From db682395bbb6322ebd72f857ead4fb1161ade39f Mon Sep 17 00:00:00 2001
From: Marcus Hutchings <github-2843@nevermore.plus.com>
Date: Tue, 13 Sep 2022 07:54:55 +0100
Subject: [PATCH] Added customisable update rate for unit quad positions to
 reduce CPU load.

---
 rts/Sim/Misc/ModInfo.cpp       | 2 ++
 rts/Sim/Misc/ModInfo.h         | 4 ++++
 rts/Sim/MoveTypes/MoveType.cpp | 5 +++++
 3 files changed, 11 insertions(+)

diff --git a/rts/Sim/Misc/ModInfo.cpp b/rts/Sim/Misc/ModInfo.cpp
index 82dd8ebf3b..f953ad65e2 100644
--- a/rts/Sim/Misc/ModInfo.cpp
+++ b/rts/Sim/Misc/ModInfo.cpp
@@ -35,6 +35,7 @@ void CModInfo::ResetState()
 		allowHoverUnitStrafing     = true;
 
 		maxCollisionPushMultiplier = std::numeric_limits<float>::infinity();
+		unitQuadPositionUpdateRate = 3;
 	}
 	{
 		constructionDecay      = true;
@@ -161,6 +162,7 @@ void CModInfo::Init(const std::string& modFileName)
 		allowGroundUnitGravity = movementTbl.GetBool("allowGroundUnitGravity", allowGroundUnitGravity);
 		allowHoverUnitStrafing = movementTbl.GetBool("allowHoverUnitStrafing", (pathFinderSystem == QTPFS_TYPE));
 		maxCollisionPushMultiplier = movementTbl.GetFloat("maxCollisionPushMultiplier", maxCollisionPushMultiplier);
+		unitQuadPositionUpdateRate = movementTbl.GetInt("unitQuadPositionUpdateRate",  unitQuadPositionUpdateRate);
 	}
 
 	{
diff --git a/rts/Sim/Misc/ModInfo.h b/rts/Sim/Misc/ModInfo.h
index 9c3334831e..d58899a33e 100644
--- a/rts/Sim/Misc/ModInfo.h
+++ b/rts/Sim/Misc/ModInfo.h
@@ -55,6 +55,10 @@ class CModInfo
 	// relative to a unit's maxspeed (default: inf)
 	float maxCollisionPushMultiplier;
 
+	// rate in sim frames that a unit's position in the quad grid is updated (default: 3)
+	// lower the number will increase CPU load, but increase accuracy of collision detection
+	int unitQuadPositionUpdateRate;
+
 	// Build behaviour
 	/// Should constructions without builders decay?
 	bool constructionDecay;
diff --git a/rts/Sim/MoveTypes/MoveType.cpp b/rts/Sim/MoveTypes/MoveType.cpp
index 3e2eecce74..4aa75f6d79 100644
--- a/rts/Sim/MoveTypes/MoveType.cpp
+++ b/rts/Sim/MoveTypes/MoveType.cpp
@@ -5,6 +5,8 @@
 
 #include "MoveType.h"
 #include "Map/Ground.h"
+#include "Sim/Misc/GlobalSynced.h"
+#include "Sim/Misc/ModInfo.h"
 #include "Sim/Misc/QuadField.h"
 #include "Sim/Units/Unit.h"
 #include "Sim/Units/UnitDef.h"
@@ -72,6 +74,9 @@ AMoveType::AMoveType(CUnit* owner):
 
 void AMoveType::UpdateCollisionMap()
 {
+	if ((gs->frameNum + owner->id) % modInfo.unitQuadPositionUpdateRate)
+		return;
+
 	if (owner->pos != oldSlowUpdatePos) {
 		const int newMapSquare = CGround::GetSquare(oldSlowUpdatePos = owner->pos);