AbeDemoschool

Welcome to part V of Abe's Demoschool. In Part 4 I said that this part would be about 3d vector graphics but I've changed my mind because I'm taking a course about 3d computer graphics in the spring of 1997 and I thought it would be best to wait with the 3d stuff until after that course so I'll be sure I'm not telling any lies. Instead I'm going to write about some easier common demoeffects and I'll start with the lens effect and similar transformations . A lens effect is when a picture is shown and it looks like a magnifying glass is beeing drawn over the picture. One of the most famous demos that has a lens e...

Now it's finally time to enter the dark, mysterious world of 3d graphic programming. There are enormous amounts of information available on this subject. I've gone through many files and some books on 3d demo and game programming and in this part I'm going to present the basic math and algorithms that 3d computer graphics are built upon. 3d graphics is simply an extension of 2d graphics. Because of that I'll begin with 2d-graphics. In 2d, a point is represented by an X and a Y -coordinate, written (X,Y). Origo is the point where both the X and Y coordinate is 0, (0,0). For simplicity, imagine origo being the middle of the ...

Hello and welcome to part 3 of Abe's Demoschool. Last part was pretty messy so this time I'll show you how to split a demo up into several files and link them all together into one executable file. In this part we'll also cover sprite's and how to show a TGA picture to the screen. I think it's enough with the TGA format since most drawing programs can convert pictures into the TGA format. The TGA format is also one of the most simple formats. WHAT IS A SPRITE? A sprite is a rectangular 2-dimensional picture made up of pixels that can be drawn on different positions on the screen. Games often use sprites. In a pinball g...

Today I'll cover how to fade the palette in and out, how to display text in graphic mode, how to use precalculated lists and how to use a virtual screen. I told you how to set the palette in part 1 of the demoschool, to fade the palette is similar to setting the palette repeaditly with slightly different values. A common trick is to set all the colors of the palette to black, then draw something to the screen and finally fade the palette in. That way the whole picture will fade in simultaneously no matter how much is on the screen. Like you remember, the palette is set through ports 3c8h and 3c9h. The index of the color that shall be ...

Welcome to part I of the Demoschool. In the demoschool I'll guide you through different demoeffects such as paletterotation, plasma, fire, sprites, 3d- vector-graphics, shading, warping, mode-X, Soundblaster and whatever else that might show up. Most parts of the demoschool will be in mode 13h or MCGA-mode as it is also called. That immediately brings up the first question: What is mode 13h? Well, the answer is easy, mode 13h is the graphic mode of the PC that most games and demos are written for. The resolution of mode 13h is 320 pixels horizontally and 200 pixels vertically. that makes 320*200 = 64000 pixels totally on the screen. T...