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Multiple graphic screens? RRS feed

  • Question

  • In Applesoft Basic there was a HGR and HGR2 commands that would show a High resolution GRaphics screen and a seperate, 2nd, High resolution GRaphics screen.
    So I could draw somthing on the first screen, throw it up and, while watching that screen, draw something on the second screen and then throw HGR2 up - that way the user doesn't see the screen drawing.

    Does Small Basic, or will it, have something like that?
    Wednesday, December 17, 2008 7:41 PM

Answers

  • Hi DRC,

    Back in the day, where direct access to video memory was provided, we had the issue of screen flicker when you erased a particular portion of the screen and redrew it in order to give it the motion effect.  Hence we devised this technique of rendering in the background and switching the Video memory pointer to eliminate the flicker.  This was called double-buffering.  Of course such techniques were then employed to perform various other effects.

    In these modern times, the presentation layer that Small Basic uses (WPF) takes care of all those gory details for us and provides us with a retained graphics facility.  There is no need to deal with flicker as such. 

    If you can describe what you're trying to do, we may be able to help out with a different strategy.

    Friday, December 19, 2008 2:38 AM
    Moderator

All replies

  • Hi DRC,

    Back in the day, where direct access to video memory was provided, we had the issue of screen flicker when you erased a particular portion of the screen and redrew it in order to give it the motion effect.  Hence we devised this technique of rendering in the background and switching the Video memory pointer to eliminate the flicker.  This was called double-buffering.  Of course such techniques were then employed to perform various other effects.

    In these modern times, the presentation layer that Small Basic uses (WPF) takes care of all those gory details for us and provides us with a retained graphics facility.  There is no need to deal with flicker as such. 

    If you can describe what you're trying to do, we may be able to help out with a different strategy.

    Friday, December 19, 2008 2:38 AM
    Moderator
  • Well, I was toying with an idea of drawing the walls to my 3D maze from farthest to closest and as the closer walls draw, they will cover the farther walls.
    So I didn't want the user to see all the walls being drawn.

    It's a lazy approach to getting the proper view/perspective, so not a big deal.
    I'll just handle it by using more If-Thens to figure out not to draw a wall when there is a wall blocking the view.
    Monday, December 22, 2008 3:14 PM