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game/server/cstrike/cs_nav_generate.cpp

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+//========= Copyright Valve Corporation, All rights reserved. ============//
+//
+// Purpose: 
+//
+// $NoKeywords: $
+//
+//=============================================================================//
+// nav_generate.cpp
+// Auto-generate a Navigation Mesh by sampling the current map
+// Author: Michael S. Booth (mike@turtlerockstudios.com), 2003
+
+#include "cbase.h"
+#include "util_shared.h"
+#include "nav_mesh.h"
+#include "cs_nav_area.h"
+#include "cs_nav_node.h"
+#include "cs_nav_pathfind.h"
+#include "viewport_panel_names.h"
+
+enum { MAX_BLOCKED_AREAS = 256 };
+static unsigned int blockedID[ MAX_BLOCKED_AREAS ];
+static int blockedIDCount = 0;
+static float lastMsgTime = 0.0f;
+
+
+//ConVar nav_slope_limit( "nav_slope_limit", "0.7", FCVAR_GAMEDLL, "The ground unit normal's Z component must be greater than this for nav areas to be generated." );
+ConVar nav_restart_after_analysis( "nav_restart_after_analysis", "1", FCVAR_GAMEDLL, "When nav nav_restart_after_analysis finishes, restart the server.  Turning this off can cause crashes, but is useful for incremental generation." );
+
+
+//--------------------------------------------------------------------------------------------------------------
+/**
+ * Shortest path cost, paying attention to "blocked" areas
+ */
+class ApproachAreaCost
+{
+public:
+	// HPE_TODO[pmf]: check that these new parameters are okay to be ignored
+	float operator() ( CNavArea *area, CNavArea *fromArea, const CNavLadder *ladder, const CFuncElevator *elevator, float length )
+	{
+		// check if this area is "blocked"
+		for( int i=0; i<blockedIDCount; ++i )
+		{
+			if (area->GetID() == blockedID[i])
+			{
+				return -1.0f;
+			}
+		}
+
+		if (fromArea == NULL)
+		{
+			// first area in path, no cost
+			return 0.0f;
+		}
+		else
+		{
+			// compute distance traveled along path so far
+			float dist;
+
+			if (ladder)
+			{
+				dist = ladder->m_length;
+			}
+			else
+			{
+				dist = (area->GetCenter() - fromArea->GetCenter()).Length();
+			}
+
+			float cost = dist + fromArea->GetCostSoFar();
+
+			return cost;
+		}
+	}
+};
+
+/*
+ * Determine the set of "approach areas".
+ * An approach area is an area representing a place where players 
+ * move into/out of our local neighborhood of areas.
+ * @todo Optimize by search from eye outward and modifying pathfinder to treat all links as bi-directional
+ */
+void CCSNavArea::ComputeApproachAreas( void )
+{
+	m_approachCount = 0;
+
+	if (nav_quicksave.GetBool())
+		return;
+
+	// use the center of the nav area as the "view" point
+	Vector eye = m_center;
+	if (TheNavMesh->GetGroundHeight( eye, &eye.z ) == false)
+		return;
+
+	// approximate eye position
+	if (GetAttributes() & NAV_MESH_CROUCH)
+		eye.z += 0.9f * HalfHumanHeight;
+	else
+		eye.z += 0.9f * HumanHeight;
+
+	enum { MAX_PATH_LENGTH = 256 };
+	CNavArea *path[ MAX_PATH_LENGTH ];
+	ApproachAreaCost cost;
+
+	enum SearchType
+	{
+		FROM_EYE,		///< start search from our eyepoint outward to farArea
+		TO_EYE,			///< start search from farArea beack towards our eye
+		SEARCH_FINISHED
+	};
+
+	//
+	// In order to *completely* enumerate all of the approach areas, we
+	// need to search from our eyepoint outward, as well as from outwards
+	// towards our eyepoint
+	//
+	for( int searchType = FROM_EYE; searchType != SEARCH_FINISHED; ++searchType )
+	{
+		//
+		// In order to enumerate all of the approach areas, we need to
+		// run the algorithm many times, once for each "far away" area
+		// and keep the union of the approach area sets
+		//
+		int it;
+		for( it = 0; it < TheNavAreas.Count(); ++it )
+		{
+			CNavArea *farArea = TheNavAreas[ it ];
+
+			blockedIDCount = 0;
+
+			// skip the small areas
+			const float minSize = 200.0f;		// 150
+			Extent extent;
+			farArea->GetExtent(&extent);
+			if (extent.SizeX() < minSize || extent.SizeY() < minSize)
+			{
+				continue;
+			}
+
+			// if we can see 'farArea', try again - the whole point is to go "around the bend", so to speak
+			if (farArea->IsVisible( eye ))
+			{
+				continue;
+			}
+
+			//
+			// Keep building paths to farArea and blocking them off until we
+			// cant path there any more.
+			// As areas are blocked off, all exits will be enumerated.
+			//
+			while( m_approachCount < MAX_APPROACH_AREAS )
+			{
+				CNavArea *from, *to;
+
+				if (searchType == FROM_EYE)
+				{
+					// find another path *to* 'farArea'
+					// we must pathfind from us in order to pick up one-way paths OUT OF our area
+					from = this;
+					to = farArea;
+				}
+				else // TO_EYE
+				{
+					// find another path *from* 'farArea'
+					// we must pathfind to us in order to pick up one-way paths INTO our area
+					from = farArea;
+					to = this;
+				}
+
+				// build the actual path
+				if (NavAreaBuildPath( from, to, NULL, cost ) == false)
+				{
+					break;
+				}
+
+				// find number of areas on path
+				int count = 0;
+				CNavArea *area;
+				for( area = to; area; area = area->GetParent() )
+				{
+					++count;
+				}
+
+				if (count > MAX_PATH_LENGTH)
+				{
+					count = MAX_PATH_LENGTH;
+				}
+
+				// if the path is only two areas long, there can be no approach points
+				if (count <= 2)
+				{
+					break;
+				}
+
+				// build path starting from eye
+				int i = 0;
+
+				if (searchType == FROM_EYE)
+				{
+					for( area = to; i < count && area; area = area->GetParent() )
+					{
+						path[ count-i-1 ] = area;
+						++i;
+					}
+				}
+				else // TO_EYE
+				{
+					for( area = to; i < count && area; area = area->GetParent() )
+					{
+						path[ i++ ] = area;
+					}
+				}
+
+				// traverse path to find first area we cannot see (skip the first area)
+				for( i=1; i<count; ++i )
+				{
+					// if we see this area, continue on
+					if (path[i]->IsVisible( eye ))
+					{
+						continue;
+					}
+
+					// we can't see this area - mark this area as "blocked" and unusable by subsequent approach paths
+					if (blockedIDCount == MAX_BLOCKED_AREAS)
+					{
+						Msg( "Overflow computing approach areas for area #%d.\n", GetID());
+						return;
+					}
+
+					// if the area to be blocked is actually farArea, block the one just prior
+					// (blocking farArea will cause all subsequent pathfinds to fail)
+					int block = (path[i] == farArea) ? i-1 : i;
+
+					// dont block the start area, or all subsequence pathfinds will fail
+					if (block == 0)
+					{
+						continue;
+					}
+
+					blockedID[ blockedIDCount++ ] = path[ block ]->GetID();
+
+					// store new approach area if not already in set
+					int a;
+					for( a=0; a<m_approachCount; ++a )
+					{
+						if (m_approach[a].here.area == path[block-1])
+						{
+							break;
+						}
+					}
+
+					if (a == m_approachCount)
+					{
+						m_approach[ m_approachCount ].prev.area = (block >= 2) ? path[block-2] : NULL;
+
+						m_approach[ m_approachCount ].here.area = path[block-1];
+						m_approach[ m_approachCount ].prevToHereHow = path[block-1]->GetParentHow();
+
+						m_approach[ m_approachCount ].next.area = path[block];
+						m_approach[ m_approachCount ].hereToNextHow = path[block]->GetParentHow();
+
+						++m_approachCount;
+					}
+
+					// we are done with this path
+					break;
+				}
+			}
+		}
+	}
+}