Argh, I wanna become Betatester too.

Quote from Razzone :

Infact I was discussing about PHYSICAL DATA and the "Definitely no.." referred to physical data contained in SPRs.

1. Physical data != physics data.
Physical data are some paper files you put in a folder, physics data referred to parts of the LFS physics engine - which is not contained in the replays. Of course the setups are included too, but thinking more like a programmer I filed that under "user input".

2. My reply "Definitely no." was the direct answer to his question "Will the replays of today still work with the new patch?". Nothing else.


So in conclusion: read - comprehend - post. Thanks.

Quote from Gentlefoot :

Cool - cos I reckon a lot of my PBs are gonna be smashed if there's a load more low speed grip.

I expect WRs to be lower in some tracks after the patch. If patch does what it should do it's not possible to anymore use the sliding as advantage when making WRs if you know what I mean.

Quote from AndroidXP :

While viewing the replay, these inputs are fed into the physics engine, thus relying on the physics engine to give the same results as it did when the race was being recorded.

Are you really 100% sure about that? I mean did the devs ever confirm that replays work like this?

Because IMHO that wouldn't work - at least for MPRs. Since an internet connection is not always 100% stable you can never be sure to receive all the input data from all clients. So if you only use the input data to re-play the race it would go OOS everytime somebody lags or a packet loss occurs or something. And if you ever looked from the cockpit view in an MPR you will have seen that the steering wheel doesn't move smooth like in SPRs but in steps. And if this represents the input data used to re-create the path everybody was driving it would go OOS at once since you don't have all the input you would need for the "real" way that was driven.

So if my assumption (and remember, it's nothing more than that) is right it seems logical to me, that a replay can only be replayed correctly if you use the location- and direction-data of the whole car to re-create the driving path and the input-data to simulate the appropriate steering wheel movement and such. In this case, even when a lag occurs the replayed car can be placed correctly again after the lag which wouldn't be possible with only the input data since the game cannot know what the driver was doing during the lag. And I saw lagging cars not going OOS in replays. And another consequence would be that as long as the 3D-data of the track and the car doesn't change, the replays would still work.

Just my thoughts - tell me if you know that I'm wrong.

Seidel, SPRs are very strict and recorded but MPRs arent. MPRs are based on interpolation.

MPR replays can handle small differences because it just sets the car to the recorded state and lets the physics engine roll it in the direction it was heading for a while, and then totally forgets everything and changes the car to the next recorded state. Altough the recorded physics engine (older) is different than the interpolation engine (newer), it will only make the car move a little different in between the updates.
Some stuttering during corners here and there, some small warps forwards or backwards while accelerating and things like that.

An SPR replay has every state( change) of the car recorded on every moment. It does not use interpolation and it needs a physics engine to build and calculate on. If the physics engine is just a bit different, imagine what effect it would have after 10 updates > after 100 updates etc.

OOS!

(I'm not completely sure of this information but I think it's just about reliable.)

Quote from Christian Seidel :

Are you really 100% sure about that?

Pretty much yes, but read what I've written in my original reply

Quote from AndroidXP :

...but only the user inputs for SPR files or the position/user-input packets for MPR files...

When you race online, all you get is a constant stream of position and "user input state" packets from the server. Such a packet contains the position of the car, the forces acting on it and the current user input, like "steer 1.54° to right" and "throttle at 85%".

All LFS now does is take the packet, put the car on the position and input the rest to the physics engine, hoping that the result somewhat resembles what happens in real. This goes on until the next packet for this car is received, putting the car to the correct position where it really was on the driver's PC.

This are the little jumps you constantly see in a MP race, everytime correcting the little inaccuracies between what you calculated and what happend on the PC of the driver. It's most apparent in crashes, where sometimes you see the competitor's car fly around and suddenly it's planted on the ground again, simply because crashes have the highest degree of randomness right now.


Now, what happens when you record and view a multiplayer race is basically that you store all those input packets and then "play them back", as if there's a server sending you those same packets again. The only difference is, that this now also goes also for your car so you can even see the jumping on your own car.

The point is, between those packets, you also use the physics engine. If the latter one changes, this would basically result in bigger correction-jumps, depending on how much the behaviour changed, up until a point where it's simply impossible to watch it because of 2 metre jumps every view seconds.


In conclusion, with a new physics engine:
- SPR files are completely broken
- MPR files should work to a certain degree, but that also depends on what content you need from a MPR packet. If there's some info missing that is vital for the new engine, then you won't be happy either. Scawen may also just make a compability/version check and simply refuse replaying "old" replays. Then MPR would be "completely broken", too.