seascape snippet

gistfile1.txt

// from "Seascape" by Alexander Alekseev aka TDM - 2014
// License Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

float heightMapTracing(vec3 ori, vec3 dir, out vec3 p) { ```
    float tm = 0.0;
    float tx = 1000.0;    
    float hx = map(ori + dir * tx);
    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;
}

gistfile2.txt

(defn height-map-tracing [ori ; vec3
                          dir ; vec3
                          p ; vec3 <- "OUT"
                          {:keys [num-steps]
                           :as opts}]
  (if (> hx 0)
    tx
    (loop [i 0,
           p p,
           ;; using a vector so we only need 1 g/if. benchmarks would be nice.
           tx-hx-tm-hm (g/vec4
                         ;; maybe unity profiler supports this?
                         1000
                         (sea-map (g/+ ori dir tx) opts)
                         0
                         (sea-map (g/+ ori (g/* dir tm))))]
      (let [[tx hx tm hm] (gvdest tx-hx-tm-hm)]
        (if (< i num-steps)
          (let [tmid (mix tm, tx, (g/div hm (g/- hm hx)))
                p2 (g/+ ori (g/* dir tmid))
                hmid (sea-map p opts)]
            (recur
              (inc i),
              p2,
              (g/if (g/< hmid 0)
                (g/vec4 tmid hmid tm hm)
                (g/vec4 tx hx tmid hmid))))
          {:p p, :tmid tmid})))))