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game/server/NextBot/Path/NextBotChasePath.cpp

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+//========= Copyright Valve Corporation, All rights reserved. ============//
+//
+// Purpose:
+//
+//=============================================================================
+
+#include "cbase.h"
+
+#include "NextBotChasePath.h"
+#include "tier1/fmtstr.h"
+
+// memdbgon must be the last include file in a .cpp file!!!
+#include "tier0/memdbgon.h"
+
+
+//----------------------------------------------------------------------------------------------
+/**
+ * Try to cutoff our chase subject
+ */
+Vector ChasePath::PredictSubjectPosition( INextBot *bot, CBaseEntity *subject ) const
+{
+	ILocomotion *mover = bot->GetLocomotionInterface();
+
+	const Vector &subjectPos = subject->GetAbsOrigin();
+
+	Vector to = subjectPos - bot->GetPosition();
+	to.z = 0.0f;
+	float flRangeSq = to.LengthSqr();
+
+	// don't lead if subject is very far away
+	float flLeadRadiusSq = GetLeadRadius();
+	flLeadRadiusSq *= flLeadRadiusSq;
+	if ( flRangeSq > flLeadRadiusSq )
+		return subjectPos;
+
+	// Normalize in place
+	float range = sqrt( flRangeSq );
+	to /= ( range + 0.0001f );	// avoid divide by zero
+
+	// estimate time to reach subject, assuming maximum speed
+	float leadTime = 0.5f + ( range / ( mover->GetRunSpeed() + 0.0001f ) );
+	
+	// estimate amount to lead the subject	
+	Vector lead = leadTime * subject->GetAbsVelocity();
+	lead.z = 0.0f;
+
+	if ( DotProduct( to, lead ) < 0.0f )
+	{
+		// the subject is moving towards us - only pay attention 
+		// to his perpendicular velocity for leading
+		Vector2D to2D = to.AsVector2D();
+		to2D.NormalizeInPlace();
+
+		Vector2D perp( -to2D.y, to2D.x );
+
+		float enemyGroundSpeed = lead.x * perp.x + lead.y * perp.y;
+
+		lead.x = enemyGroundSpeed * perp.x;
+		lead.y = enemyGroundSpeed * perp.y;
+	}
+
+	// compute our desired destination
+	Vector pathTarget = subjectPos + lead;
+
+	// validate this destination
+
+	// don't lead through walls
+	if ( lead.LengthSqr() > 36.0f )
+	{
+		float fraction;
+		if ( !mover->IsPotentiallyTraversable( subjectPos, pathTarget, ILocomotion::IMMEDIATELY, &fraction ) )
+		{
+			// tried to lead through an unwalkable area - clip to walkable space
+			pathTarget = subjectPos + fraction * ( pathTarget - subjectPos );
+		}
+	}
+
+	// don't lead over cliffs
+	CNavArea *leadArea = NULL;
+
+#ifdef NEED_GPGLOBALS_SERVERCOUNT_TO_DO_THIS
+	CBaseCombatCharacter *pBCC = subject->MyCombatCharacterPointer();
+	if ( pBCC && CloseEnough( pathTarget, subjectPos, 3.0 ) )
+	{
+		pathTarget = subjectPos;
+		leadArea = pBCC->GetLastKnownArea(); // can return null?
+	}
+	else
+	{
+		struct CacheEntry_t
+		{
+			CacheEntry_t() : pArea(NULL) {}
+			Vector target;
+			CNavArea *pArea;
+		};
+
+		static int iServer;
+		static CacheEntry_t cache[4];
+		static int iNext;
+		int i;
+
+		bool bFound = false;
+		if ( iServer != gpGlobals->serverCount )
+		{
+			for ( i = 0; i < ARRAYSIZE(cache); i++ )
+			{
+				cache[i].pArea = NULL;
+			}
+			iServer = gpGlobals->serverCount;
+		}
+		else
+		{
+			for ( i = 0; i < ARRAYSIZE(cache); i++ )
+			{
+				if ( cache[i].pArea && CloseEnough( cache[i].target, pathTarget, 2.0 ) )
+				{
+					pathTarget = cache[i].target;
+					leadArea = cache[i].pArea;
+					bFound = true;
+					break;
+				}
+			}
+		}
+
+		if ( !bFound )
+		{
+			leadArea = TheNavMesh->GetNearestNavArea( pathTarget );
+			if ( leadArea )
+			{
+				cache[iNext].target = pathTarget;
+				cache[iNext].pArea = leadArea;
+				iNext = ( iNext + 1 ) % ARRAYSIZE( cache );
+			}
+		}
+	}
+#else
+	leadArea = TheNavMesh->GetNearestNavArea( pathTarget );
+#endif
+
+
+	if ( !leadArea || leadArea->GetZ( pathTarget.x, pathTarget.y ) < pathTarget.z - mover->GetMaxJumpHeight() )
+	{
+		// would fall off a cliff
+		return subjectPos;		
+	}
+	
+	/** This needs more thought - it is preventing bots from using dropdowns
+	if ( mover->HasPotentialGap( subjectPos, pathTarget, &fraction ) )
+	{
+		// tried to lead over a cliff - clip to safe region
+		pathTarget = subjectPos + fraction * ( pathTarget - subjectPos );
+	}
+	*/
+	
+	return pathTarget;
+}
+
+// if the victim is a player, poke them so they know they're being chased
+void DirectChasePath::NotifyVictim( INextBot *me, CBaseEntity *victim )
+{
+	CBaseCombatCharacter *pBCCVictim = ToBaseCombatCharacter( victim );
+	if ( !pBCCVictim )
+		return;
+	
+	pBCCVictim->OnPursuedBy( me );
+}