Method CreateLakeImage

src/Generating/StructGen.cpp:443–529

void cStructGenLakes::CreateLakeImage(int a_ChunkX, int a_ChunkZ, cBlockArea & a_Lake)
{
	a_Lake.Create(16, 8, 16);
	a_Lake.Fill(cBlockArea::baTypes, E_BLOCK_SPONGE);  // Sponge is the NOP blocktype for lake merging strategy
	
	// Find the minimum height in this chunk:
	cChunkDef::HeightMap HeightMap;
	m_HeiGen.GenHeightMap(a_ChunkX, a_ChunkZ, HeightMap);
	HEIGHTTYPE MinHeight = HeightMap[0];
	for (size_t i = 1; i < ARRAYCOUNT(HeightMap); i++)
	{
		if (HeightMap[i] < MinHeight)
		{
			MinHeight = HeightMap[i];
		}
	}
	
	// Make a random position in the chunk by using a random 16 block XZ offset and random height up to chunk's max height minus 6
	MinHeight = std::max(MinHeight - 6, 2);
	int Rnd = m_Noise.IntNoise3DInt(a_ChunkX, 128, a_ChunkZ) / 11;
	// Random offset [-8 .. 8], with higher probability around 0; add up four three-bit-wide randoms [0 .. 28], divide and subtract to get range
	int OffsetX = 4 * ((Rnd & 0x07) + ((Rnd & 0x38) >> 3) + ((Rnd & 0x1c0) >> 6) + ((Rnd & 0xe00) >> 9)) / 7 - 8;
	Rnd >>= 12;
	// Random offset [-8 .. 8], with higher probability around 0; add up four three-bit-wide randoms [0 .. 28], divide and subtract to get range
	int OffsetZ = 4 * ((Rnd & 0x07) + ((Rnd & 0x38) >> 3) + ((Rnd & 0x1c0) >> 6) + ((Rnd & 0xe00) >> 9)) / 7 - 8;
	Rnd = m_Noise.IntNoise3DInt(a_ChunkX, 512, a_ChunkZ) / 13;
	// Random height [1 .. MinHeight] with preference to center heights
	int HeightY = 1 + (((Rnd & 0x1ff) % MinHeight) + (((Rnd >> 9) & 0x1ff) % MinHeight)) / 2;
	
	a_Lake.SetOrigin(OffsetX, HeightY, OffsetZ);
	
	// Hollow out a few bubbles inside the blockarea:
	int NumBubbles = 4 + ((Rnd >> 18) & 0x03);  // 4 .. 7 bubbles
	BLOCKTYPE * BlockTypes = a_Lake.GetBlockTypes();
	for (int i = 0; i < NumBubbles; i++)
	{
		int Rnd = m_Noise.IntNoise3DInt(a_ChunkX, i, a_ChunkZ) / 13;
		const int BubbleR = 2 + (Rnd & 0x03);  // 2 .. 5
		const int Range = 16 - 2 * BubbleR;
		const int BubbleX = BubbleR + (Rnd % Range);
		Rnd >>= 4;
		const int BubbleY = 4 + (Rnd & 0x01);  // 4 .. 5
		Rnd >>= 1;
		const int BubbleZ = BubbleR + (Rnd % Range);
		Rnd >>= 4;
		const int HalfR = BubbleR / 2;  // 1 .. 2
		const int RSquared = BubbleR * BubbleR;
		for (int y = -HalfR; y <= HalfR; y++)
		{
			// BubbleY + y is in the [0, 7] bounds
			int DistY = 4 * y * y / 3;
			int IdxY = (BubbleY + y) * 16 * 16;
			for (int z = -BubbleR; z <= BubbleR; z++)
			{
				int DistYZ = DistY + z * z;
				if (DistYZ >= RSquared)
				{
					continue;