Ice slab with layered plasma, two-pass refraction

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.

2_tunnel.frag

@@ -0,0 +1,17 @@
+precision highp float;
+uniform vec2 u_res; uniform float u_time; uniform vec2 u_mouse;
+void main(){
+ vec2 p=(gl_FragCoord.xy-0.5*u_res)/u_res.y;
+ float t=u_time*0.6;
+ float a=atan(p.y,p.x);
+ float r=length(p)+0.001;
+ float z=1.0/r+t;
+ float rings=fract(z*2.0+a*0.6+sin(a*3.0+t)*0.3);
+ vec3 base=mix(vec3(1.0,0.15,0.55),vec3(0.15,0.9,1.0),smoothstep(0.0,1.0,rings));
+ float glow=pow(1.0-r,2.0);
+ float band=smoothstep(0.45,0.5,rings)*smoothstep(0.6,0.5,rings);
+ vec3 col=base*band*glow*2.2;
+ col+=vec3(0.9,0.5,1.0)*pow(glow,8.0)*1.5;
+ col+=0.02*vec3(0.3,0.1,0.5)/(r*r);
+ gl_FragColor=vec4(col,1.0);
+}