fix(partition): Fix circle fill algorithm in PartitionManager (#1426)

This reduces its cost by around 10%

Author: Stubbjax

Generals/Code/GameEngine/Source/GameLogic/Object/PartitionManager.cpp

@@ -1838,6 +1838,8 @@ void PartitionData::hLineCircle(Int x1, Int x2, Int y)
 }
 
 // -----------------------------------------------------------------------------
+// Marks all partition cells that intersect a circle of the given center and radius
+// as covered by this object using a variation of the midpoint circle algorithm.
 void PartitionData::doCircleFill(
 	Real centerX,
 	Real centerY,
@@ -1855,7 +1857,15 @@ void PartitionData::doCircleFill(
 
 	Int y = cellRadius - 1;
 	Int dec = 3 - 2*cellRadius;
-	for (Int x = 0; x < cellRadius; x++)
+
+#if RETAIL_COMPATIBLE_CRC
+	// Cell coverage diverges at radii >= 240 between algorithms.
+	Int end = cellRadius - 1;
+	Int& endRef = (cellRadius < 240) ? y : end;
+	for (Int x = 0; x <= endRef; ++x)
+#else
+	for (Int x = 0; x <= y; ++x)
+#endif
 	{
 		hLineCircle(cellCenterX - x, cellCenterX + x, cellCenterY + y);
 		hLineCircle(cellCenterX - x, cellCenterX + x, cellCenterY - y);

GeneralsMD/Code/GameEngine/Source/GameLogic/Object/PartitionManager.cpp

@@ -1842,6 +1842,8 @@ void PartitionData::hLineCircle(Int x1, Int x2, Int y)
 }
 
 // -----------------------------------------------------------------------------
+// Marks all partition cells that intersect a circle of the given center and radius
+// as covered by this object using a variation of the midpoint circle algorithm.
 void PartitionData::doCircleFill(
 	Real centerX,
 	Real centerY,
@@ -1859,7 +1861,15 @@ void PartitionData::doCircleFill(
 
 	Int y = cellRadius - 1;
 	Int dec = 3 - 2*cellRadius;
-	for (Int x = 0; x < cellRadius; x++)
+
+#if RETAIL_COMPATIBLE_CRC
+	// Cell coverage diverges at radii >= 240 between algorithms.
+	Int end = cellRadius - 1;
+	Int& endRef = (cellRadius < 240) ? y : end;
+	for (Int x = 0; x <= endRef; ++x)
+#else
+	for (Int x = 0; x <= y; ++x)
+#endif
 	{
 		hLineCircle(cellCenterX - x, cellCenterX + x, cellCenterY + y);
 		hLineCircle(cellCenterX - x, cellCenterX + x, cellCenterY - y);