Pass 1 draws one raymarched gem on sheet 1 instead of plasma; its alpha
carries coverage rather than depth, so pass 2 can light it as a solid
while every other sheet still absorbs by path length.
Pass 1 renders eight plasma sheets into an atlas with linear depth in alpha;
pass 2 marches the refracted ray to each sheet and absorbs it by real path
length, so near and far layers separate under pointer parallax. Plasma cycle
repeats exactly every 30 s; - / = change speed.
emil28092005