public static Matrix4X4 MakeLookAt(Vector3 eye, Vector3 center, Vector3 up)
{
Matrix4X4 ret = new Matrix4X4(null);
float eyex = eye.Elements[0],
eyey = eye.Elements[1],
eyez = eye.Elements[2],
upx = up.Elements[0],
upy = up.Elements[1],
upz = up.Elements[2],
centerx = center.Elements[0],
centery = center.Elements[1],
centerz = center.Elements[2];
float z0, z1, z2, x0, x1, x2, y0, y1, y2, len;
//vec3.direction(eye, center, z);
z0 = eyex - center.Elements[0];
z1 = eyey - center.Elements[1];
z2 = eyez - center.Elements[2];
// normalize (no check needed for 0 because of early return)
len = 1 / Math.Sqrt(z0 * z0 + z1 * z1 + z2 * z2);
z0 *= len;
z1 *= len;
z2 *= len;
//vec3.normalize(vec3.cross(up, z, x));
x0 = upy * z2 - upz * z1;
x1 = upz * z0 - upx * z2;
x2 = upx * z1 - upy * z0;
len = Math.Sqrt(x0 * x0 + x1 * x1 + x2 * x2);
if (len == 0) {
x0 = 0;
x1 = 0;
x2 = 0;
} else {
len = 1 / len;
x0 *= len;
x1 *= len;
x2 *= len;
};
//vec3.normalize(vec3.cross(z, x, y));
y0 = z1 * x2 - z2 * x1;
y1 = z2 * x0 - z0 * x2;
y2 = z0 * x1 - z1 * x0;
len = Math.Sqrt(y0 * y0 + y1 * y1 + y2 * y2);
if (len == 0) {
y0 = 0;
y1 = 0;
y2 = 0;
} else {
len = 1 / len;
y0 *= len;
y1 *= len;
y2 *= len;
}
ret.Elements[0] = x0;
ret.Elements[1] = y0;
ret.Elements[2] = z0;
ret.Elements[3] = 0;
ret.Elements[4] = x1;
ret.Elements[5] = y1;
ret.Elements[6] = z1;
ret.Elements[7] = 0;
ret.Elements[8] = x2;
ret.Elements[9] = y2;
ret.Elements[10] = z2;
ret.Elements[11] = 0;
ret.Elements[12] = -(x0 * eyex + x1 * eyey + x2 * eyez);
ret.Elements[13] = -(y0 * eyex + y1 * eyey + y2 * eyez);
ret.Elements[14] = -(z0 * eyex + z1 * eyey + z2 * eyez);
ret.Elements[15] = 1;
return ret;
}
