Laggy 2-Player split screen problem!

[ChrisStreet]

For my game, Mr Stumps 2, I have been working on the split-screen multiplayer mode, but I've been having a bit of trouble in regards to the sending of data.

To create the split-screen I'm simply using two sub-app objects and sharing 8 Global Values between them.

The two sub-apps contain a cloned frame, but each has a different playable character: The first subapp has Mr Stump (Player 1), the second contains Dr Braceface (Player 2). I've created ghost versions of the characters too, so Player2's position, for example, can be seen in Player1's subapp frame. Not dissimilar to Sonic 2/3 on Megadrive/Genesis.

The Global values represent:

Sub-App 1(Player 1)

Mr Stump's X Position
Mr Stump's Y Position
Mr Stump's Direction
Mr Stump's Animation Frame

(the ghost Mr Stump that appears on Player2's frame recieves the data)

and (Subapp2 - Player 2)

Dr Braceface's X Position
Dr Braceface's Y Position
Dr Braceface's Direction
Dr Braceface's Animation Frame

(the ghost Dr Braceface that appears on Player1's frame recieves this particular data)

However, there is noticeable lag between key presses. Even with fastloop there doesn't appear to be a way to keep the ghost version of the players in sync with the "real" players. Could anyone possibly please help or advise me on this issue? Would it be easier to load the positions via an array?

[Joshtek]

You might want to check out my True Split Screen Example, which uses multiple Viewport objects. It uses LIJI's technique of setting the window size large in MMF2 then making it smaller using the Window Control Object, thus making the MMF2 runtime render the off-window portion of the screen so as to make it accessible to the Viewport object. Obviously because this overrides MMF2's usual efficiencies, you may wish to make objects which are out of the sight of either player invisible or something to reduce the strain on the runtime engine.

[LB]

Are you using Moo? Or just sub-apps and/or shared data?

If you are using sub-apps, then you should know that it's trouble with the sub-app feature. I suggest using two applications with shared data objects.

[ChrisStreet]

I was just using Sub-Apps and Global values to store the data. I tried out the Viewport split-screen example, it's a nice idea, but I'm going to have to completely clone my entire game engine for both characters... I can't say I fancy doing that

[stuckboy]

If the worst comes to the worst you could try some kind of dead reckoning solution.

eg. Instead of sending Dr Braveface's X position, you send Dr Braveface's X position + Dr Braveface's X velocity.

This way, if your ghost player is 1 frame behind the actual player then the engine will predict his actual position pretty accurately.

You might have to make a system that stops the ghost player from clipping through a backdrop though; when a player lands from a jump they may momentarily flick into the ground below due to their high velocity when landing from a jump.

[ChrisStreet]

I hadn't thought of trying that, actually. I'll give that a go - thanks!