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Tile based map. Part 2.

Tile based map.

by Vladimir Vasilyev

 Part2.

Introduction.

  The basic idea used at construction of a map is next :
We admit (allow), that the map is already correctly constructed so it is necessary only to replace in the chosen cell of a map one type of a surface with another.
     
Actually, on this place the second part of the paper can be completed, since further it is necessary only accurately to consider all special cases of such replacement. As an example, we shall consider one of variants.

Drawing by the HI type on the LOW. (Hi to Low)

    For the beginning we shall consider a case, when a new and old type of a surface belong to one set and the new type of a surface is the HI type. In a considered example an old type of a surface - GROUND new - a GRASS and both types belong to the same TILESET2: GROUND - GRASS and GRASS is the HI type in relation to GROUND. (according to accepted in the first part of clause to designations and names).  

Fig. 1 Fig. 2 Fig. 3

For such type of the replacement, for the tile, selected on fig1 - we shall name it further as central - it is required in addition to replace only eight its nearest neighbors. The distant neighbors do not changed in this case.

The process of calculation of new bit representations for the nearest neighbors consists of two stages and is realized in the editor in procedure DoMain1x1.

At the first stage the bit representation for everyone tile sets to nil and then known (in the sense that for these bits is precisely known its meaning ) bits are set to the necessary value. For new central tile bit representation is  1111111. As the nearest neighbors on borders should be coordinated with central tile that we shall receive the following known meanings of bits.

Number  of the neighbour

Bit masks

Fig. 4

Hi bit - top
7654

Low bit - party
3210

0

0110

0100

1

1100

1000

2

1001

0001

3

0011

0010

4

0100

0000

5

1000

0000

6

0001

0000

7

0010

0000

The values of  bit masks are stored in MaskArr1.  

  FTileMap [ny, nx] .SetN: = AMapBrush; // i.e. = cSetN;

TileBits: = 0; // is cleared all bits
TileBits: = TileBits or MaskArr1 [i]; // drawing by Bit=1

It is possible to tell, that in this case (Hi to Low) we " draw by bit 1 ".

At the second stage it is necessary to receive missing meanings of bits. For this purpose we pass on the just calculated nearest neighbors again and for each of them we spend procedure of the coordination (in the editor it is procedure CheckNeighbours (nx, ny)) sides and tops for current tile with already its nearest neighbors.

Fig. 5   

 

If we draw by a LOW type on the HI from one TILESET, it is necessary, accordingly,   " to draw by zero ":

  if AMapBrush-SetN =-1 then
begin
 TileBits:=FTileMap[ny,nx].TileBits;//get the value
  // combine it with the mask - drawing by Bit=0
 
TileBits: = TileBits and MaskArr0 [i];
end;

 

If a new and old type of a surface belong to different sets, we reduce (increase) number of a brush and draw the central cell and nearest neighbors by intermediate terrain types. (in the editor it is procedure Do1x1 (cnx, cny: Longint; const AMapBrush: byte)

The procedure corrects a MapBrush and recursive calls itself while we shall not receive the case described in the beginning of the clause, then the execution passes to procedure DoMain1x1 (cnx, cny, AMapBrush);

I have increased amount of the comments in a code of the editor and I hope, that you can understand all ideas. If it is not  - write to me and I shall tell about difficult places, from your point of view, in more detail.

Copyright    2001   Vladimir Vasilyev.  
Any part of given clause, including illustrations, in any purposes can not be reproduced in any form and any means without the written permission  of the author.

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