public static Vector3 CalculateNormal(HeightSampler sampler, float x, float y, float d = 1.0f)
{
float dy0 = sampler(x + d, y) - sampler(x - d, y);
float dy1 = sampler(x, y + d) - sampler(x, y - d);
Vector3 result = new Vector3(-dy0, d, -dy1);
result.Normalize();
return result;
}
public static Vector3 CalculateTangent(HeightSampler sampler, float x, float y, float d = 1.0f)
{
float dy0 = sampler(x + d, y) - sampler(x - d, y);
Vector3 result = new Vector3(d * 2.0f, dy0, 0.0f);
result.Normalize();
return result;
//return Vector3.UnitX;
}
public static Mesh BuildHeightmap(HeightSampler sampler, int width, int height, float tilesize, int subdivide = 1)
{
// Determine sizes
int totalW = width * subdivide;
int totalH = height * subdivide;
float invtotalW = 1.0f / totalW;
float invtotalH = 1.0f / totalH;
// Precache an array of heights
float[,] heights = new float[totalW, totalH];
for (int x = 0; x < totalW; x++)
{
float fX = x * invtotalW * width;
for (int y = 0; y < totalH; y++)
{
float fY = y * invtotalH * height;
heights[x, y] = sampler(fX, fY);
}
}
// Recreate the sampler to use the cache
sampler = new HeightSampler((x, y) =>
{
int ix = (int)(x * subdivide);
int iy = (int)(y * subdivide);
if (ix < 0) ix = 0; if (iy < 0) iy = 0;
if (ix >= totalW) ix = totalW - 1;
if (iy >= totalH) iy = totalH - 1;
return heights[ix, iy];
});
// Prepare the builder
MeshBuilder builder = new MeshBuilder();
builder.UseNormals = true;
builder.UseTangents = true;
// Perform the loop
for (int x = 0; x < totalW; x++)
{
float fX = x * invtotalW * width;
for (int y = 0; y < totalH; y++)
{
float fY = y * invtotalH * height;
builder.AddPosition(new Vector3(fX * tilesize, sampler(fX, fY), fY * tilesize));
builder.AddNormal(CalculateNormal(sampler, fX, fY));
builder.AddTangent(CalculateTangent(sampler, fX, fY));
if ((x < totalW - 1) && (y < totalH - 1))
{
int idx = (x * totalH) + y;
builder.AddIndex((ushort)idx);
builder.AddIndex((ushort)(idx + 1));
builder.AddIndex((ushort)(idx + totalH + 1));
builder.AddIndex((ushort)(idx + totalH + 1));
builder.AddIndex((ushort)(idx + totalH));
builder.AddIndex((ushort)idx);
}
}
}
return builder.Build();
}