private List <GraphicsPath> GenerateTerrainOutline()
{
// travel around an ellipse, with noise applied to it
// 0.001 to 0.01 seems to work best for noise frequency, 100 works well for noise amplitude
float frequency = 0.005f;
float amplitude = Math.Min(Width, Height) / 2;
var terrainNoiseX = new PerlinNoise(Random.Next(), frequency, amplitude, 4);
var terrainNoiseY = new PerlinNoise(Random.Next(), frequency, amplitude, 4);
var landmasses = new List <List <PointF> >();
var mainland = new List <PointF>();
landmasses.Add(mainland);
var prevPoint = new PointF(Width / 2f, Height / 2f);
float ellipseWidth = Width * 0.75f;
float ellipseHeight = Height * 0.75f;
int step = 0;
for (float angle = (float)Math.PI * 2; angle > 0; angle -= 0.01f /* roughly 500 steps */)
{
step++;
float ellipseX = Width / 2f + (float)Math.Cos(angle) * ellipseWidth / 2;
float ellipseY = Height / 2f + (float)Math.Sin(angle) * ellipseHeight / 2;
float placeX = ellipseX + terrainNoiseX.GetValue(ellipseX, ellipseY);
float placeY = ellipseY + terrainNoiseY.GetValue(ellipseX, ellipseY);
var nextPoint = new PointF(placeX, placeY);
// See if prevPoint - nextPoint crosses ANY of the previous lines. If it does, we have a loop / dangler.
// Ignore the first line and the most recent line, cos we may well touch those.
for (int i = mainland.Count - 3; i > 1; i--)
{
var testEnd = mainland[i - 1];
var testStart = mainland[i];
if (LineSegmentsCross(prevPoint, nextPoint, testStart, testEnd))
{
// Because we are ALWAYS working our way anticlockwise around the main landmass:
// "outties" always have the "older" line cross the "newer" one from left to right.
// "innies" always have the "older" line cross the "newer" one from right to left.
// UNLESS we are dealing with "nested" outties or innies, in which case the direction swaps.
// But maybe its ok to swap what we do there, as we will get larger islands / inlets that way,
// as opposed to "chains" of smaller ones, which are perhaps less important - especially on a political map.
bool chopOff = IsLeftOfLine(prevPoint, nextPoint, testEnd);
HandleTerrainBoundaryLoop(landmasses, mainland, i, chopOff);
break;
}
}
mainland.Add(nextPoint);
prevPoint = nextPoint;
}
ScaleToFitBounds(landmasses);
Landmasses = landmasses
.Select(points =>
{
var types = new byte[points.Count];
for (var i = types.Length - 1; i >= 0; i--)
{
types[i] = 1;
}
return(new GraphicsPath(points.Select(p => new System.Drawing.PointF(p.X, p.Y)).ToArray(), types));
})
.ToList();
return(Landmasses);
}