public PackedHexagonalGrid(int width, int height, int padding, float spacing)
{
Width = width;
Height = height;
Padding = padding;
Spacing = spacing;
var grid = new FancyHexagonalGrid(spacing);
var vertices = CreateVertices(grid, width, height, padding);
VerticesX = vertices.Select(v => v.X).ToArray();
VerticesY = vertices.Select(v => v.Y).ToArray();
}
// Create a width x height array of vertices in row-major order
// Each row is padded with VectorSize extra elements on both sides
private static Vector2[] CreateVertices(FancyHexagonalGrid grid, int width, int height, int padding)
{
int doublePadding = 2 * padding;
int stride = width + doublePadding;
var vertices = new Vector2[stride * height];
// Initialize the array with NaNs.
for (int i = 0; i < vertices.Length; i++)
vertices[i] = new Vector2(AllOnes);
// Loop invariant: index = padding + row * stride + col
//
// Before loop: index = padding, row = 0, col = 0. Invariant holds.
int index = padding;
for (int row = 0; row < height; row++)
{
for (int col = 0; col < width; col++)
{
vertices[index] = grid.GetVertex(col, row);
index++;
// after col++:
// col' = col + 1
// index' = index + 1 = padding + row * stride + col + 1
// = padding + row * stride + col'
// Invariant holds.
}
// col = width
// index = padding + row * stride + width
index += doublePadding;
// after row++ and col = 0
// index' = index + doublePadding
// = padding + row * stride + width + doublePadding
// = padding + row * stride + stride (stride = width + doublePadding)
// = padding + row' * stride + col (col = 0, row' = row + 1)
// Invariant holds.
}
return vertices;
}
