Halo 2 Game Physics Discussion, Q & A

[Grumpy]

Perhaps there are some knowledgeable people on this forum (Twin and Kills?). Anyone can pose game questions here but don't expect an answer unless you describe what it is you are asking/proposing. Be smart about it.

 

I'd like to discuss various game anomalies here so I'll start out with this:

 

@ Kills_Alone and Twinreaper - In a tricking forum where I hang out we have been discussing what we call a Tantrum...in Halo 2. I don't know why it's called a Tantrum but there are times where you can be in the middle of a flat map, just standing there and you jump over and over and suddenly you hit an invisible ledge-like thing while in the air and you can double jump off that or just land and stand there...hovering. Further, there are places in H2 where you stand next to a wall (90 degrees vertical), then jump a bunch of times and eventually you land and float/hover on like a ledge or you can double jump off that ledge. It works on vertical glass too. So, I'd like to get some input on what causes this. The debate centers around what some are calling map collision and they maintain that the feet of MC or Arbiter collides a certain way on a wall map thus producing the 'collision'.

 

This may be true but I always thought that overlapping maps could have something to do with it. Otherwise, when standing on a flat wide open surface, why would you suddenly land on something invisible?

 

1. What causes this?

 

2. Is a wall Tantrum different than a floor tantrum?

 

At first the overlapping map theory might sound bizarre but let me explain. A big part of my tricking career has been learning all the overlapped maps in H2 CMP. When a map is overlapped into another map, you can take an object (crate or such) all the way around to the other map, set it there then go back to the original map and see that crate hoovering somewhere in there. You can overload the map or cause an imbalance that affect later maps.

 

On Quarantine Zone I know there are at least five overlapping maps where I can sit a Spectre in one certain spot and then go to five different maps and see (and use) that same Spectre. On Great Journey I can swordfly up to the ceiling of the level in a certain area and suddenly the map changes and I'm viewing the Cairo Station explosions and then it changes back to GJ. The Cairo, Great Journey, Uprising and High Charity and Gravemind levels are all overlapped and within each other. There may be others.

 

3. When maps overlap, do they create unseen seams where one model passes through another?

 

Personally, I call them string portals, where a doorway like seam is formed where the intersection occurs. Much like 2 bubbles that partially merge, the merging point plane is in both maps at once.

 

4. Within the overlaps, will the invisible model affect the visible model so that an unseen seam/ledge is formed by the intersecting structures?

 

5. Are the people correct who assert that it's a simple geometry map collision thing causing all these phenomenon I've described?

 

Keep in mind I have no understanding whatsoever of map collisions.

 

To all:

If you are interested in answering my or anyone else's questions in-depth but want to see exactly what a Tantrum is and what effects overlapping maps can give I can post vid links.

[Twinreaper]

Hmmm a bit complicated but I can try. Usually whenever you see part of another map that "overlaps", it really isn't an overlap. it's actuall just another BSP from the scenario being displayed as a glitch due to loading zones and triggers. Most of the maps you pointed out, have each's bsp located and called in the scenario file either as a playable portion of the map or part of the cinematic. So that would explain that one.

 

The collision or more directly, the PHMO, Physical Model Collision, is a bit tricky as well. While there are times that havok proves glitchy, this is one of those times. Due to phmo and coll in general having a not so pretty and accurate shape that matches the player model, Havok sometimes cannot predict or accurately place the chief on the map with collision when doing something in a repetative function. Most of the time if you look carefully, you actually see Chief's feet, beign somewhat "stuck" in the ground. meaning that a portion of his feet always seem to be just abrely inside the map. That of coarse is simply the render model only though, not the collision.

 

So anyway, when you jump repeatedly or do something that Havok did not predict or calculate fast enough, it will sometimes place chief on an "invisible" ledge or vertical surface. This is simply because the collision detection did not quickly enough translate chiefs position. For instance, what you describe is also similar to getting through boundaries with vehicles. The collision detection can't quickly enough keep up with Chiefs position after being forcefully rammed, and thus by the time collision detection cathes up, because your model is already on the otherside, Havok then decides that your model is the correct placement, and provides collision to that position...hence putting you safely on the otherside, instead of killing you since you didn't show up inside or against the surface with a vehicle up your bum. At least that is what and how we have always explained it away. I'm sure there is a more accurately technological termination for it...but the older I get, the more I can't remember. LMAO hope that helped?

[Grumpy]

Yeah, thanks, it helped but I'll have to think about the overlap part for a while.

[Grumpy]

Here's another one; xlax007, Duelies and I have all done something on Quarantine Zone that I don't understand.

 

The trick was to get a vehicle onto the moving Gondola as it glides toward the tunnels. I took a Spectre and launched it from above the entrance to the Gondola dock. I launched it toward the Library picture in the distance and I had the other player trip the lz below and instead of hitting the boundary barrier, I flew through it. As the Spectre was flying I raced up the ramps to the Gondola and activated the cutscene and after that I spawned on the Gondola and that same Spectre landed above me.

 

So...when I launched I went through a loadzone, then I flew through a cutscene and then after I spawned on the Gondola the Spectre was still in the air.

 

The question; how the hell did this happen? How does the programming cover something like this? It went through a damned cutscene still flying through the maps! We've never known exactly how a vehicle/object can leave one map, wind up in another map entirely after going through a cutscene and land.

 

This shows the landing on the beam:

 

This shows that the Gondola formed and caught the Spectre like a catchers mitt:

[Twinreaper]

I can't exactly see where the spectre is it in relation to the loading zone or the end of the level itself, so I will take a guess. Seeing as how you were more than likely above the end of the level with your back facing the loading zone/cinematic trigger, I can only assume that everything was spawned to the other players location.

 

When you spawn at a distance greater than usual Line of Site, you are not teleported inside your vehicle, but instead teleported next to the other player. Sometimes if your close enough to the other person your vehicle is teleported with you...we have seen this before many times.

 

I can only surmize, that because the spectre was launched passed the loading zone, that it landed on the other side of the loading zone. So when the level re-loaded the new bsp, it also loaded the spectre because the engine detected the vehicle inside of it, instead of the previous bsp. It's kinda like taking a vehicle thru different bsp's of the level. Even though the level loads another section of the map, the vehicle remains. The only time this fails is if the newer loaded/post cinematic, spawns the player away from the area in which the vehicle was, making backtracking impossible. A good example of this, is the banshee on the last level. Even though a cutscene plays, the banshee is still in an area where the player spawns initially. I hope that made sense..lmao

 

Additionally, the only reason you are able to do these kinds of things, is because the engine itself loads vehicles and weapons from the shared/mainmenu/single_player_shared resource files. In Halo 3 and Reach, if the vehicle itself does not spawn on a particular section or is located in the map file itself as a reference, you expereince losing vehicles as in they just plain dissapear when a new section is loaded. Halo 2 does the opposite and loads the vehicle and wepaons or whatever, as long as the said item is still present and in play, regardless of reference within the map file.

[Grumpy]

I can't exactly see where the spectre is it in relation to the loading zone or the end of the level itself, so I will take a guess. Seeing as how you were more than likely above the end of the level with your back facing the loading zone/cinematic trigger, I can only assume that everything was spawned to the other players location.

 

When you spawn at a distance greater than usual Line of Site, you are not teleported inside your vehicle, but instead teleported next to the other player. Sometimes if your close enough to the other person your vehicle is teleported with you...we have seen this before many times.

 

I can only surmize, that because the spectre was launched passed the loading zone, that it landed on the other side of the loading zone. So when the level re-loaded the new bsp, it also loaded the spectre because the engine detected the vehicle inside of it, instead of the previous bsp. It's kinda like taking a vehicle thru different bsp's of the level. Even though the level loads another section of the map, the vehicle remains. The only time this fails is if the newer loaded/post cinematic, spawns the player away from the area in which the vehicle was, making backtracking impossible. A good example of this, is the banshee on the last level. Even though a cutscene plays, the banshee is still in an area where the player spawns initially. I hope that made sense..lmao

 

Additionally, the only reason you are able to do these kinds of things, is because the engine itself loads vehicles and weapons from the shared/mainmenu/single_player_shared resource files. In Halo 3 and Reach, if the vehicle itself does not spawn on a particular section or is located in the map file itself as a reference, you expereince losing vehicles as in they just plain dissapear when a new section is loaded. Halo 2 does the opposite and loads the vehicle and wepaons or whatever, as long as the said item is still present and in play, regardless of reference within the map file.

The vehicle was still flying so I'm still confused. If you watch the first vid closely, P1 is launching while P2 sits at the lz, then just after launch P2 crosses the lz (with P1 spawning right there at the lz) then races up the ramp to activate the cutscene, then, when I spawn on the Gondola, I look over and the Spectre is landing. xlax007 has a better vid where he shows his Spectre flying in, same with Duelies, you could see the vehicle flying at you from a good distance. So it still had the impetus that the launch gave it. That's what confuses me, it's not just a simple teleport since it's flying from the launch before, during and after the cutscene. Also, P1 spawned at the lz where P2 was after the lz was hit, so if the vehicle was tied to P1 because he was inside it, why would the vehicle not port at that time? When P2 ran up the ramp and activated the cutscene, P1 had been out of the Spectre. Then when I appeared on the Gondola the Spectre comes flying in. Sorry, I'm still confused.

 

Edit: After thinking about what you said, I guess the Spectre was ported to the Gondola canyon when the lz was tripped...then it did go through the cutscene because it's also in the same canyon...rhen when the cutscene was over the Spectre finished it's trip.

 

I think I understand now, thanks.