There seem to be an uninitialized out variable in one of the shaders (s01-ps.frag).
It causes ugly black rectangles on sky on Intel graphics.
Part of the shader with proposed change:
float heightMapTracing(vec3 ori, vec3 dir, out vec3 p) {
float tm = 0.0;
float tx = 1000.0;
float hx = map(ori + dir * tx);
p = vec3(0.0f, 0.0f, 0.0f); // <= proposed change
if(hx > 0.0) return tx;
float hm = map(ori + dir * tm);
float tmid = 0.0;
for(int i = 0; i < NUM_STEPS; i++) {
tmid = mix(tm,tx, hm/(hm-hx));
p = ori + dir * tmid;
float hmid = map(p);
if(hmid < 0.0) {
tx = tmid;
hx = hmid;
} else {
tm = tmid;
hm = hmid;
}
}
return tmid;
}