sizeof msg, NULL, msg);
 671    printf("fragment shader info: %s\n", msg);
 672
 673    /* Create and link the shader program */
 674    program = glCreateProgram();
 675    glAttachShader(program, v);
 676    glAttachShader(program, f);
 677    glBindAttribLocation(program, 0, "position");
 678    glBindAttribLocation(program, 1, "normal");
 679
 680    glLinkProgram(program);
 681    glGetProgramInfoLog(program, sizeof msg, NULL, msg);
 682    printf("info: %s\n", msg);
 683
 684    /* Enable the shaders */
 685    glUseProgram(program);
 686
 687    /* Get the locations of the uniforms so we can access them */
 688    ModelViewProjectionMatrix_location = glGetUniformLocation(program, "ModelViewProjectionMatrix");
 689    NormalMatrix_location = glGetUniformLocation(program, "NormalMatrix");
 690    LightSourcePosition_location = glGetUniformLocation(program, "LightSourcePosition");
 691    MaterialColor_location = glGetUniformLocation(program, "MaterialColor");
 692
 693    /* Set the LightSourcePosition uniform which is constant throught the program */
 694    glUniform4fv(LightSourcePosition_location, 1, LightSourcePosition);
 695
 696    /* make the gears */
 697    gear1 = create_gear(1.0, 4.0, 1.0, 20, 0.7);
 698    gear2 = create_gear(0.5, 2.0, 2.0, 10, 0.7);
 699    gear3 = create_gear(1.3, 2.0, 0.5, 10, 0.7);
 700 }
 701
 702 int
 703 main(int argc, char *argv[])
 704 {
 705    /* Initialize the window */
 706    eglutInitWindowSize(300, 300);
 707    eglutInitAPIMask(EGLUT_OPENGL_ES2_BIT);
 708    eglutInit(argc, argv);
 709
 710    eglutCreateWindow("es2gears");
 711
 712    /* Set up eglut callback functions */
 713    eglutIdleFunc(gears_idle);
 714    eglutReshapeFunc(gears_reshape);
 715    eglutDisplayFunc(gears_draw);
 716    eglutSpecialFunc(gears_special);
 717
 718    /* Initialize the gears */
 719    gears_init();
 720
 721    eglutMainLoop();
 722
 723    return 0;
 724 }