No clipping question

[CacoDoomer]

I have been wondering this for years. Does anyone know why when you walk too far away from the map using no clipping the game starts to generate textures and sometimes enemy sounds? You also come to the other side of the level if you go far enough.

[Quasar]

CacoDoomer said:

I have been wondering this for years. Does anyone know why when you walk too far away from the map using no clipping the game starts to generate textures and sometimes enemy sounds? You also come to the other side of the level if you go far enough.

Integer overflow, of varying types.

As you near the outer limits of Doom's coordinate system, the results of operations such as R_PointToAngle, R_PointOnSide, R_PointInSubsector, P_AproxDistance, P_CheckMeleeRange, etc. begin to malfunction, as they must do intermediate additions and multiplications that overflow the range of fixed_t, which is an effective -32768 to 32767 units. They return a very short distance instead of a large one when this happens.

This makes you see strange and otherwise impossible things, experience strange nightmarish looking glitches, and also frequently puts you within attack range of every living monster on the map.

[dew]

here's all of that crazy behaviour in one demo by grazza.

[Memfis]

Is it possible to get to the edge of the void, start shooting with rocket launcher at a wall/monster and kill all monsters on the map with splash damage?

[dew]

Memfis said:

Is it possible to get to the edge of the void, start shooting with rocket launcher at a wall/monster and kill all monsters on the map with splash damage?

there are no monsters to shoot at there, so it's reduced to just walls. i just tested it and it seems you can't afflict the monsters in any way. neither your own melee, nor rocket splash hurts anything at the edge of the map space.

[Memfis]

Aww, it would be funny to max some bigass map in a few minutes. Oh well, thanks for testing this. :)

[Grazza]

You might be able to provoke infighting by that method. In my Pit demo linked above, I seem to recall some of the monsters that tried to tele-attack me fired projectiles, and I think there was a death from infighting. (I can't readily confirm that right now, as I am away from home, with a Doomless computer.)

If you worked out which parts of the "seam" were related to which sectors, you could presumably start infighting in several places. But to make it a valid Max, you'd need to break back into the map to finish off the survivors and (for most maps) to exit. TBH, I think it's more realistic to construct a map with this in mind than it is to stumble across one where it is a viable strategy.