First off, I'm pretty new to the whole game programming thing.
I've been successful with my class's assignments so far, which have all been fairly simple for me. Finally, we are moving into some cool material...

Our final assignment for the semester is to make a platform scroller with multiple levels, each consisting of multiple layers, etc.

I am using Dev-C++, Allegro library, and Mappy to make the game.
I've put together a couple maps, and I can successfully put them into the textbook's example platform scroller's code, but I run into problems if the map is multiple layers. It will only show the lowest (0) layer.

My question probably has a pretty simple answer, but I'm having trouble figuring it out. I basically want to know how to enable the other layers of whatever map is loaded.

Any help or direction is greatly appreciated!

When you draw the tiles to the screen (or better yet, to a buffer which you later transfer all-at-once to the screen) using blit() or draw_sprite()?

I have never used mappy, so I can't provide any insight into its mechanism for handling layers. I would assume that it stores them in either a vector or an array.

If that's the case, simple iteration would do the trick:

for (layer = 0; layer < num_layers; ++layer)
{
  for (row = 0; row < screen_width; ++row)
  {
    for (col = 0; col < screen_height; ++col)
    {
      if (all_layers[layer].value > 0)
        draw_sprite(buffer, all_layers[layer].tilemap[all_layers[layer].value], col, row);
    }
  }
}

Of course, as Felix mentioned, it will help if you can tell us what you've done so far, even if you give us a few lines of your current drawing routines.

You are using two functions, MapDrawBG() and MapDrawFG() (lines 175 and 178). I assume that these functions give you your background (or a main background image with "tiles" in the foreground?).

Since I can't see what those functions are doing, I'm going to assume that the problem lies in the fact that you're not calling a function for each additional layer that needs to be drawn.

Within those functions, they probably point to the portion of data that was read in from your map2.fmp file, and converted into a tilemap. If that was loaded into only a single layer, and all the rest discarded, then you'll want to modify the MapLoad() function to load in for each desired layer.

If MapLoad() loads things in correctly, but you simply don't access the other layers (like I said earlier: because you don't have any other layer-drawing functions than MapDrawBG() and MapDrawFG() ), then you should create them.

That would be my guess at this point.

I am using Mappy to create the maps and Tile Studio to create the tiles for the maps.
They are both older programs, but I know that they can work accomplish what I need to accomplish.

The first map (map1.fmp) has 2 layers so far:
The background (layer 0) is the sky, clouds, etc.
The foreground (layer 1) is everything else so far...the ground, obstacles, etc.

When I try loading map1, it will show layer 0, the sky and clouds, but the foreground isn't showing.

I attached a couple files that are associated with this example program. They define a lot of things to get the mappy files to work with Allegro...but, being the newb that I am, I'm having trouble figuring out what I need to do...but I'm sure the answer is lying somewhere in those files.

Thanks for the insight so far!

edit - in the REDMEAL.TXT file, it goes over some things.
I see that for the MapDrawFG() on line 178, the only difference from MapDrawBF() on line 175 (which seems to be working) is that the last element passed is an int which specifies which layer to draw. I tried setting it to 1, which the foreground layer is for the map, but it still won't draw it when I run the program. :/

I used Mappy for the game Trashman. (It's not very good, don't feel obligated to look at it, but the source code is provided.)

Here is the drawing code I used:

MapChangeLayer(0);
MapDrawBG(buffer, camera.x, camera.y, 133, 79, (314-67)*2+3, (234-40)*2+3);

MapChangeLayer(1);
MapDrawFG(buffer, camera.x, camera.y, 133, 79, (314-67)*2+3, (234-40)*2+3, 0);

(This excerpt was taken from main.cpp in the source distribution.) The magic numbers should just be to place it in the game window. My map had two layers.