int perm[256]= {151,160,137,91,90,15,
		131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23,
		190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33,
		88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166,
		77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244,
		102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196,
		135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123,
		5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42,
		223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,172,9,
		129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,97,228,
		251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107,
		49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254,
		138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180};

/* These are Ken Perlin's proposed gradients for 3D noise. */
int grad3[16][3] = {{0,1,1},{0,1,-1},{0,-1,1},{0,-1,-1},
		{1,0,1},{1,0,-1},{-1,0,1},{-1,0,-1},
		{1,1,0},{1,-1,0},{-1,1,0},{-1,-1,0}, // 12 cube edges
		{1,0,-1},{-1,0,-1},{0,-1,1},{0,1,1}}; // 4 more to make 16


/*
 * initPermTexture(GLuint *texID) - create and load a 2D texture for
 * a combined index permutation and gradient lookup table.
 * This texture is used for 2D and 3D noise, both classic and simplex.
 */
void initPermTexture(GLuint *texID)
{
	char *pixels;
	int i,j;

	glGenTextures(1, texID); // Generate a unique texture ID
	glBindTexture(GL_TEXTURE_2D, *texID); // Bind the texture to texture unit 0

	pixels = (char*)malloc( 256*256*4 );
	for(i = 0; i<256; i++)
		for(j = 0; j<256; j++) {
			int offset = (i*256+j)*4;
			char value = perm[(j+perm[i]) & 0xFF];
			pixels[offset] = grad3[value & 0x0F][0] * 64 + 64;   // Gradient x
			pixels[offset+1] = grad3[value & 0x0F][1] * 64 + 64; // Gradient y
			pixels[offset+2] = grad3[value & 0x0F][2] * 64 + 64; // Gradient z
			pixels[offset+3] = value;                     // Permuted index
		}

	// GLFW texture loading functions won't work here - we need GL_NEAREST lookup.
	glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, 256, 256, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixels );
	glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );
	glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );
}