Misc/abrash-black-book
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James Gregory 2013-12-30 18:34:31 +11:00
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49-05.md
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@ -2,16 +2,16 @@
[Previous](49-04.html) [Table of Contents](index.html) [Next](50-01.html)
------------------------ --------------------------------- --------------------
Here’s something worth noting: The animation is extremely smooth on a 20
Here's something worth noting: The animation is extremely smooth on a 20
MHz 386. It is somewhat more jerky on an 8 MHz 286, because only 30
frames a second can be processed. If animation looks jerky on your PC,
try reducing the number of kites.
The kites draw perfectly into the background, with no interference or
fringe, thanks to masked copying. In fact, the kites also cross with no
interference (the last-drawn kite is always in front), although that’s
interference (the last-drawn kite is always in front), although that's
not readily apparent because they all look the same anyway and are
moving fast. Listing 49.5 isn’t inherently limited to kites; create your
moving fast. Listing 49.5 isn't inherently limited to kites; create your
own images and initialize the object list to display a mix of those
images and see the full power of Mode X animation.
@ -37,7 +37,7 @@ chapters.
.code
public _ShowPage
_ShowPage proc near
push bp ;preserve caller’s stack frame
push bp ;preserve caller's stack frame
mov bp,sp ;point to local stack frame
; Wait for display enable to be active (status is active low), to be
; sure both halves of the start address will take in the same frame.
@ -63,27 +63,27 @@ chapters.
in al,dx
test al,08h
jz WaitVS ;vertical sync is active high (1 = active)
pop bp ;restore caller’s stack frame
pop bp ;restore caller's stack frame
ret
_ShowPage endp
end
### Works Fast, Looks Great {#Heading8}
We now end our exploration of Mode X, although we’ll use it again
We now end our exploration of Mode X, although we'll use it again
shortly for 3-D animation. Mode X admittedly has its complexities;
that’s why I’ve provided a broad and flexible primitive set. Still, so
that's why I've provided a broad and flexible primitive set. Still, so
what if it *is* complex? Take a look at Listing 49.5 in action. That
sort of colorful, high-performance animation is worth jumping through a
few hoops for; drawing 20, or even 10, fair-sized objects at a rate of
60 Hz, with no flicker, interference, or fringe, is no mean
accomplishment, even on a 386.
There’s much more we could do with animation in general and with Mode X
in particular, but it’s time to move on to new challenges. In closing,
I’d like to point out that all of the VGA’s hardware features, including
There's much more we could do with animation in general and with Mode X
in particular, but it's time to move on to new challenges. In closing,
I'd like to point out that all of the VGA's hardware features, including
the built-in AND, OR, and XOR functions, are available in Mode X, just
as they are in the standard VGA modes. If you understand the VGA’s
as they are in the standard VGA modes. If you understand the VGA's
hardware in mode 12H, try applying that knowledge to Mode X; you might
be surprised at what you find you can do.