Plasma Effect

A plasma effect is a classic of demoscene graphics: a few sines and cosines of the pixel position, mixed together and pushed through a color ramp, produce a slowly flowing pattern that never repeats exactly. This one is a port of a Shadertoy fragment shader (4tdGWX). Each point of the plane is first shifted by the time T, so the whole picture drifts diagonally. From the shifted point the document builds two phases, k from the vertical coordinate and w from the horizontal one, both of which also advance with T at their own rates, and the distance d to the origin. The field s = 7\cos(d + w)\sin(k + w) multiplies a radial wave by a wave in k, so the rings around the origin are modulated by horizontal bands.

The shader colors each pixel with the cosine palette 0.5 + 0.5\cos(s + (0.2, 0.5, 0.9)), one channel per number. The three channels are nearly in phase, so the palette reads as a brightness ramp from a deep blue-black to a warm cream. The heatmap keeps that ramp: it plots 0.5 + 0.5\cos(s + 0.5) on [0, 1] through a dark-to-light palette. Because s spans about two full periods of the cosine, each ring appears twice as a bright and a dark band. The time T animates at one unit per second, as in the original.