Could you write about the rotating red sphere thing on AIZ1 (Sonic 3 alone debug)? Did that have any purpose other than destroy the game´s palette and framerates?Directly after the surfboarding Sonic object, Angel Island Zone 1's debug reel once again treats us to an unusual sprite: a set of red spheres revolving around each other in three dimensions:
What on earth could be the purpose of this object? Here's what I conjectured when I was just a kid: it's only available in AIZ1's debug reel, it comes right after the surfboard, it's red and it messes with the HUD once it's placed. It must be the early equivalent of the cutscene Knuckles object! I was a dumb kid.
The truth makes considerably more sense: it is a test of the 3D sprite effect seen in the game's special stages. The fact that the object is part of AIZ1's debug reel seems to be entirely circumstantial; it was likely added to the first level of the game simply for ease of access. However, its origins in the special stage become evident when we look up the location of its graphics within the ROM:
| Name | Address |
|---|---|
| ArtUnc_SStageTailstails | 0909E8 |
| Map_SStageTailstails | 0910E8 |
| PLC_SStageTailstails | 091106 |
| ArtNem_SphereTest | 0911CE |
| ArtNem_SStageShadow | 091B2E |
| ArtNem_GetBlueSpheres | 091B70 |
| ArtNem_GBSArrow | 091CF2 |
The object's overall behavior can actually be controlled by player 2. The controls, although a tad obtuse, are as follows:
- Down/Left: moves the object up and down
- Up/Right/B: toggles the rotation of each axis
- A/C: shrinks/enlarges the object
- Start: toggles between automatic and manual rotation
No doubt owing to its roots, the sphere test object stores its movement and rotation state in a region of RAM starting at address $E400, which is used by the special stage for the same purpose. In the main game however, the same area is used to maintain a buffer of the player's last few positions. As a result, exiting debug mode and moving around will very quickly make the object become all kinds of messed up.
Does it use software scaling?
ReplyDeleteNo, it uses a bunch of sprites pre-rendered at various sizes, just like the the special stage.
DeleteThe Genesis VDP cannot scale graphics. The 32X and SNES can, however.
Delete...Hence software scaling.
DeleteWhat does "Eosian" even mean?
ReplyDeleteThat last sentence does explain why the controls were weird for me, so thanks.
No idea where the term comes from. Don't take the post titles too seriously.
DeleteIdk
DeleteSince you have covered the Surfboard and the Rotating spheres, could you talk about the "Eggman flying away" sprites?
ReplyDeletePatience, little one.
DeleteHeh. Looking back through the blog as I do every now and then, and I can't help but smile reading this post - I never would've imagined that we'd one day actually *have* a proto showing the special stage test sphere in its "intended" habitat, as it were!
ReplyDeleteI mean, sure, the location of the graphics in the ROM combined with the nature of the object itself pretty much confirm it was a special stage test, but it's still pretty fantastic to actually be able to see it in action.
There’s a lot of pallets glitches for the rings. Can you talk about those
ReplyDelete