What was the first 3D Sonic game

Sonic adventure for the dreamcast was the first sonic game(sonic 3d blast does not count as a 3d sonic game),sonic adventure was very successful and alot of people loved it and bought it,there was also a port to the gamecube called sonic adventure DX directors cut which was also very successful and alot of people loved it and bought it,the only difference between the dreamcast version and the gamecube version is thats the graphics are better on the gamecube version,on the gamecube version you could unlock metal sonic and on the gamecube version there were extra levels