Drawing Isometric game worlds

Question

What is the correct way to draw isometric tiles in a 2D game?

I've read references (such as this one) that suggest the tiles be rendered in a way that will zig-zag each column in the 2D array representation of the map. I imagine that they should be drawn more in a diamond fashion, where what gets drawn to the screen relates more closely to what the 2D array would look like, just rotated a little.

Are there advantages or disadvantages to either method?

User · Answer

You could use euclidean distance from the point highest and nearest the viewer  except that is not quite right  It results in spherical sort order  You can straighten that out by looking from further away  Further away the curvature becomes flattened out  So just add say 1000 to each of the x y and z components to give x  y  and z   The sort on x  x  y  y  z  z

User · Answer

Coobird s answer is the correct  complete one   However  I combined his hints with those from another site to create code that works in my app  iOS Objective-C   which I wanted to share with anyone who comes here looking for such a thing   Please  if you like up-vote this answer  do the same for the originals  all I did was  stand on the shoulders of giants    As for sort-order  my technique is a modified painter s algorithm  each object has  a  an altitude of the base  I call  level   and  b  an X Y for the  base  or  foot  of the image  examples  avatar s base is at his feet  tree s base is at it s roots  airplane s base is center-image  etc    Then I just sort lowest to highest level  then lowest  highest on-screen  to highest base-Y  then lowest  left-most  to highest base-X   This renders the tiles the way one would expect   Code to convert screen  point  to tile  cell  and back   typedef struct ASIntCell       like CGPoint  but with int-s vice float-s     int x      int y    ASIntCell      Cell-math helper here          http   gamedevelopment tutsplus com tutorials creating-isometric-worlds-a-primer-for-game-developers--gamedev-6511    Although we had to rotate the coordinates because       X increases NE  not SE     Y increases SE  not SW     ASIntCell  cellForPoint   CGPoint  point       const float halfHeight   rfcRowHeight   2        ASIntCell cell      cell x     point x   rfcColWidth  -   point y - halfHeight    rfcRowHeight        cell y     point x   rfcColWidth      point y   halfHeight    rfcRowHeight         return cell         Cell-math helper here          http   stackoverflow com questions 892811 drawing-isometric-game-worlds 893063    X increases NE     Y increases SE    CGPoint  centerForCell   ASIntCell  cell       CGPoint result       result x    cell x   rfcColWidth    2     cell y   rfcColWidth    2       result y    cell y   rfcRowHeight   2  -  cell x   rfcRowHeight   2        return result

User · Answer

If you have some tiles that exceed the bounds of your diamond   I recommend drawing in depth order      1      234    56789    abc      d

User · Answer

Real problem is when you need draw some tile/sprites intersecting/spanning two or more other tiles.

After 2 (hard) months of personal analisys of problem I finally found and implemented a "correct render drawing" for my new cocos2d-js game. Solution consists in mapping, for each tile (susceptible), which sprites are "front, back, top and behind". Once doing that you can draw them following a "recursive logic".

User · Answer

Either way gets the job done  I assume that by zigzag you mean something like this   numbers are order of rendering           01               06  02         11  07  03       16  12  08  04 21  17  13  09  05   22  18  14  10     23  19  15           24  20             25           And by diamond you mean                        01  02  03  04     05  06  07       08  09  10  11     12  13  14       15  16  17  18     19  20  21       22  23  24  25                      The first method needs more tiles rendered so that the full screen is drawn  but you can easily make a boundary check and skip any tiles fully off-screen  Both methods will require some number crunching to find out what is the location of tile 01  In the end  both methods are roughly equal in terms of math required for a certain level of efficiency

User · Answer

Update  Corrected map rendering algorithm  added more illustrations  changed formating   Perhaps the advantage for the  zig-zag  technique for mapping the tiles to the screen can be said that the tile s x and y coordinates are on the vertical and horizontal axes    Drawing in a diamond  approach   By drawing an isometric map using  drawing in a diamond   which I believe refers to just rendering the map by using a nested for-loop over the two-dimensional array  such as this example   tile map                    for  cellY   0  cellY  lt  tile map size  cellY         for  cellX   0  cellX  lt  tile map cellY  size cellX             draw              tile map cellX  cellY               screenX    cellX   tile width    2     cellY   tile width    2              screenY    cellY   tile height   2  -  cellX   tile height   2              Advantage   The advantage to the approach is that it is a simple nested for-loop with fairly straight forward logic that works consistently throughout all tiles   Disadvantage   One downside to that approach is that the x and y coordinates of the tiles on the map will increase in diagonal lines  which might make it more difficult to visually map the location on the screen to the map represented as an array     However  there is going to be a pitfall to implementing the above example code -- the rendering order will cause tiles that are supposed to be behind certain tiles to be drawn on top of the tiles in front     In order to amend this problem  the inner for-loop s order must be reversed -- starting from the highest value  and rendering toward the lower value   tile map                    for  i   0  i  lt  tile map size  i         for  j   tile map i  size  j  gt   0  j--       Changed loop condition here          draw              tile map i  j               x    j   tile width   2     i   tile width   2              y    i   tile height   2  -  j   tile height   2              With the above fix  the rendering of the map should be corrected      Zig-zag  approach   Advantage   Perhaps the advantage of the  zig-zag  approach is that the rendered map may appear to be a little more vertically compact than the  diamond  approach     Disadvantage   From trying to implement the zig-zag technique  the disadvantage may be that it is a little bit harder to write the rendering code because it cannot be written as simple as a nested for-loop over each element in an array   tile map                    for  i   0  i  lt  tile map size  i         if i is odd          offset x   tile width   2     else          offset x   0      for  j   0  j  lt  tile map i  size  j             draw              tile map i  j               x    j   tile width    offset x              y   i   tile height   2             Also  it may be a little bit difficult to try to figure out the coordinate of a tile due to the staggered nature of the rendering order     Note  The illustrations included in this answer were created with a Java implementation of the tile rendering code presented  with the following int array as the map   tileMap   new int            0  1  2  3        3  2  1  0        0  0  1  1        2  2  3  3       The tile images are    tileImage 0  - gt  A box with a box inside  tileImage 1  - gt  A black box  tileImage 2  - gt  A white box  tileImage 3  - gt  A box with a tall gray object in it    A Note on Tile Widths and Heights  The variables tile width and tile height which are used in the above code examples refer to the width and height of the ground tile in the image representing the tile     Using the dimensions of the image will work  as long as the image dimensions and the tile dimensions match  Otherwise  the tile map could be rendered with gaps between the tiles

[2d] Drawing Isometric game worlds

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