I was going over my archives, and stumbled on a couple of video games I was working on around 2002. There were two visual effects that I liked in particular, and the genesis of each of them had an interesting element of chance, so I thought I would bring them back. The original code was written in a mixture of C and assembly on Windows 95, so it took a little porting, but the concepts in computer graphics haven't changed all that much in the past decade, so the port wasn't that complicated.

Dice

I used this effect in an implementation of the game Risk. I wanted to illustrate a roll of dice. The whole game had a kind of ephemeral feel to it, and I wanted the dice to feel that way too. At first, I wanted to cycle through random faces, which would fade out before a new face appeared, but I accidentally committed an off-by-one error, which made the effect look much better.

The way I faded the dice was to cycle through each pixel of the display, read the color value of each pixel, fade the color a little (by making it get a little closer to black – in the original version of the game – or white in this port) and then draw the pixel back on the display, this time with the right color. By mistake, I drew the color one pixel higher than I should have. As a result, the dice not only faded, but also shifted up, which made them look like they were evaporating:

Fire

Another time I wanted to simulate fire in a platform game that I was designing. The fire would come from a torch attached to a cave. The torch was pretty small, but I wanted the fire to look elaborate. And so, I wanted to model three aspects of it:

The flame, which has a generally upward shape, broad at the bottom and narrowing towards the top, and which follows a color spectrum consistent with fire (from red to yellow)
Sparks, which are visible separately from the flame, also changing in color as they move away from the fire source
The fact that the fire make the surrounding portion of the cave brighter

I decided to simulate the motion of 80 light particles, which had a position and a temperature (which defined their color and presence – if a particular got too cool, it would disappear and a new one would appear at the source of the light). In addition to this, I would lighten the cave within a particular radius of the center of the light source. It took me a while to create the flame, but then, quite by chance, I decided to blur each light particle, and realized that doing that pretty much created the flame for me. Come to think about it, it makes sense – the complete flame is just an averaging of the individual light particles.

References

To see the dice effect on a new page, click here.
To see the fire effect on a new page, click here.
The source code for the dice and fire effect can be found in this repository.