Monday, March 5, 2012

New splitscreen approach.

As posted here, I implemented a splitscreen mode for the engine.
The implementation is sort of dirty as all graphics are getting recreated per camera.

For instance: you want to draw a graphic with 4 player split screen.The graphic will then get created 3 times (1 graphic for each camera). That ensures that every camera has its own graphic with which it can do what ever it wants (like zoom, rotation, etc.)

As you can imagine, that is quite expensive and for many graphics on screen pretty memory consuming.
That seemed like a wasteful but working implementation until now.

It's just theoretical, but I'm pretty sure it is possible to reimplement it so that every graphic will only get drawn only for one camera per tick. If there's more than one camera, the graphic will get drawn for the next camera the next frame.

It'll go like this (C style pseudocode):

 void draw(IGraphic graphics*[]){  
           CURRENT_CAMERA = 1;               // Start from first camera  
      for(int i = 0;i < AMOUNT_GRAPHICS;i++){ //go through all graphics.  
           m_cameras[CURRENT_CAMERA]->draw(graphics[i]); //draw graphics into buffer of the current camera  
      CURRENT_CAMERA++; //Increment to camera counter and leave the draw function.  

So if the game uses 3 cameras it'll look like this:

Frame 1 : Draw graphics for camera 1
Frame 2 : Draw graphics for camera 2
Frame 3 : Draw graphics for camera 3

Frame 4 : Draw graphics for camera 1
Frame 5 : Draw graphics for camera 2
Frame 6 : Draw graphics for camera 3

I don't know if this implementation will cause a big delay, but I guess it's for me to find out ;)

This approach will obviously split the FPS in half.
e.g. 60FPS / 2 Cameras = 30 FPS per camera.

That means that the game needs to run with ~120 FPS to look smooth with 4 cameras....
Shouldn't be a problem with a 2D game.

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