How “oldschool” graphics work, part 2 – Apple and Atari

Therefore welcomed segment 2 of “How Old School Graphics Work”. Now, in the last episode, I plastered some of the more popular methods in the eighties, like the Nintendo and the Commodore organisations, and in this episode I’m going to cover the Apple II and some other structures. Now, the Apple II is one of the more complicated and difficult to explain graphics of all, and to be honest it actually works like two completely different computers depending upon whether you have a monochrome monitor or emblazon observer is connected to it make this example this is a zoomed in view of what the pixels would look like on each type.Now, to better understand why it wreaks this route let’s break it down a bit further. The screen is divided up into divisions of 7 pixels each. So, let’s see what goes on inside these slice. Eight bits of retention are used to define the 7 pixels. The leftover bit is used to change the palette. So, here’s how the present working: on a monochrome monitor, if you turn on some fragments in retention like this, the corresponding pixels will turn on, and you’ll get the result you pretty much expected. So, what happens when we toggle this part on and off? Pretty much nothing. So, on a monochrome screen, the Apple II had a particularly crisp graphics expose and was generally enormous for business applications. OK , now let’s computed a complexion observer for purposes of comparison. One of the first things you might notice when looking at an Apple II on a hue observer is that the text often ogles rainbow-colored. Now, there’s actually a reason for this and it has to do with the channel the machine produces color. So, let’s go back to our pixel diagram.If you turn on some chips you’ll to be provided with dyes, and you deepen the dye by moving the orientation of the pixel like this. If you move the pixel to one side, you get green, and on the other side you get violet. Now, if you set two pixels next to each other you get lily-white. So, that gives you four possible complexions. But remember this control bit here? Watch what happens when we turn it on now. Notice the emblazons change to orange and off-color. So, that additional dominate bit allows you to use two added dyes. But keep in mind that you can’t use these complexions in the same 7-bit section as these colors, so it’s very difficult to have blue-blooded and lettuce next to each other on the screen, unless you line it up just perfectly. And now you can see why textbook would look rainbow-colored when using a emblazon observe. Now, we’ve been talking about high-pitched solution state, which almost every games were designed for, but Apple also gave us a low-grade solution mode with 40 by 48 pixels.The pixels are huge and chunky, but you do get a total of 16 dyes, hence why the Apple II claims to be a 16 -color computer. Now, later on, when Apple introduced the Apple IIc and Apple IIe computers, they did add the capabilities needed for more colorings in high-pitched solving procedure, but it was rarely consumed because game developers wanted to maintain compatibility with older Apples. All privilege. So if you pointed out that disorient, don’t feel bad. There are very few people that really comprehend how Apple II graphics drive. And also I want to defend the computer a little bit for those who might say, “Wow! It can only do six dyes when in high settlement graphics mode for plays and material. That’s terrible! ” But you kind of have to keep it in perspective that this machine came out in 1977, which was a good five years earlier than arrangements like the Nintendo and the Commodore.So, OK, there’s one more type of graphics plan I want to talk about. It’s called CPU-driven graphics, and let me show you how this works. I caused some oversized pixels on this illustration. First of all, you have to keep in mind that the pixels are drawn on the screen one at a time starting on the top-left, moving to the right, and then dropping down. Of trend, all this happens in the blink of an eye. In fact, that happens 30 durations two seconds. Most computers have a dedicated video chipping that casts pulsings to the monitor, in the correct succession and era, to draw the picture on the screen. However, some plans had no video chip at all, and use the CPU to drive the pulsates directly.OK, so this does actually succeed, but it requires an enormous amount of the CPU’s time in order to attract this off. So, that left very little CPU time left over to run game code. Imagine if they did this on a modern arrangement, and you opened your exercise overseer, and there was always a project guiding announced “Video Generator”, and it took up ninety percentage of your computer’s CPU time. What a drag well, huh? Games designed for the Atari 2600 were quite a challenge because of this. In fact, if you ever noticed in some plays, if you look over to the left side of the screen and assure these inexplicable blacknes ways, those are there because game code is running and there’s just not enough time to draw the screen and guide the game code at the same time.Now, one last thing I’m going to mention is it is actually possible to use a little bit of CPU-driven graphics even on a machine that has a traditional graphics microchip. You know those colour cadres we talked about in the last episode? Well, if a programmer wanted, he could use the CPU to change the color palette on each scanline. This allowed some pretty incredible artwork on the Commodore 64, but this was never used in tournaments because it pretty much chewed up all of the available CPU time. All claim, so that about wrappings it up for this episode. In the next escapade, I’m going to be encompas how old school sound and music worked, and if there’s enough interest I might actually make one on IBM, CGA, EGA, and VGA graphics modes.Don’t forgotten to like my video and agree, and too check out my Facebook page–there’s a relation down at the bottom. I’ll see you next time !.

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