void applyErosion(ref Droplet d, ref float[] map, ref bool[] updated, float erosionAmount)
{
int radius = Vars.pErosionRadius;
double[] weights = new double[(int)Math.Pow(2 * radius + 1, 2)];
Vector2[] coords = new Vector2[(int)Math.Pow(2 * radius + 1, 2)];
int numPoint = 0;
double weighSum = 0;
for (int x = -radius; x <= radius + 1; ++x)
{
for (int y = -radius; y <= radius + 1; ++y)
{
int coordX = (int)d.x + x;
int coordY = (int)d.y + y;
float diffX = coordX - d.x, diffY = coordY - d.y;
float distanceSqrd = x * x + y * y;
// ignore points outside the circle
if (distanceSqrd > radius * radius)
{
continue;
}
if (coordX >= 0 && coordX < Vars.imgRes && coordY >= 0 && coordY < Vars.imgRes)
{
double weight = Math.Max(0, radius - Math.Sqrt(distanceSqrd));
weights[numPoint] = weight;
coords[numPoint] = new Vector2(coordX, coordY);
numPoint++;
weighSum += weight;
}
}
}
for (int i = 0; i < numPoint; ++i)
{
weights[i] /= weighSum;
float pointErosion = (float)(erosionAmount * weights[i]);
int pointIndex = (int)(coords[i].x * Vars.imgRes + coords[i].y);
updated[pointIndex] = true;
if (pointErosion > map[pointIndex])
{
d.sediment += map[pointIndex];
map[pointIndex] = 0;
}
else
{
d.sediment += pointErosion;
map[pointIndex] -= pointErosion;
}
}
}
void computeGradientHeight(float[] mapHeights, ref Droplet d, ref float dropletHeight, ref Vector2 gradient)
{
// get the upper left corner of the enclosing quad
int xGrid = (int)Math.Floor(d.x), yGrid = (int)Math.Floor(d.y);
// get droplet position inside the quad
d.u = d.x - xGrid;
d.v = d.y - yGrid;
// get the heights of the quad corners
float xy = mapHeights[xGrid * Vars.imgRes + yGrid];
float x1y = mapHeights[(xGrid + 1) * Vars.imgRes + yGrid];
float xy1 = mapHeights[xGrid * Vars.imgRes + yGrid + 1];
float x1y1 = mapHeights[(xGrid + 1) * Vars.imgRes + yGrid + 1];
// get droplet height by bilinear interpolation of the enclosing quad corners
dropletHeight = (x1y1 * d.u + x1y * (1 - d.u)) * d.v + (xy1 * d.u + xy * (1 - d.v)) * (1 - d.v);
gradient = new Vector2(
(x1y - xy) * (1 - d.v) + (x1y1 - xy1) * d.v,
(xy1 - xy) * (1 - d.u) + (x1y1 - x1y) * d.u);
}
public void Update(int miniIts = 100, bool ret = false)
{
for (int i = 0; i < miniIts; i++)
{
Droplet d = new Droplet();
for (int j = 0; j < Vars.nrIterations; j++)
{
Vector2 oldPos = new Vector2(d.x, d.y);
int xGrid = (int)Math.Floor(d.x), yGrid = (int)Math.Floor(d.y);
float offsetX = d.x - xGrid;
float offsetY = d.y - yGrid;
// get droplet height by bilinear interpolation of the enclosing quad
float dHeight = 0;
Vector2 gradient = new Vector2(0, 0);
computeGradientHeight(updatedHeights, ref d, ref dHeight, ref gradient);
// get new direction and normalize
d.dir.x = (d.dir.x * Vars.pInertia - gradient.x * (1 - Vars.pInertia));
d.dir.y = (d.dir.y * Vars.pInertia - gradient.y * (1 - Vars.pInertia));
d.dir.Normalize();
Console.WriteLine(d.dir);
// update position
d.x += d.dir.x;
d.y += d.dir.y;
// stop simulating droplet if it doesn't move or if it gets out of bounds
if ((d.dir.x == 0 && d.dir.y == 0) || d.x < 0 || d.x >= (Vars.imgRes - 1) || d.y < 0 || d.y >= (Vars.imgRes - 1))
{
break;
}
// compute new droplet height
float newHeight = 0;
Vector2 newGradient = new Vector2(0, 0);
computeGradientHeight(updatedHeights, ref d, ref newHeight, ref newGradient);
float heightDiff = newHeight - dHeight;
float c = Math.Max(-heightDiff, Vars.pMinSlope) * d.velocity * d.water * Vars.pCapacity;
// droplet is moving uphill or has more sediment than its capacity
if (d.sediment > c)
{
// Deposit sediment
float depositAmount = (d.sediment - c) * Vars.pDeposition;
applyDeposition(ref d, ref updatedHeights, ref updatedPixel, depositAmount, newHeight);
}
else if (heightDiff > 0)
{
float depositAmount = Math.Min(heightDiff, d.sediment);
applyDeposition(ref d, ref updatedHeights, ref updatedPixel, depositAmount, dHeight, true, oldPos.x, oldPos.y);
}
else
{
// Erode all points inside the radius
float erosionAmount = Math.Min((c - d.sediment) * Vars.pErosion, -heightDiff);
applyErosion(ref d, ref updatedHeights, ref updatedPixel, erosionAmount);
}
// update droplet velocity and water amount
d.velocity = (float)Math.Sqrt(Math.Max(d.velocity * d.velocity - heightDiff * Vars.pGravity, 0));
d.water = d.water * (1 - Vars.pEvaporation);
}
Vars.currentDroplets++;
}
if (ret)
{
updatedHeights = blurMap(updatedHeights, Vars.imgRes, updatedPixel);
updatedPixel = new bool[updatedHeights.Length];
}
}
void applyDeposition(ref Droplet d, ref float[] map, ref bool[] updated, float depositAmount, float currHeight, bool tooHigh = false, float oldX = 0, float oldY = 0)
{
float X = d.x, Y = d.y;
// We want to deposit before the hill, not on the hill
if (tooHigh)
{
X = oldX;
Y = oldY;
}
int radius = Vars.pErosionRadius;
List <double> distanceWeights = new List <double>();
List <double> heightWeights = new List <double>();
List <Vector2> coords = new List <Vector2>();
int numPoint = 0;
double dWeightSum = 0, hWeightSum = 0;
for (int x = -radius; x <= radius + 1; ++x)
{
for (int y = -radius; y <= radius + 1; ++y)
{
int coordX = (int)X + x;
int coordY = (int)Y + y;
float diffX = coordX - X, diffY = coordY - Y;
float distanceSqrd = diffX * diffX + diffY * diffY;
// ignore points outside the circle
if (distanceSqrd > radius * radius)
{
continue;
}
if (coordX >= 0 && coordX < Vars.imgRes && coordY >= 0 && coordY < Vars.imgRes)
{
float hDiff = map[coordX * Vars.imgRes + coordY] - currHeight;
double distanceWeight = Math.Max(0, radius - Math.Sqrt(distanceSqrd));
distanceWeights.Add(distanceWeight);
// higher points recieve exponentially less deposition
double heightWeight = Math.Pow(1 - hDiff, 2);
heightWeights.Add(heightWeight);
coords.Add(new Vector2(coordX, coordY));
numPoint++;
dWeightSum += distanceWeight;
hWeightSum += heightWeight;
}
}
}
for (int i = 0; i < numPoint; ++i)
{
distanceWeights[i] /= dWeightSum;
heightWeights[i] /= hWeightSum;
double weight = (distanceWeights[i] + heightWeights[i]) / 2;
float pointDeposition = (float)(depositAmount * weight);
int pointIndex = (int)(coords[i].x * Vars.imgRes + coords[i].y);
d.sediment -= pointDeposition;
map[pointIndex] += pointDeposition;
updated[pointIndex] = true;
}
}