tile_map.cpp

Go to the documentation of this file.

/* $Id: tile_map.cpp 14502 2008-10-20 15:44:14Z rubidium $ */

#include "stdafx.h"
#include "openttd.h"
#include "tile_map.h"
#include "core/math_func.hpp"

Slope GetTileSlope(TileIndex tile, uint *h)
{
  assert(tile < MapSize());

  if (TileX(tile) == MapMaxX() || TileY(tile) == MapMaxY()) {
    if (h != NULL) *h = 0;
    return SLOPE_FLAT;
  }

  uint a = TileHeight(tile); // Height of the N corner
  uint min = a; // Minimal height of all corners examined so far
  uint b = TileHeight(tile + TileDiffXY(1, 0)); // Height of the W corner
  if (min > b) min = b;
  uint c = TileHeight(tile + TileDiffXY(0, 1)); // Height of the E corner
  if (min > c) min = c;
  uint d = TileHeight(tile + TileDiffXY(1, 1)); // Height of the S corner
  if (min > d) min = d;

  /* Due to the fact that tiles must connect with each other without leaving gaps, the
   * biggest difference in height between any corner and 'min' is between 0, 1, or 2.
   *
   * Also, there is at most 1 corner with height difference of 2.
   */

  uint r = SLOPE_FLAT; // Computed slope of the tile

  /* For each corner if not equal to minimum height:
   *  - set the SLOPE_STEEP flag if the difference is 2
   *  - add the corresponding SLOPE_X constant to the computed slope
   */
  if ((a -= min) != 0) r += (--a << 4) + SLOPE_N;
  if ((c -= min) != 0) r += (--c << 4) + SLOPE_E;
  if ((d -= min) != 0) r += (--d << 4) + SLOPE_S;
  if ((b -= min) != 0) r += (--b << 4) + SLOPE_W;

  if (h != NULL) *h = min * TILE_HEIGHT;

  return (Slope)r;
}

uint GetTileZ(TileIndex tile)
{
  if (TileX(tile) == MapMaxX() || TileY(tile) == MapMaxY()) return 0;

  uint h = TileHeight(tile); // N corner
  h = min(h, TileHeight(tile + TileDiffXY(1, 0))); // W corner
  h = min(h, TileHeight(tile + TileDiffXY(0, 1))); // E corner
  h = min(h, TileHeight(tile + TileDiffXY(1, 1))); // S corner

  return h * TILE_HEIGHT;
}

uint GetTileMaxZ(TileIndex t)
{
  if (TileX(t) == MapMaxX() || TileY(t) == MapMaxY()) return 0;

  uint h = TileHeight(t); // N corner
  h = max(h, TileHeight(t + TileDiffXY(1, 0))); // W corner
  h = max(h, TileHeight(t + TileDiffXY(0, 1))); // E corner
  h = max(h, TileHeight(t + TileDiffXY(1, 1))); // S corner

  return h * TILE_HEIGHT;
}