I've been looking at a couple of games and noticed that the transitions between tiles are handled somewhat different.

I was wondering which methods are to be used in different situations and why. I'm currently using internal edges in a top-down game, and it's working out so far. But I don't want to run into problems later on, and have to redo the whole tileset.

I noticed that platforming games mostly use the internal edges, and top-down games mostly use external and hybrid transitions. I can see how these tiles are used to create "depth" in top-down games, where the player apears to be standing in front of a wall for example. But it seems unlikely that such a small feature decides the entire method for tile transitions. You could always alter the bounding box to create the same effect.


1 Answer 1


On the one hand, your distinction between internal and external transitions looks like kind of a false dichotomy to me. In both cases what you have is tiles depicting a transition from two types of terrain, say sand and water. The only difference is how much sand is depicted vs. how much water. That isn't any sort of technical distinction, just a difference in how the artists choose to draw the tiles.

That said, the main technical difference I would expect from different tiling choices would be in collision detection. For example, if the character moves through water but not sand, then is this transition tile considered water or sand? However this is similar to the case you pointed out in your question, a technical situation that could easily be addressed by altering the bounding box of the tiles.

  • \$\begingroup\$ The main difference between internal and external is that the tile "edge" is either inside the tile, or moved to the next tile. The sample might not really be that clear, sorry. \$\endgroup\$
    – omgnoseat
    Apr 15, 2012 at 18:08
  • 2
    \$\begingroup\$ @omgnoseat read the answer again. The edge doesn't matter. Would a half-dirt-half-water tile be internal or external? \$\endgroup\$
    – kaoD
    Apr 15, 2012 at 18:20
  • \$\begingroup\$ Exactly, that half-and-half example gets at the point I was making. Or think of it this way: look at the bottom tiles of your "external" example. You are saying the water-to-sand transition is external to the sand tiles, but couldn't you just as easily say the water-to-sand transition is internal to the water tiles? \$\endgroup\$
    – jhocking
    Apr 15, 2012 at 18:29
  • \$\begingroup\$ Haha true, didn't look at it that way. \$\endgroup\$
    – omgnoseat
    Apr 15, 2012 at 20:47
  • \$\begingroup\$ But there is one more interesting case of the "external" transition, when the transition takes more than one tile. The most common case of that is with walls that are two tiles high -- the transition between the floor and the wall then takes two tiles -- the front face of the wall, and the top of the wall. \$\endgroup\$ Jan 1, 2013 at 23:03

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