elevmgr: added clbkFilterElevation

Clients that manipulate elevation file data in memory (e.g. for
flattening features) for visuals can overload this method in order to
manipulate the terrain collision data in the same way. As soon as the
internal collision tile is loaded in the core, the callback is invoked.

Orbitersdk/include/GraphicsAPI.h

@@ -1353,6 +1353,23 @@ class OAPIFUNC GraphicsClient: public Module {
 	bool ElevationGrid (ELEVHANDLE emgr, int ilat, int ilng, int lvl,
 		int pilat, int pilng, int plvl, INT16 *pelev, INT16 *elev, double *emean=0) const;
 
+	/**
+	 * \brief Filter elevation grid data
+	 * \param hPlanet object handle of the planet the data belongs to
+	 * \param ilat patch latitude index
+	 * \param ilng patch longitude index
+	 * \param lvl patch resolution level
+	 * \param elev_res elevation level resolution
+	 * \param elev pointer to array with elevation grid data
+	 * \default None.
+	 * \note Clients that manipulate elevation file data in memory (e.g. for flattening
+	 *   features) for visuals should overload this method in order to manipulate the
+	 *   terrain collision data in the same way. As soon as the internal collision tile
+	 *   is loaded in the core, the callback is invoked.
+	 */
+	virtual bool clbkFilterElevation(OBJHANDLE hPlanet, int ilat, int ilng, int lvl, double elev_res, INT16* elev) { return false; }
+	// @}
+
 protected:
 	/** \brief Launchpad video tab indicator
 	 *

Src/Orbiter/elevmgr.cpp

@@ -311,6 +311,8 @@ double ElevationManager::Elevation (double lat, double lng, int reqlvl, std::vec
 					t->lngmin = (double)ilng/(double)nlng*Pi2 - Pi;
 					t->lngmax = (double)(ilng+1)/(double)nlng*Pi2 - Pi;
 					// still need to store emin and emax
+					auto gc = g_pOrbiter->GetGraphicsClient();
+					if (gc) gc->clbkFilterElevation((OBJHANDLE)cbody, ilat, ilng, lvl, elev_res, t->data);
 					break;
 				}
 			}