- idx < Width() * Height() || // low Z plane
- idx % Width() == 0 || // low X plane
- (idx / (Width() * Height())) == Depth() - 1 || // high Z plane
- idx % Width() == Width() - 1 || // high X plane
- (idx / Width()) % Height() == 0 || // low Y plane
- (idx / Width()) % Height() == Height() - 1; // high Y plane
+ idx < width * height || // low Z plane
+ idx % width == 0 || // low X plane
+ (idx / (width * height)) == depth - 1 || // high Z plane
+ idx % width == width - 1 || // high X plane
+ (idx / width) % height == 0 || // low Y plane
+ (idx / width) % height == height - 1; // high Y plane