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Several additions/changes were made to Sonic Adventure DX: Director's Cut when it was ported to the Nintendo GameCube and PC. They include:
- Enhanced graphics: The main characters were re-created with higher polygon counts, resulting in smoother models. Shader technology was also implemented for effects like rippling water (shader effects are not present in the PC version). There are some new high-resolution textures, but some of the new textures are blurry. The textures are very different overall, though not everyone would agree that they are better. An example of a very different look is the top floor of Hot Shelter (area 1, where Amy and Big start). Originally, the room was dark, with a green glow, and machinery in the background. It is much brighter now, with flat blue-grey walls and the Robotnik symbol replacing the machinery.
- The original 60fps frame rate was partially restored. Unfortunately due to the unstable nature of the Sonic Adventure engine, the frame rate frequently fluctuates between 60fps, 30fps, and sometimes, even 20fps.
- Changes (mostly minor) were made within the levels themselves in an effort to help patch some of the game's problems concerning collision detection. However, many glitches were not fixed, and many were actually added. It's possible that the GameCube version has even more glitches than the Dreamcast version.
- The Internet connection feature was removed. However, most of the downloadable content from the Dreamcast version was included in the GameCube port, but may only be accessed via Action Replay cheats.
- A brand-new "Free Camera" mode was added, allowing you to move and adjust the Camera with the GameCube's during play, similar to the system used in Super Mario Sunshine. Unfortunately, the camera mode goes back to "Auto Camera" (or the camera options disappear) when an area is loaded, in some stages or parts of stages, and in random places where the instructions for the Auto Camera may be overriding the "Free Camera".
- Many changes to the Chao System were made, including removing the Chao Adventure VMU minigame (instead replaced with a Game Boy Advance connection feature). Additionally, the Chao Raising engine and models from Sonic Adventure 2: Battle were adapted and used. In fact, Chao from SA2:B may be imported into SA:DX using the Game Boy Advance.
- 60 Missions were added for an all-new Mission Mode, which tasks the player with completing certain goals within the Adventure Fields and Action Stages for Emblems, similar to the Mission Mode found in Sonic Jam's 3D Sonic World.
- A reward for collecting all the Emblems was added: the option to play as Metal Sonic, who, despite new sound effects, some different animations (including that he can't stand up straight, due to a glitch) and a new player model, plays exactly like Sonic, and is only available in Time Trial and boss mode.
- Cream the Rabbit makes several cameo appearances during the main game and Mission Mode, such as being the one who drops the Ice Key.
- In the Dreamcast version, E-102 Gamma's Adventure Field was playable at night after beating his story. This seems to randomly happen in the GameCube version. What actually causes it is unknown. Strangely, the PC version follows the Dreamcast version by having the Adventure Fields always playable at night.