nX * IMAGE_SIZE) - 3) & -BLOCK_SIZE, 0), img.width - READ_SIZE);
					// offset up from click and make multiple of block size.
					const offsetY = Math.min(Math.max((Math.floor(fractionY * IMAGE_SIZE) - 3) & -BLOCK_SIZE, 0), img.height - READ_SIZE);
					// Note: the bounding logic above will cause artifacts clicking along the terrain edges

					terrainHeightFieldShape.GetHeights(offsetX, offsetY, READ_SIZE, READ_SIZE, float32MemPointer, READ_SIZE)

					// Apply a flat amount of modification to all pixel