// Initialization creates a System.Random object and precomputes indices and weights of erosion brush
static void Initialize(int mapSize, bool resetSeed, ErossionSettings erossionSettings, int seed)
{
if (resetSeed || prng == null || currentSeed != seed)
{
prng = new System.Random(seed);
currentSeed = seed;
}
if (erosionBrushIndices == null || currentErosionRadius != erossionSettings.erosionBrushRadius || currentMapSize != mapSize)
{
InitializeBrushIndices(mapSize, erossionSettings.erosionBrushRadius);
currentErosionRadius = erossionSettings.erosionBrushRadius;
currentMapSize = mapSize;
}
}
//----GPU--------------------------
public static float[] ErodeGPU(float[] map, int mapSize, ErossionSettings erossionSettings, ComputeShader erosion)
{
int mapSizeWithBorder = mapSize + erossionSettings.erosionBrushRadius * 2;
int numThreads = erossionSettings.numErosionIterations / 1024;
// Create brush
List <int> brushIndexOffsets = new List <int>();
List <float> brushWeights = new List <float>();
float weightSum = 0;
for (int brushY = -erossionSettings.erosionBrushRadius; brushY <= erossionSettings.erosionBrushRadius; brushY++)
{
for (int brushX = -erossionSettings.erosionBrushRadius; brushX <= erossionSettings.erosionBrushRadius; brushX++)
{
float sqrDst = brushX * brushX + brushY * brushY;
if (sqrDst < erossionSettings.erosionBrushRadius * erossionSettings.erosionBrushRadius)
{
brushIndexOffsets.Add(brushY * mapSize + brushX);
float brushWeight = 1 - Mathf.Sqrt(sqrDst) / erossionSettings.erosionBrushRadius;
weightSum += brushWeight;
brushWeights.Add(brushWeight);
}
}
}
for (int i = 0; i < brushWeights.Count; i++)
{
brushWeights[i] /= weightSum;
}
// Send brush data to compute shader
ComputeBuffer brushIndexBuffer = new ComputeBuffer(brushIndexOffsets.Count, sizeof(int));
ComputeBuffer brushWeightBuffer = new ComputeBuffer(brushWeights.Count, sizeof(int));
brushIndexBuffer.SetData(brushIndexOffsets);
brushWeightBuffer.SetData(brushWeights);
erosion.SetBuffer(0, "brushIndices", brushIndexBuffer);
erosion.SetBuffer(0, "brushWeights", brushWeightBuffer);
// Generate random indices for droplet placement
int[] randomIndices = new int[erossionSettings.numErosionIterations];
for (int i = 0; i < erossionSettings.numErosionIterations; i++)
{
int randomX = Random.Range(erossionSettings.erosionBrushRadius, mapSize + erossionSettings.erosionBrushRadius);
int randomY = Random.Range(erossionSettings.erosionBrushRadius, mapSize + erossionSettings.erosionBrushRadius);
randomIndices[i] = randomY * mapSize + randomX;
}
// Send random indices to compute shader
ComputeBuffer randomIndexBuffer = new ComputeBuffer(randomIndices.Length, sizeof(int));
randomIndexBuffer.SetData(randomIndices);
erosion.SetBuffer(0, "randomIndices", randomIndexBuffer);
// Heightmap buffer
ComputeBuffer mapBuffer = new ComputeBuffer(map.Length, sizeof(float));
mapBuffer.SetData(map);
erosion.SetBuffer(0, "map", mapBuffer);
// Settings
erosion.SetInt("borderSize", erossionSettings.erosionBrushRadius);
erosion.SetInt("mapSize", mapSizeWithBorder);
erosion.SetInt("brushLength", brushIndexOffsets.Count);
erosion.SetInt("maxLifetime", erossionSettings.maxLifetime);
erosion.SetFloat("inertia", erossionSettings.inertia);
erosion.SetFloat("sedimentCapacityFactor", erossionSettings.sedimentCapacityFactor);
erosion.SetFloat("minSedimentCapacity", erossionSettings.minSedimentCapacity);
erosion.SetFloat("depositSpeed", erossionSettings.depositSpeed);
erosion.SetFloat("erodeSpeed", erossionSettings.erodeSpeed);
erosion.SetFloat("evaporateSpeed", erossionSettings.evaporateSpeed);
erosion.SetFloat("gravity", erossionSettings.gravity);
erosion.SetFloat("startSpeed", erossionSettings.startSpeed);
erosion.SetFloat("startWater", erossionSettings.startWater);
// Run compute shader
erosion.Dispatch(0, numThreads, 1, 1);
mapBuffer.GetData(map);
// Release buffers
mapBuffer.Release();
randomIndexBuffer.Release();
brushIndexBuffer.Release();
brushWeightBuffer.Release();
return(map);
}
public static float[] ErodeCPU(float[] map, int mapSize, ErossionSettings erossionSettings, int seed)
{
bool resetSeed = false;
Initialize(mapSize, resetSeed, erossionSettings, seed);
for (int iteration = 0; iteration < erossionSettings.numErosionIterations; iteration++)
{
// Create water droplet at random point on map
float posX = prng.Next(0, mapSize - 1);
float posY = prng.Next(0, mapSize - 1);
float dirX = 0;
float dirY = 0;
float speed = erossionSettings.startSpeed;
float water = erossionSettings.startWater;
float sediment = 0;
for (int lifetime = 0; lifetime < erossionSettings.maxLifetime; lifetime++)
{
int nodeX = (int)posX;
int nodeY = (int)posY;
int dropletIndex = nodeY * mapSize + nodeX;
// Calculate droplet's offset inside the cell (0,0) = at NW node, (1,1) = at SE node
float cellOffsetX = posX - nodeX;
float cellOffsetY = posY - nodeY;
// Calculate droplet's height and direction of flow with bilinear interpolation of surrounding heights
HeightAndGradient heightAndGradient = CalculateHeightAndGradient(map, mapSize, posX, posY);
// Update the droplet's direction and position (move position 1 unit regardless of speed)
dirX = (dirX * erossionSettings.inertia - heightAndGradient.gradientX * (1 - erossionSettings.inertia));
dirY = (dirY * erossionSettings.inertia - heightAndGradient.gradientY * (1 - erossionSettings.inertia));
// Normalize direction
float len = Mathf.Sqrt(dirX * dirX + dirY * dirY);
if (len != 0)
{
dirX /= len;
dirY /= len;
}
posX += dirX;
posY += dirY;
// Stop simulating droplet if it's not moving or has flowed over edge of map
if ((dirX == 0 && dirY == 0) || posX < 0 || posX >= mapSize - 1 || posY < 0 || posY >= mapSize - 1)
{
break;
}
// Find the droplet's new height and calculate the deltaHeight
float newHeight = CalculateHeightAndGradient(map, mapSize, posX, posY).height;
float deltaHeight = newHeight - heightAndGradient.height;
// Calculate the droplet's sediment capacity (higher when moving fast down a slope and contains lots of water)
float sedimentCapacity = Mathf.Max(-deltaHeight * speed * water * erossionSettings.sedimentCapacityFactor, erossionSettings.minSedimentCapacity);
// If carrying more sediment than capacity, or if flowing uphill:
if (sediment > sedimentCapacity || deltaHeight > 0)
{
// If moving uphill (deltaHeight > 0) try fill up to the current height, otherwise deposit a fraction of the excess sediment
float amountToDeposit = (deltaHeight > 0) ? Mathf.Min(deltaHeight, sediment) : (sediment - sedimentCapacity) * erossionSettings.depositSpeed;
sediment -= amountToDeposit;
// Add the sediment to the four nodes of the current cell using bilinear interpolation
// Deposition is not distributed over a radius (like erosion) so that it can fill small pits
map[dropletIndex] += amountToDeposit * (1 - cellOffsetX) * (1 - cellOffsetY);
map[dropletIndex + 1] += amountToDeposit * cellOffsetX * (1 - cellOffsetY);
map[dropletIndex + mapSize] += amountToDeposit * (1 - cellOffsetX) * cellOffsetY;
map[dropletIndex + mapSize + 1] += amountToDeposit * cellOffsetX * cellOffsetY;
}
else
{
// Erode a fraction of the droplet's current carry capacity.
// Clamp the erosion to the change in height so that it doesn't dig a hole in the terrain behind the droplet
float amountToErode = Mathf.Min((sedimentCapacity - sediment) * erossionSettings.erodeSpeed, -deltaHeight);
// Use erosion brush to erode from all nodes inside the droplet's erosion radius
for (int brushPointIndex = 0; brushPointIndex < erosionBrushIndices[dropletIndex].Length; brushPointIndex++)
{
int nodeIndex = erosionBrushIndices[dropletIndex][brushPointIndex];
float weighedErodeAmount = amountToErode * erosionBrushWeights[dropletIndex][brushPointIndex];
float deltaSediment = (map[nodeIndex] < weighedErodeAmount) ? map[nodeIndex] : weighedErodeAmount;
map[nodeIndex] -= deltaSediment;
sediment += deltaSediment;
}
}
// Update droplet's speed and water content
speed = Mathf.Sqrt(speed * speed + deltaHeight * erossionSettings.gravity);
water *= (1 - erossionSettings.evaporateSpeed);
}
}
return(map);
}
