src/glsl/blinking-teapot.c

   1 /**
   2  * blinking-teapot demo. It displays a teapot whose color go from blue to pink.
   3  * The color variation is handled by uniform buffer object.
   4  * Sources mostly from http://www.jotschi.de/?p=427 which uses UBO SPEC example
   5  *
   6  * Vincent Lejeune 2011
   7  */
   8
   9 #include <stdio.h>
  10 #include <stdlib.h>
  11 #include <string.h>
  12 #include <GL/glew.h>
  13 #include "glut_wrap.h"
  14 #include "shaderutil.h"
  15
  16
  17 static int mouse_old_x, mouse_old_y;
  18 static int mouse_buttons = 0;
  19 static float rotate_x = 0.0, rotate_y = 0.0;
  20 static float translate_z = -2.0;
  21
  22 static float delta = 0.01;
  23 static GLfloat wf, hf;
  24
  25
  26 static const GLchar *names[] = { "SurfaceColor", "WarmColor", "CoolColor",
  27   "DiffuseWarm", "DiffuseCool"
  28 };
  29
  30 static GLuint buffer_id, uniformBlockIndex, uindex, vshad_id, fshad_id,
  31   prog_id;
  32
  33 static GLsizei uniformBlockSize;
  34 static GLint singleSize;
  35 static GLint offset;
  36
  37 static const GLfloat colors[] =
  38   { 0.45, 0.45, 1, 1, 0.45, 0.45, 1, 1, 0.75, 0.75, 0.75, 1,
  39   0.0, 0.0, 1.0, 1, 0.0, 1.0, 0.0, 1,
  40 };
  41
  42 static GLfloat teapot_color = 1;
  43
  44 static void
  45 reshape (int w, int h)
  46 {
  47   wf = (GLfloat) w;
  48   hf = (GLfloat) h;
  49   glMatrixMode (GL_PROJECTION);
  50   glLoadIdentity ();
  51   gluPerspective (60.0, wf / hf, 0.1, 100.0);
  52 }
  53
  54 static void
  55 init_opengl (void)
  56 {
  57
  58   if (!ShadersSupported ())
  59     exit (1);
  60
  61   if (!glutExtensionSupported("GL_ARB_uniform_buffer_object")) {
  62      printf("GL_ARB_uniform_buffer_object is required.\n");
  63      exit(1);
  64   }
  65
  66   vshad_id = CompileShaderFile (GL_VERTEX_SHADER, "blinking-teapot.vert");
  67   fshad_id = CompileShaderFile (GL_FRAGMENT_SHADER, "blinking-teapot.frag");
  68   prog_id = LinkShaders (vshad_id, fshad_id);
  69
  70   UseProgram (prog_id);
  71
  72   reshape (680, 400);
  73
  74   glGenBuffers (1, &buffer_id);
  75
  76   glBindBuffer (GL_UNIFORM_BUFFER, buffer_id);
  77   glBufferData (GL_UNIFORM_BUFFER, uniformBlockSize, NULL, GL_DYNAMIC_DRAW);
  78
  79   glBindBufferBase (GL_UNIFORM_BUFFER, 0, buffer_id);
  80   glUniformBlockBinding (prog_id, uniformBlockIndex, 0);
  81
  82   glGetUniformIndices (prog_id, 1, &names[2], &uindex);
  83
  84   glGetActiveUniformsiv (prog_id, 1, &uindex, GL_UNIFORM_OFFSET, &offset);
  85   glGetActiveUniformsiv (prog_id, 1, &uindex, GL_UNIFORM_SIZE, &singleSize);
  86
  87   glViewport (0, 0, 680, 400);
  88   glBufferData (GL_UNIFORM_BUFFER, 80, colors, GL_DYNAMIC_DRAW);
  89 }
  90
  91 static void
  92 render (void)
  93 {
  94   glClearColor (0.0, 0.0, 0.0, 0.0);
  95   glClear (GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
  96   glUseProgram (prog_id);
  97   glEnable (GL_DEPTH_TEST);
  98
  99   glMatrixMode (GL_MODELVIEW);
 100   glLoadIdentity ();
 101   glTranslatef (0.0, 0.0, translate_z);
 102   glRotatef (rotate_x, 1.0, 0.0, 0.0);
 103   glRotatef (rotate_y, 0.0, 1.0, 0.0);
 104   glColor3f (1.0, 1.0, 1.0);
 105
 106   glBindBuffer (GL_UNIFORM_BUFFER, buffer_id);
 107   glBufferSubData (GL_UNIFORM_BUFFER, offset, 4 * singleSize, &teapot_color);
 108
 109   glFrontFace (GL_CW);
 110   glutSolidTeapot (0.6);
 111   glFrontFace (GL_CCW);
 112   glutSwapBuffers ();
 113   glutPostRedisplay ();
 114
 115   teapot_color += delta;
 116
 117   if (teapot_color > 1.0)
 118     {
 119       delta = -0.01;
 120     }
 121
 122   if (teapot_color < 0.0)
 123     {
 124       delta = +0.01;
 125     }
 126
 127 }
 128
 129 static void
 130 mouse (int button, int state, int x, int y)
 131 {
 132   if (state == GLUT_DOWN)
 133     {
 134       mouse_buttons |= 1 << button;
 135     }
 136   else if (state == GLUT_UP)
 137     {
 138       mouse_buttons = 0;
 139     }
 140
 141   mouse_old_x = x;
 142   mouse_old_y = y;
 143   glutPostRedisplay ();
 144 }
 145
 146 static void
 147 motion (int x, int y)
 148 {
 149   float dx, dy;
 150   dx = x - mouse_old_x;
 151   dy = y - mouse_old_y;
 152
 153   if (mouse_buttons & 1)
 154     {
 155       rotate_x += dy * 0.2;
 156       rotate_y += dx * 0.2;
 157     }
 158   else if (mouse_buttons & 4)
 159     {
 160       translate_z += dy * 0.01;
 161     }
 162
 163   mouse_old_x = x;
 164   mouse_old_y = y;
 165 }
 166
 167 int
 168 main (int argc, char **argv)
 169 {
 170   glutInit (&argc, argv);
 171   glutInitWindowSize (400, 400);
 172   glutInitDisplayMode (GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
 173   glutCreateWindow ("UBO Example");
 174
 175   glutDisplayFunc (render);
 176   glutMouseFunc (mouse);
 177   glutMotionFunc (motion);
 178   glewInit ();
 179   init_opengl ();
 180   glutMainLoop ();
 181   return 0;
 182 }