Fading day/night

[AnasAbdin]

Hi all,

I have two backgrounds for a room, (0 = day, 1 = night )
I can change between them using SetBackgroundFrame.

However, I found this code extract in the manual:

Code: ags

DrawingSurface *mainBackground = Room.GetDrawingSurfaceForBackground(0);
DrawingSurface *nightBackground = Room.GetDrawingSurfaceForBackground(1);
mainBackground.DrawSurface(nightBackground, 50);
mainBackground.Release();
nightBackground.Release();

I am trying to make the day background fades into night. The manual says:

TIP: If you want to gradually fade in a second background, create a copy of the original surface and then restore it after each iteration, otherwise the backgrounds will converge too quickly.

I'm not sure what I'm doing wrong, it is working exactly as the manual warned: (otherwise the backgrounds will converge too quickly)

Code: ags

DrawingSurface *mainBackground = Room.GetDrawingSurfaceForBackground(0);
DrawingSurface *nightBackground = Room.GetDrawingSurfaceForBackground(1);
DrawingSurface *copyBG = mainBackground.CreateCopy(); //is this a correct way to create the copy of the original surface?

int i = 90;
while ( i > 0 )
  {
    mainBackground.DrawSurface(nightBackground, i);
    // I'm not sure how to use the copyBG here and how to restore it :/
    copyBG.DrawSurface(mainBackground, 0);
    i --;
    Wait(1);
  }

mainBackground.Release();
nightBackground.Release();
copyBG.Release();

Game stats:
AGS version 3.3.3
Res 640x400 32 bit
Direct 3D 9 hardware acceleration

Thanks in advance 

Edit:

I managed to get a gradient effect with this:

Code: ags

DrawingSurface *mainBackground = Room.GetDrawingSurfaceForBackground(0);
DrawingSurface *nightBackground = Room.GetDrawingSurfaceForBackground(1);

int i = 90;
while ( i > 10 )
{
mainBackground = Room.GetDrawingSurfaceForBackground(0);
mainBackground.DrawSurface(nightBackground, i);
i --;
Wait(1);
mainBackground.Release();
}

nightBackground.Release();
mainBackground.Release();

[selmiak]

make the night BG a roomsized object and use the tween module to tween its transparency in, blocking or nonblocking. easy peasy and even with different curves for the tween.

[Snarky]

That won't work so well if the background includes e.g. walkbehinds, selmiak.

What you're doing is pretty obviously wrong. What you should do is grab a copy of each background as a surface or dynamicsprite at the beginning (personally I'd do this as soon as the room loads, because then you know that they haven't been messed with), and then never write to them: these are your sources, and they should not be affected by what you do. Then you get a drawingsurface for the background, and on each loop iteration you draw both the original drawingsurfaces/sprites to it (one at 100% first, and then the other at whatever % you're at), and release.

I wrote something like this a while back. There's a version of the code in last year's AGS Awards client.

[selmiak]

That won't work so well if the background includes e.g. walkbehinds, selmiak.

Alright, this is true, I didn't think of that, I always(!) use PNG objects instead of walkbehinds as walkbehinds are just awful to add and don't have semitransparency for the borders. Done the tweening way it works pretty well, I did it this way in Eternal Chrysalis and by now noone called me out on any crappy transitions.


(!) No, not really always, walkbehinds are good for doors and sideway exits and have their sparse reason to exist but I use overlapping PNG object as often as possible!

[Creamy]

Done the tweening way it works pretty well

That's what I did for A Sloth For Both Seasons too. It may not be conventional, but it works if you update the baseline of the background object in "repeatedly execute".