htdocs: live 3D view of a run coupled to Meso-NH

CHANGELOG.md

@@ -14,6 +14,8 @@ history, so they summarise each release rather than list every change. The
 
 ### Added
 
+- `tools/htdocs/mnh3d.html` shows a run coupled to Meso-NH live in 3D:
+  terrain, fuel, fire front, plume top and surface wind.
 - The browser demo can draw the DFCI grid, water points and DFCI tracks from
   the IGN Géoplateforme, in France. These layers are display only: they never
   reach the simulation.

docs/mnh/coupledMNHInstall.md

@@ -87,6 +87,13 @@ on 6.1). A meaningful check is the comparison in section 5.
 `mnh_real_nested/ForeFire/Init.ff` starts
 `listenHTTP[host=127.0.0.1:8080]`, so port 8080 must be free.
 
+To watch the run in 3D (terrain, fire front, plume, wind), export
+`FOREFIREHOME=/path/to/forefire` before `run.bash` and open
+<http://localhost:8080/mnh3d.html> while it runs (it loads three.js from a
+CDN, so the browser needs internet). The page sends commands that run
+alongside the time step, so leave it closed for the comparison in section 5;
+use one tab at a time.
+
 ## 5. Check that a change does not alter coupled results
 
 Run the same case with ForeFire built from `dev` and from the branch under