AMOS - Double Buffering

[ricky500]

I'm working on my first AMOS program -so sorry if I sound like a newbie!

I have some BOBs that I need animated without flicker so I am using the DOUBLE BUFFER command to turn on double buffering.

Once I turn on double buffering, I found that CLS does not clear the screen. I played around with the AUTOBACK command, but wasn't able to find a solution. I found a work around - I call a CLS then SWITCH SCREEN and then another CLS - SWITCH SCREEN and CLS again. (With some WAITs in-between) Is this the best method?

Also is there a way to turn off double buffering once you turned it on?

[volvo_0ne]

1) CLS 0
Strangely enough I never encountered this problem until I tested today, but I suppose it's good practice to specify the colour to CLS to, just incase the PAPER colour has been changed during your program run.

and

2) BOB UPDATE OFF/ON
Should start/stop the DB process for you.

[ricky500]

Originally Posted by volvo_0ne

1) CLS 0
Strangely enough I never encountered this problem until I tested today, but I suppose it's good practice to specify the colour to CLS to, just incase the PAPER colour has been changed during your program run.

I tried CLS with the 0 and it worked! Must be a weird glitch, since according to the manual, CLS by itself is supposed to fill with colour 0 by default.

2) BOB UPDATE OFF/ON
Should start/stop the DB process for you.

Yes, that worked! Thanks!!

[volvo_0ne]

Originally Posted by ricky500

I tried CLS with the 0 and it worked! Must be a weird glitch, since according to the manual, CLS by itself is supposed to fill with colour 0 by default.



Yes, that worked! Thanks!!

Don't forget that the "0" could be any colour of your palette (sometimes handy for effects)

[Dan]

Also is there a way to turn off double buffering once you turned it on?

I guess Double buffer turns off when you close and open the screen again.

[idrougge]

Doesn't the Autoback command control that?

[Dan]

No.

As far as i know, amos pro does not automatically make a double buffered screen.
As this would take up more memory and slow everything down.

You need to use "Double Buffer" command, to create an invisible buffer copy of the screen.

But to turn off this system, then the screen has to be closed and to be reopened.

Originally Posted by http://www.ultimateamiga.co.uk/HostedProjects/AMOSFactory/AMOSProManual/index.html

DOUBLE BUFFER
instruction: activate Double Buffering system
Double Buffer

Throughout this Chapter, extensive reference is made to the technique known as "double buffering". The DOUBLE BUFFER command creates an invisible copy of the current screen and stores it as a "logical screen". All graphics operations, including Bob movements, are now performed directly on this logical screen, without disturbing your existing display at all. This is because the existing display on your television screen is taken straight from the original screen area, now called the "physical screen".

Once the image has been re-drawn, the logical screen and physical screen are swapped over. The old logical screen is flicked onto the display, and the old physical screen is hidden away to become the new logical screen. The entire process now cycles continuously, producing a solid, smooth display, even when dozens of Bobs are moving on the same screen.

Autoback modes then sets how the things are drawn on physical screen and on the buffered copy:

There are three AUTOBACK modes, and you can toggle between them by setting the mode values as follows:

X> Autoback 0
Manual mode. This mode deactivates the AUTOBACK system completely, so that graphics are drawn directly on the logical screen, for maximum speed. It is recommended for use with the BOB DRAW and BOB CLEAR commands.

AUTOBACK 0 is useful when large amounts of graphics are drawn on screens being switched manually with SCREEN SWAP, because it is much faster than the standard system. But remember that you must take responsibility for synchronising between the logical and physical screens.

X> Autoback 1
Semi-automatic. In mode 1, AUTOBACK performs all graphical operations on both the logical and physical screens. Although Bob updates are not taken into account, this is an ideal mode for displaying hi-score tables and control panels. So as long as your Bobs are kept clear of any new graphics, this mode is perfect.

X> Autoback 2

here are few links to the amos pro manual which explains this a bit better:

AutoBack

Double Buffering

Blitter Objects

and the last one, but important for bobs on Single buffered screen:

Updating objects


It sounds a bit complicated, but only practice and the examples can show you how it is done.