third_party/gles2_book/Chapter_13/ParticleSystem/ParticleSystem.c

   1 //
   2 // Book:      OpenGL(R) ES 2.0 Programming Guide
   3 // Authors:   Aaftab Munshi, Dan Ginsburg, Dave Shreiner
   4 // ISBN-10:   0321502795
   5 // ISBN-13:   9780321502797
   6 // Publisher: Addison-Wesley Professional
   7 // URLs:      http://safari.informit.com/9780321563835
   8 //            http://www.opengles-book.com
   9 //
  10
  11 // ParticleSystem.c
  12 //
  13 //    This is an example that demonstrates rendering a particle system
  14 //    using a vertex shader and point sprites.
  15 //
  16 #include <stdlib.h>
  17 #include <math.h>
  18 #include "esUtil.h"
  19
  20 #define NUM_PARTICLES   1000
  21 #define PARTICLE_SIZE   7
  22
  23 typedef struct
  24 {
  25    // Handle to a program object
  26    GLuint programObject;
  27
  28    // Attribute locations
  29    GLint  lifetimeLoc;
  30    GLint  startPositionLoc;
  31    GLint  endPositionLoc;
  32
  33    // Uniform location
  34    GLint timeLoc;
  35    GLint colorLoc;
  36    GLint centerPositionLoc;
  37    GLint samplerLoc;
  38
  39    // Texture handle
  40    GLuint textureId;
  41
  42    // Particle vertex data
  43    float particleData[ NUM_PARTICLES * PARTICLE_SIZE ];
  44
  45    // Current time
  46    float time;
  47
  48 } UserData;
  49
  50 ///
  51 // Load texture from disk
  52 //
  53 GLuint LoadTexture ( char *fileName )
  54 {
  55    int width,
  56        height;
  57    char *buffer = esLoadTGA ( fileName, &width, &height );
  58    GLuint texId;
  59
  60    if ( buffer == NULL )
  61    {
  62       esLogMessage ( "Error loading (%s) image.\n", fileName );
  63       return 0;
  64    }
  65
  66    glGenTextures ( 1, &texId );
  67    glBindTexture ( GL_TEXTURE_2D, texId );
  68
  69    glTexImage2D ( GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, buffer );
  70    glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
  71    glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
  72    glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE );
  73    glTexParameteri ( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE );
  74
  75    free ( buffer );
  76
  77    return texId;
  78 }
  79
  80
  81 ///
  82 // Initialize the shader and program object
  83 //
  84 int Init ( ESContext *esContext )
  85 {
  86    UserData *userData = esContext->userData;
  87    int i;
  88
  89    GLbyte vShaderStr[] =
  90       "uniform float u_time;                                       \n"
  91       "uniform vec3 u_centerPosition;                       \n"
  92       "attribute float a_lifetime;                          \n"
  93       "attribute vec3 a_startPosition;                      \n"
  94       "attribute vec3 a_endPosition;                        \n"
  95       "varying float v_lifetime;                            \n"
  96       "void main()                                          \n"
  97       "{                                                    \n"
  98       "  if ( u_time <= a_lifetime )                        \n"
  99       "  {                                                  \n"
 100       "    gl_Position.xyz = a_startPosition +              \n"
 101       "                      (u_time * a_endPosition);      \n"
 102       "    gl_Position.xyz += u_centerPosition;             \n"
 103       "    gl_Position.w = 1.0;                             \n"
 104       "  }                                                  \n"
 105       "  else                                               \n"
 106       "     gl_Position = vec4( -1000, -1000, 0, 0 );       \n"
 107       "  v_lifetime = 1.0 - ( u_time / a_lifetime );        \n"
 108       "  v_lifetime = clamp ( v_lifetime, 0.0, 1.0 );       \n"
 109       "  gl_PointSize = ( v_lifetime * v_lifetime ) * 40.0; \n"
 110       "}";
 111
 112    GLbyte fShaderStr[] =
 113       "precision mediump float;                             \n"
 114       "uniform vec4 u_color;                                       \n"
 115       "varying float v_lifetime;                            \n"
 116       "uniform sampler2D s_texture;                         \n"
 117       "void main()                                          \n"
 118       "{                                                    \n"
 119       "  vec4 texColor;                                     \n"
 120       "  texColor = texture2D( s_texture, gl_PointCoord );  \n"
 121       "  gl_FragColor = vec4( u_color ) * texColor;         \n"
 122       "  gl_FragColor.a *= v_lifetime;                      \n"
 123       "}                                                    \n";
 124
 125    // Load the shaders and get a linked program object
 126    userData->programObject = esLoadProgram ( vShaderStr, fShaderStr );
 127
 128    // Get the attribute locations
 129    userData->lifetimeLoc = glGetAttribLocation ( userData->programObject, "a_lifetime" );
 130    userData->startPositionLoc = glGetAttribLocation ( userData->programObject, "a_startPosition" );
 131    userData->endPositionLoc = glGetAttribLocation ( userData->programObject, "a_endPosition" );
 132
 133    // Get the uniform locations
 134    userData->timeLoc = glGetUniformLocation ( userData->programObject, "u_time" );
 135    userData->centerPositionLoc = glGetUniformLocation ( userData->programObject, "u_centerPosition" );
 136    userData->colorLoc = glGetUniformLocation ( userData->programObject, "u_color" );
 137    userData->samplerLoc = glGetUniformLocation ( userData->programObject, "s_texture" );
 138
 139    glClearColor ( 0.0f, 0.0f, 0.0f, 0.0f );
 140
 141    // Fill in particle data array
 142    srand ( 0 );
 143    for ( i = 0; i < NUM_PARTICLES; i++ )
 144    {
 145       float *particleData = &userData->particleData[i * PARTICLE_SIZE];
 146
 147       // Lifetime of particle
 148       (*particleData++) = ( (float)(rand() % 10000) / 10000.0f );
 149
 150       // End position of particle
 151       (*particleData++) = ( (float)(rand() % 10000) / 5000.0f ) - 1.0f;
 152       (*particleData++) = ( (float)(rand() % 10000) / 5000.0f ) - 1.0f;
 153       (*particleData++) = ( (float)(rand() % 10000) / 5000.0f ) - 1.0f;
 154
 155       // Start position of particle
 156       (*particleData++) = ( (float)(rand() % 10000) / 40000.0f ) - 0.125f;
 157       (*particleData++) = ( (float)(rand() % 10000) / 40000.0f ) - 0.125f;
 158       (*particleData++) = ( (float)(rand() % 10000) / 40000.0f ) - 0.125f;
 159
 160    }
 161
 162    // Initialize time to cause reset on first update
 163    userData->time = 1.0f;
 164
 165    userData->textureId = LoadTexture ( "smoke.tga" );
 166    if ( userData->textureId <= 0 )
 167    {
 168       return FALSE;
 169    }
 170
 171    return TRUE;
 172 }
 173
 174 ///
 175 //  Update time-based variables
 176 //
 177 void Update ( ESContext *esContext, float deltaTime )
 178 {
 179    UserData *userData = esContext->userData;
 180
 181    userData->time += deltaTime;
 182
 183    if ( userData->time >= 1.0f )
 184    {
 185       float centerPos[3];
 186       float color[4];
 187
 188       userData->time = 0.0f;
 189
 190       // Pick a new start location and color
 191       centerPos[0] = ( (float)(rand() % 10000) / 10000.0f ) - 0.5f;
 192       centerPos[1] = ( (float)(rand() % 10000) / 10000.0f ) - 0.5f;
 193       centerPos[2] = ( (float)(rand() % 10000) / 10000.0f ) - 0.5f;
 194
 195       glUniform3fv ( userData->centerPositionLoc, 1, &centerPos[0] );
 196
 197       // Random color
 198       color[0] = ( (float)(rand() % 10000) / 20000.0f ) + 0.5f;
 199       color[1] = ( (float)(rand() % 10000) / 20000.0f ) + 0.5f;
 200       color[2] = ( (float)(rand() % 10000) / 20000.0f ) + 0.5f;
 201       color[3] = 0.5;
 202
 203       glUniform4fv ( userData->colorLoc, 1, &color[0] );
 204    }
 205
 206    // Load uniform time variable
 207    glUniform1f ( userData->timeLoc, userData->time );
 208 }
 209
 210 ///
 211 // Draw a triangle using the shader pair created in Init()
 212 //
 213 void Draw ( ESContext *esContext )
 214 {
 215    UserData *userData = esContext->userData;
 216
 217    // Set the viewport
 218    glViewport ( 0, 0, esContext->width, esContext->height );
 219
 220    // Clear the color buffer
 221    glClear ( GL_COLOR_BUFFER_BIT );
 222
 223    // Use the program object
 224    glUseProgram ( userData->programObject );
 225
 226    // Load the vertex attributes
 227    glVertexAttribPointer ( userData->lifetimeLoc, 1, GL_FLOAT,
 228                            GL_FALSE, PARTICLE_SIZE * sizeof(GLfloat),
 229                            userData->particleData );
 230
 231    glVertexAttribPointer ( userData->endPositionLoc, 3, GL_FLOAT,
 232                            GL_FALSE, PARTICLE_SIZE * sizeof(GLfloat),
 233                            &userData->particleData[1] );
 234
 235    glVertexAttribPointer ( userData->startPositionLoc, 3, GL_FLOAT,
 236                            GL_FALSE, PARTICLE_SIZE * sizeof(GLfloat),
 237                            &userData->particleData[4] );
 238
 239
 240    glEnableVertexAttribArray ( userData->lifetimeLoc );
 241    glEnableVertexAttribArray ( userData->endPositionLoc );
 242    glEnableVertexAttribArray ( userData->startPositionLoc );
 243    // Blend particles
 244    glEnable ( GL_BLEND );
 245    glBlendFunc ( GL_SRC_ALPHA, GL_ONE );
 246
 247    // Bind the texture
 248    glActiveTexture ( GL_TEXTURE0 );
 249    glBindTexture ( GL_TEXTURE_2D, userData->textureId );
 250    glEnable ( GL_TEXTURE_2D );
 251
 252    // Set the sampler texture unit to 0
 253    glUniform1i ( userData->samplerLoc, 0 );
 254
 255    glDrawArrays( GL_POINTS, 0, NUM_PARTICLES );
 256
 257    eglSwapBuffers ( esContext->eglDisplay, esContext->eglSurface );
 258 }
 259
 260 ///
 261 // Cleanup
 262 //
 263 void ShutDown ( ESContext *esContext )
 264 {
 265    UserData *userData = esContext->userData;
 266
 267    // Delete texture object
 268    glDeleteTextures ( 1, &userData->textureId );
 269
 270    // Delete program object
 271    glDeleteProgram ( userData->programObject );
 272 }
 273
 274
 275 int main ( int argc, char *argv[] )
 276 {
 277    ESContext esContext;
 278    UserData  userData;
 279
 280    esInitContext ( &esContext );
 281    esContext.userData = &userData;
 282
 283    esCreateWindow ( &esContext, "ParticleSystem", 640, 480, ES_WINDOW_RGB );
 284
 285    if ( !Init ( &esContext ) )
 286       return 0;
 287
 288    esRegisterDrawFunc ( &esContext, Draw );
 289    esRegisterUpdateFunc ( &esContext, Update );
 290
 291    esMainLoop ( &esContext );
 292
 293    ShutDown ( &esContext );
 294 }