Tianjun Wang

This week I made an electronic candle using programmable LED together with Zan. First, we abstract several behaviors and principles of candle light:

• Candle light is composed of several layers, and different layers have different features on its color and lightness. The inner layer of the candle light is pale yellow, quite stable and bright. And the outer layer gets warmer with more red color, less stable swinging around and looks weaker. The very bottom of the candle fire gives off pale blue light, with very high temperature. We only choose to stimulate the upper two layers in this 2D electronic candle version. The word “stable” used above is to describe the shape and movement of the light layers. And lightness, color features would be described by Lightness and Hue/Saturation value in HSL model.

• The candle light is always swinging around and blinking, especially for its outer layer. The programmable LED toolkit has seven LEDs, six LEDs surrounding one. So we divided the outer layers six LEDs into three groups and let the brightest part looping among them. For this each of group is assigned with a specific phase in sinFade function which controls lightness of each group. And the phase difference produces the swing effect. The reason for choose sinFade is the candle light behaves more smoothly when it nearly climbing to the top and falling to the ground, not like the bumping fire liking opening a new champagne. First we tried the phase difference is PI/3. However, maybe because the diffuser is too strong, the total lightness too stable and the swinging effect is weak. So we combine the two parts of the three and change the phase difference to PI/6, so there would be a clear swinging and breathing effect. For the inner layer,  the centered LED always remain pale yellow and the same lightness when the outer layers swinging around.

• The color of the fire fire depends on its temperature. The fire with higher temperature is always more stable, so it looks more strong. So we choose to calculate the hue value from the lightness value in HSL system. We do mapping from the L domain to the H domain and define each hue value by the lightness value in negative correlation. Hue value= 15-(Lightness value-40)/10.

Then we began prototyping the diffuser. Inspired by my last week’s observation, first I tried to use glass and water to generate specific light pattern. The effect is quite intriguing.

Then we tried prototyping different diffuse: Writing paper, Coffee filter paper, Water& Glasses and two-side Plastic Roll.

In the end, we chose onion skins, a fire-shape diffuser with an organic pattern. It also helps to render 3D effects and color gradients from bottom to top in candlelight.

If I have more time I would try to add more randomness into its behavior. Now it is showing too obvious periodicity.