Hi, I’m working in an isometric demo, up to now i got the projection working. I use this simple piece of code to get the job done

for(my=0; my< 30; my++ )
{
for(mx=0; mx< 30; mx++ )
{
sx=( mx * TILEM_W ) - ( my * TILEM_W );
sy=( my * TILEM_H ) + ( mx * TILEM_H );

masked_blit(tile,buffer,0,0,sx+SCREEN_W/2 -32 x,sy+cy,64,32);

}
}

As you can read the map is 30 x 30, tiles are 64 x 32.

The problem is how to draw only what is seen in a given moment and not drawing the entire map every time, so that drawing speeds up with bigger maps.

I’m still trying a couple of ideas I came up with but haven’t succeed.

Any one has an idea to help solve this isometric maddness?:-[

Don't draw diamond shaped maps.
It's way harder to draw them, way hareder to find the mouse position, etc.

Simply draw the map the way you'd draw a normal rectangular map. But: For every row increase y only by half the tileh eight and offset x every other row by half the tile width.

If you want diamond shaped levels, simply put only visible tiles there, and use transparen tiles around them.

Did this make sense?

You might want multiple layers.

I have multiple layers.
I draw the ground first
then any buildings/walls
then any roofs.

I draw the people sprites in the middle of drawing the walls. Draw all the that are farther away first. then draw the sprite. Then repeat for next sprite.

and about the diamond shapes maps. Now you tell me. Oops. Because of the order of drawing, that is why I have a diamond shaped drawing

      0
    1   2
  3   4   5
6   7   8   9
  A   B   C
    D   E
      F

And it was hard to draw it. That's when I came up with the template system. I calculated the position for each tile before hand. Then all I had to do to draw it was draw the tiles

draw_map()
for int i = 0 to MAXTILES i++
template.draw(i);

There are too many calculations done in the map drawing. By doing all the calculations once in the template there are very little left during drawing. So far I get 80+ FPS.

Draw the map like this:

   0 1 2 3 4
    5 6 7 8 9
   a b c d e

Now imagine that the lines are half the tile height apart... like this:
http://www.steinke.net/download/iso.gif

See? That way you can use a slightly altered rect map drawing algorithm.

Spellcaster:

I got the isometric stuff working with non diamond shaped maps, think its a better way to go, thanks for the advice.8-)

I'm dumb!... spellcaster shouldn't u know better...

use the diamond-style, but use it different...
(another way of drawing(really better for looping/wrapping tiles))

sorry I give u the dignity to commup with the anwser...(it is much better than that odd/even stuff) so that were all the hints...

[url http://home.wanadoo.nl/~mkmk/screen2%20copy.jpg]
ps... sorry the new engine is ready soon...(so new screenshots)

gay... but I now own u(if it is something new to you).. well I now own all the people who read it:

so bow for me, I am the elite...(still searching for others)

well enough about that;D

      0
    1   3
  2   4   6 
    5   7
      8

this is simpler isn't it... well it has more...

I never need to worry about odd/even... so e.g. circles will be circles...8-)

the algoritm to place the tiles(so that they overlap the good way) is fairly difficult in the other diamond way.
In my way it is really straight forward...

and about the circles... in my way it is really easy to change diameter without a set of precalculated masks(U use that... I think?).

I think u should relook the numbers...;)
(cya tomorrow(need to sleep))

d00d, why did you not propose the "normal" way... Cos DanielH proposed:

      0
    1   2
  3   4   5
6   7   8   9
  A   B   C
    D   E
      F

which is totally sick...
and u only proposed the odd/even way...
So I thought why doesn't anybody propose the way I use...(yes your normal way is abvious totally the same(so yes we were talking about no problem))

But I still think that the "normal" way is better than the zigzaw way. take for instance the calculation of a guy on ht isometric tile-map... in the jigzaw-way u still need to worry about odd/even... and also for placement that is neccesary... as for the normal way... all is pretty straight forward...

My map is like this

      0
    4   1
  8   5   2
C   9   6   3
  D   A   7
    E   B
      F

but I draw it in this order. That was a problem.

      0
    1   2
  3   4   5
6   7   8   9
  A   B   C
    D   E
      F

By determining which tiles go where and when, the drawing was easy. All I have to do is supply which tile is at pos 0. Then the map template program does all the work. Very easy very quick.

I have varying size tiles, width and height. So I also check to see if any are inside the drawing area before trying to draw them. That saves time also.

About the tiles, the bases are all the same. 64x32, but you can have anysize object. Just center it vertically in the tile and adjust it so that the bottom of the object is in the center of the tile.

d00ds... think....So I was right, u people don't get it(well at least danielH)...

The drawing order IS:

      0
    4   1
  8   5   2
C   9   6   3
  D   A   7
    E   B
      F

And just for the info... my tile-map=3000*3000 tiles(32*32 bitmaps see my screenshot), and it is wrapped(looping)
and to spellcaster:
the "guy" has a real xy, a screen xy and a tile xy which is simply calculated from the other two.