Weaknesses in the Ultima IX Physics

Weaknesses in the Ultima IX Physics demonstrates the problems the physics engine of Ultima IX encounters, which are quite a number.

Gravity Trouble
The gravity engine in the game is very badly written. Essentially, items initially try to follow the call of gravity, but if there's anything preventing a perfect fall, the item just gives up on pretending that gravity exists and just sits there. That's because the programmers didn't have the time to program a real gravity engine without taxing the game, which already was at its limit anyway with everything that needed to be calculated. So whenever something is not going perfectly during the fall, the object just ignores gravity.

The effects are quite interesting. Monster drops and/or their remains just hover in the air or seem to be glued to some other object and the scenery (like a slope) in the most strange ways possible. The same goes for dropped objects. Some have misused this broken physics engine for hilarious effect, like building bridges over the ocean with various objects.

The Floating Rune
In addition to that, a very well known problem is, that after cleaning a shrine, nowadays, the Rune and Sigil just hover high above the shrine instead of dropping down as they should. The above described behaviour is mixed with another badly written script that breaks when exposed to faster computers. The only chance to get them back if that happens is to either shoot them down with a Fireball, or to use the fly cheat to reach them.

Forgotten World Team's Note on issue: The actual problem with the floating Rune and Sigil is related to the game not rendering/loading the objects in active memory for gravity to be calculated when these objects are made visible above the shrine. This issue seems to be corrected with enlarging the view distance.



Climbing onto the Scenery
NPCs and enemies often have the strange habit to suddenly appear standing on top of other objects like desks, chairs or chests. This not only looks very strange, but sometimes can even break their AI or have other bad consequences for the scripting in the game.

Two reasons for this bizarre behaviour exist:


 * The pathfinding engine was never really developed, since it was decided that all NPCs stay stationary throughout the entire game and most get teleported if the need would arise. This of course meant that if one still has to move, even a little, it was prone to cause unintended effects.


 * The Z (height) control of the engine isn't the very best, as noted above. This also affects NPCs, but with different symptoms, in that their movements sometimes ignore the Z component and thus they "jump" onto said objects when their place in the world is calculated when entering the area.

Falling through the Ground
This problem haunted the early versions of the game and though patches exist, the programmers never fully managed to get rid of it. Essentially, there's always a chance that the Avatar drops through the floor when the collision detection malfunctions and manages to end up below the game world, standing in a sort of black void. Looking up reveals the game world with a transparent ground (as there's no ground texture on the underside). This pretty much means a reload, as there's no chance to return to normal gameplay.

This can also happen to characters and even if they sink only a little, their AI gets damaged beyond repair. 