Map Analysis

Discussion in 'Civ2 - Strategy & Tips' started by Ali Ardavan, Nov 2, 2006.

1. Ali ArdavanMathematicianModeratorCiv2 GOTM Staff

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Definition:
Map Analysis allows you to decipher more about the map you are playing on than is readily visible.
It requires the use of the standard Map Editor that shipped with Civ2.
It does not require black-clicking.

Usefulness:
It allows you to know where the huts are so you can get to them more quickly when hut hunting (black-clicking can make this even more powerful by letting you know which locations are not on land).
It also allows you to know which grasslands are on a special. This latter info is very precious for any (future) large/productive city but crucially so for your science city.

Map Editor facts

1. Coordinates (x,y) in Map Editor correspond to
Coordinates (2x,y) in Civ2 if y is even and to
Coordinates (2x+1,y) in Civ2 if y is odd

2. The location of huts, location of resources, and type of resources (whale versus fish) are controlled by a single parameter called Resource Seed which can be set from the Map Editor.

3. While the resource seed range is huge, there are only 64 unique possibilities. That is, the map for resource seed x is identical to the map for x+64

4. Let y=x+32. The only difference between a map whose resource seed is y and a map whose resource seed is x is the type of the resources. The locations of the resources and huts are identical.

5. Let y=x+16. The only difference between a map whose resource seed is y and a map whose resource seed is x is the type of the resources and the location of huts. The locations of the resources are identical.

6. Unlike all other terrain types which come in 3 types (unspecial, fish special, whale special), Grassland comes in 2 types (shielded or unshilded). The shields have their own pattern which is totally independent of the special resources pattern. While I can describe the pattern, it is so easy to see that you may as well just create a big land mass of all grassland in Map Editor and see it for yourself.

(7 & 8 below are postscript. Thank you ElephantU and SlowThinker.)

7. The pattern of the specials is always the same regardless of the seed. That is, the relative locations of specials (ignoring the type of the special) to one another is always the same.

8. There are 4 groups of seeds: 0-15, 16-31, 32-47, 48-63. If you change the seed within a group the pattern of the specials is only shifted. The relative location and types of the specials remain the same. In other words, if you ignore the coordinates the pattern does not change within a group of 16. See the posts by ElephantU and SlowThinker below for pictures and detailed description of these patterns.

How to do Map Analysis for a fresh Civ2 game

Siwtch to view mode. Take the cursor around to figure out the highest x and y coordinates you can find. Also find out whether the map is round or flat. Start the Map Editor. Create a blank map whose width is (x+1)/2 and whose height is (y+1). Use fact 1 above to find the tile in the Map Editor that corresponds to your starting location. Draw in the visible land. The resource seed always starts at 1; increment it till you get any visible specials in the right locations. At this step you are ignoring the special's type. That is, if you get fish where you expect whale it is OK. Just get the locations right. Once this is done if the special types or the visible huts are not right, use rules 4 and 5 above to make them right.

If you have few visible specials or huts you may not find a uinque resource seed. Often this happens when there is plenty of grassland at the starting loction. Map Analysis is still useful though as it may tell you where to go nearby to resolve the ambiguity.

Once you figure out the resource seed you know the location of all the specials (even if covered by grassland) and huts.

Useful Civ2 Map facts

1. If resource seed of a custom map is 1, Civ2 chooses another resource seed randomly. For all other resource seeds Civ2 asks you in the start up sequence whether you want the resource seed randomized. Thus, if you have designed a map and want to keep its resource seed at 1 use 65 instead.

2. Whales and Fish that are not accessible from a potential city located anywhere are not shown in Civ2. Thus if you are exploring and see a whale or a fish next to darkness land is close by.

3. Grassland is the only land type that hides special resources. The best way to reveal the resource is to mine the grassland into forest.

4. If the map is round, tiles whose x coordinate are close enough to zero to be within the radius of two cities located on the opposite sides of the x=0 line can be simultaneously used by both cities.

2. Bloody BenChieftain

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omg. x? y? mathematical equations? playing civ2 just gets more and more complicated...

3. ElephantUDeity

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You should see Samson's City Supply/Demand formulas...

One trick of mine is when drawing my reference map in MapEditor I use Tundra or Glacier to "stand in" for Grass, since this lets me see the hidden specials underneath while I am searching through the Resource Seeds. Once I lock it in (and sometimes I have to play a few turns to reveal extra specials or huts to confirm) I'll convert them back to Grass except for those that have something hidden underneath.

Might be nice if you also said something about the four different special patterns and how to recognize them.

4. PeasterEmperor

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You can get the same info from a utility, such as hutfinder or civ2admin. I haven't tried it with the Map Editor, and I don't know which way is easier (or more fun). Can anybody compare these two methods?

5. Ali ArdavanMathematicianModeratorCiv2 GOTM Staff

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I use the same tactic. I use glacier for grass exactly as you said. I use Tundra for unexplored, that way I can tell where the known oceans are. The latter is useful when I am using black-clicking in conjunction with Map Analysis to map out my the vicinity of my starting location for hut hunting and future city placement.
I am not sure what you are referring to. If you mean the difference between seeds x, x+16, x+32, and x+48 I already have.

6. ElephantUDeity

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No, I meant the four different patterns that appear. Let me illustrate with some pictures. In each picture I have circled the "center" of each group of eight specials; there is always a row of four specials spaced three tiles along a diagonal "row" and one tile to the side, with two "outrigger" specials on each side of the center row

This picture shows the pattern for the first set of seeds, from #1 to #15. Each horizontal band is composed of all the same special, and the bands alternate.

This picture shows the pattern for the second band of specials, from seed #16 to #31. The four specials through the center of the group of eight (circled) are all the same types; the "outriggers" are all the opposite types. Each band vertically switches the type of center and outriggers.

This picture is the third set of specials, for seeds from #32 to #47. The center row of specials alternate type, and the outriggers are the opposite type of the center they line up with. As before, the bands alternate direction of the center row, but the "bottom" special will always be of the same type.

This picture is the fourth set of specials, from seeds #48 to #63. In this group one of the center rows of the two bands will have two of one special followed by two of the other special (here the upper); the other band with have the two in the middle of the center row the same and the two at the ends the other special (the lower). In the first, upper band the outriggers are of different types, such that one set will make a three-pointed star (here the whales). In the second, lower band the outriggers are of the same type, so there will be a box of four of the same type (here the fish) with four others "wrapped around" the box half-way. Discovering the box of four can lead you to think you have a seed in the #1-15 group, but finding the rest of the set will show that they are of the opposite type.

7. SlowThinkerPrince

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It should be explained how the 4 groups are defined:
For example the attached image represents seed group 2 (from #16 to #31). On the picture Plains squares are fish type and Swamp squares are whales type. You can see the layout is tessellated. For group 2 size of a chessboard tile is 2x2. (For group 1 it is 1x1, for group 2 it is 2x2, for group 3 it is 4x4, for group 4 it is 8x8.)

Here I included the chessboard in one of Elephant's pictures (group 4, so chessboard tiles are 8x8):

Mathematical description is in the samson's thread: Location of Huts

8. MercatorEmperor

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Are you so forgetful that you can't remember what size and shape map you started your game with? Even GOTMs have their shape and size mentioned already anyway.

9. Ali ArdavanMathematicianModeratorCiv2 GOTM Staff

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Now here is a question for both you and SlowThinker who elaborated further on your response:
How do I use the information you just described?

10. Ali ArdavanMathematicianModeratorCiv2 GOTM Staff

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Good point. This step is only necessary if the map is created by someone else.
True and on 1-2 occasions the posted dimensions/shape were incorrect.

11. SlowThinkerPrince

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There are two strong statements in Elephant's and my pictures, but maybe they are not stressed adequately (and you should probably add them to the first post):

There are 4 groups of seeds, 0-15, 16-31, 32-47, 48-63.
Elephant is saying there is only 1 pattern among all 16 seeds of one group, and the only difference among these 16 seeds is that this pattern is shifted.
I didn't express it clearly, but the placement of chessboard tiles is identical among seeds of one group. In other words it is NOT shifted in relation to coordinates. So you can easily count a type of special from coordinates (provided you know the seed group and so a size of a chessboard tile).

Of course you don't have to use this information if you use Hutfinder or Civ2Admin.
Without these tools and with knowledge of patterns shown by Elephant you need to identify only a part of the pattern in your game and you know placement of all specials (and huts; Elephant omitted them).
And with use of samson's math you can localize the pattern even quicker
(from coordinates of ONE special you can identify the seed number, except you don't know the group exactly, so there are 4 possibilities x, x+16, x+32, x+48 (knowledge of special type can eliminate some);
from coordinates of ONE hut you can identify the seed number too, except you don't know the group, and there are 2 possibilities x, x+32)
(IMO this is another strong statement that deserves to be in the summary in the 1st post)

12. SlowThinkerPrince

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I edited my post with pictures.

13. Ali ArdavanMathematicianModeratorCiv2 GOTM Staff

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Thank you SlowThinker for futher clarification. I have added the following to the first post under Map Editor facts.

7. The pattern of the specials is always the same regardless of the seed. That is, the relative locations of specials (ignoring the type of the special) to one another is always the same.

8. There are 4 groups of seeds: 0-15, 16-31, 32-47, 48-63. If you change the seed within a group the pattern of the specials is only shifted. The relative location and types of the specials remain the same. In other words, if you ignore the coordinates the pattern does not change within a group of 16. See the posts by ElephantU and SlowThinker below for pictures and detailed description of these patterns.

14. Ali ArdavanMathematicianModeratorCiv2 GOTM Staff

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Thank you ElephantU for pointing out the general pattern (response #6). I just used it in GOTM70 where the map is too big to recreate in the map editor.