Function MakeNewTexture

demos/glthreadsint.c:135–175

static void
MakeNewTexture(struct winthread *wt)
{
#define TEX_SIZE 128
   static float step = 0.0;
   GLfloat image[TEX_SIZE][TEX_SIZE][4];
   GLint width;
   int i, j;

   for (j = 0; j < TEX_SIZE; j++) {
      for (i = 0; i < TEX_SIZE; i++) {
         float dt = 5.0 * (j - 0.5 * TEX_SIZE) / TEX_SIZE;
         float ds = 5.0 * (i - 0.5 * TEX_SIZE) / TEX_SIZE;
         float r = dt * dt + ds * ds + step;
         image[j][i][0] =
         image[j][i][1] =
         image[j][i][2] = 0.75 + 0.25 * cos(r);
         image[j][i][3] = 1.0;
      }
   }

   step += 0.5;

   glBindTexture(GL_TEXTURE_2D, TexObj);

   glGetTexLevelParameteriv(GL_TEXTURE_2D, 0, GL_TEXTURE_WIDTH, &width);
   if (width) {
      assert(width == TEX_SIZE);
      /* sub-tex replace */
      glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, TEX_SIZE, TEX_SIZE,
                   GL_RGBA, GL_FLOAT, image);
   }
   else {
      /* create new */
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

      glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, TEX_SIZE, TEX_SIZE, 0,
                   GL_RGBA, GL_FLOAT, image);
   }
}