/// <summary>
/// Gets a normal vector for a given x, z coordinate and the corresponding heightmap
/// </summary>
/// <param name="heightMap"></param>
/// <param name="x"></param>
/// <param name="z"></param>
/// <returns></returns>
private static Vector4 GetNormalVector(HeightMap heightMap, int x, int z)
{
var currentP = new Vector3(x, heightMap.GetScaledHeight(x, z), z);
Vector3 p1;
Vector3 p2;
if (x == heightMap.Size - 1 && z == heightMap.Size - 1) // Bottom right pixel
{
p1 = new Vector3(x, heightMap.GetScaledHeight(x, z - 1), z - 1);
p2 = new Vector3(x - 1, heightMap.GetScaledHeight(x - 1, z), z);
}
else if (x == heightMap.Size - 1) // Right border
{
p1 = new Vector3(x - 1, heightMap.GetScaledHeight(x - 1, z), z);
p2 = new Vector3(x, heightMap.GetScaledHeight(x, z + 1), z + 1);
}
else if (z == heightMap.Size - 1) // Bottom border
{
p1 = new Vector3(x + 1, heightMap.GetScaledHeight(x + 1, z), z);
p2 = new Vector3(x, heightMap.GetScaledHeight(x, z - 1), z - 1);
}
else // The rest of pixels
{
p1 = new Vector3(x, heightMap.GetScaledHeight(x, z + 1), z + 1);
p2 = new Vector3(x + 1, heightMap.GetScaledHeight(x + 1, z), z);
}
return(new Vector4(Vector3.Normalize(Vector3.Cross(p1 - currentP, p2 - currentP)), 1));
}
/// <summary>
/// Initializes Vertex buffer data by a given heightmap
/// </summary>
/// <param name="heightMap"></param>
/// <param name="vertexBuffer"></param>
private static unsafe void SetVertexDataFromHeightMap(HeightMap heightMap, IntPtr vertexBuffer)
{
var vb = (VertexNormalTexture *)vertexBuffer;
var halfSize = heightMap.Size * 0.5f;
for (var iZ = 0; iZ < heightMap.Size; ++iZ)
{
for (var iX = 0; iX < heightMap.Size; ++iX)
{
vb[iZ * heightMap.Size + iX] = new VertexNormalTexture
{
Position = new Vector4(iX - halfSize, heightMap.GetScaledHeight(iX, iZ), -iZ + halfSize, 1),
Normal = GetNormalVector(heightMap, iX, iZ),
TextureCoordinate = new Vector2((float)iX / heightMap.Size, (float)iZ / heightMap.Size)
};
}
}
}
