In the last episode we learned how to code the rotozoom effect using floating point arithmetics. This however is pretty slow on ancient DOS machines, like 486 and even worse on slower machines. So in this episode we will rewrite the program to use integer based fixed point arithmetics.
One ubiquitous demo effect that can be seen on a wide variety of demos and intros is the twister or the twister bar. There are numerous examples in productions for the Amiga, Atari ST and 2600 that I know of (and even at least one on the Sega Master System). And probably a lot more that I don’t know. However I have never seen this effect in any of the old PC demos, except maybe in Future Crew’s PANIC, where something very similar was used for the vertical scrolling greetings. But it was not quite the same still. So today we will code a variant of the twister using Turbo C for MS DOS!
It’s summer and it’s hot. And what better to code than another classic demo scene effect: the ubiquitous fire. But we will do it with a twist. The naive implementation is slow, very slow. Especially on older 286-486 computers. We will optimize the actual algorithm a bit and utilize a hidden VGA function that gives us scaling in the X-direction by a factor of 4 for free.
I am a big fan of interactive fiction, better known as text adventures. I am also a big fan of MS DOS games. And retro games in general. And when there is a new release of a retro game, a text adventure, which supports MS DOS and other platforms, I am all ears. Enter: The Curse of Rabenstein. A brand new release with a nice physical big box with lots of goodies. But is the game also a goodie? Let’s see…
I got a question in the YouTube comments about the sine tables that we used for a few animations, like the Copper Bars, the Smooth Scrolling etc. In this episode I try to explain why and how to create sine tables. The idea is to speed up computations, since computing the sine or cosine — even with an FPU — takes an awfully long time on early MS DOS machines.
In the last live stream we did some Turbo C inline assembly, which was pretty fun. But let’s today use an actual pure assembler: the Borland Turbo Assembler. And let’s demystify some of the things surrounding assembly language. It is actually not that hard, so let’s write a hello world program, using assembly, for MS DOS!
Today we continue on our quest to make a small VGA game. So far we learned how to initialize Mode X and use some of its nice features. Copying images from system memory was painfully slow though. So let’s make it faster with a small trick!
The next part in the series about VGA Mode X programming. Let’s do some smooth scrolling. We already did that in text mode, but not in graphics mode, and not in a horizontal direction. So let’s lay down some basics!
Today we’ll tackle a more complicated topic. That’s also why the video is rather long with 40 Minutes. However I think this is necessary, given the importance of the topic. The VGA card is surprisingly feature rich. However a lot of these features are not accessible from the standard 256 color mode 13h. That’s why we take a look at Mode X today, which unlocks such features as page flipping, scrolling and giving access to the VGA’s full memory.