Re: Apple II VGA Video Generator Card Project

[bieling@terra.es]

Michael J. Mahon ha escrito:

> Jorge Chamorro Bieling wrote:
> > Michael J. Mahon <mjmahon@aol.com> wrote:
> >
> >
> >>While the time to put a character in a buffer is constant regardless
> >>of the frame buffer size, drawing a line is proportional to the size
> >>of the frame buffer, so all line drawing will take longer.
> >
> >
> > You mean
> > 1. drawing a longer line takes longer
> > or
> > 2. drawing the same lenght line takes longer
>
> I mean that a line that is half the width of the screen takes
> longer, because it has 1) more pixels, and 2) each pixel has
> more bits.
>
> If we are looking at vectors, then the time for a constant speed
> processor to draw them goes up as the square root of the frame
> buffer size.  (Of course, the time to fill an area goes up
> directly with frame buffer size.)

Yes, at "constant speed" for any given depth

1.- It takes n times longer to draw n*x pixels as it takes to draw x
pixels. (lines)
2.- It takes n*n times longer to draw of n*x*n*x pixels as it takes to
draw x*x pixels. (areas)

But "takes longer" is not a measure of drawing speed.
The space, measured in pixels, is missing in this equation :
(drawing speed) = (pixels drawn) / (time to draw them).

And the frame buffer size is not, nor direct nor indirectly, in this
equation.

So a drawing only "takes longer"

    1.- When you are drawing more pixels (so obvious!).
    2.- For frame buffers whose *depth* is bigger not whose *size* is
bigger.

The VGA card DOES NOT slow drawing speed at all... :-)