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Define basic neighborhood functions for 2D Grids. The basic interface defines a width and a height (not all grids require a width and a height unless you're doing toroidal grids), and basic math for toroidal computation, hex grid location, and triangular grid location.
If you're using the Grid to define a toroidal (wrap-around) world, you can use the tx and ty methods to simplify the math for you. For example, to increment in the x direction, including wrap-around, you can do: x = tx(x+1).
If you're sure that the values you'd pass into the toroidal functions would not wander off more than a grid dimension in either direction (height, width), you can use the slightly faster toroidal functions stx and sty instead. For example, to increment in the x direction, including wrap-around, you can do: x = stx(x+1). See the documentation on these functions for when they're appropriate to use. Under most common situations, they're okay.
In HotSpot 1.4.1, stx, and sty are inlined. In Hotspot 1.3.1, they are not (they contain if-statements).
(0,0) (2,0) (4,0) (6,0) ... (1,0) (3,0) (5,0) (7,0) ... (0,1) (2,1) (4,1) (6,1) ... (1,1) (3,1) (5,1) (7,1) ... (0,2) (2,2) (4,2) (6,2) ... (1,2) (3,2) (5,2) (7,2) ... ... ... ... ... ... ... ... ... ... ...
The rules moving from a hex location (at CENTER) to another one are as follows:
UP x UPLEFT y - 1 UPRIGHT x - 1 x + 1 ((x % 2) == 0) ? y - 1 : y CENTER ((x % 2) == 0) ? y - 1 : y x DOWNLEFT y DOWNRIGHT x - 1 x + 1 ((x % 2) == 0) ? y : y + 1 DOWN ((x % 2) == 0) ? y : y + 1 x y + 1NOTE: (x % 2 == 0), that is, "x is even", may be written instead in this faster way: ((x & 1) == 0)
Because the math is a little hairy, we've provided the math for the UPLEFT, UPRIGHT, DOWNLEFT, and DOWNRIGHT directions for you. For example, the UPLEFT location from [x,y] is at [ulx(x,y) , uly(x,y)]. Additionally, the toroidal methods can be used in conjunction with the hex methods to implement a toroidal hex grid. Be sure to To use a toroidal hex grid properly, you must ensure that height of the grid is an even number. For example, the toroidal UPLEFT X location is at tx(ulx(x,y)) and the UPLEFT Y location is at ty(uly(x,y)). Similarly, you can use stx and sty.
While this interface defines various methods common to many grids, you should endeavor not to call these grids casted into this interface: it's slow. If you call the grids' methods directly by their class, their methods are almost certain to be inlined into your code, which is very fast.
------------------------- \(0,0)/ \(0,2)/ \(0,4)/ \ \ / \ / \ / \ ... \ /(0,1)\ /(0,3)\ /(0,5)\ ------------------------- / \(1,1)/ \(1,3)/ \(1,5)/ / \ / \ / \ / ... /(1,0)\ /(1,2)\ /(1,4)\ / ------------------------- \(2,0)/ \(2,2)/ \(2,4)/ \ \ / \ / \ / \ ... \ /(2,1)\ /(2,3)\ /(2,5)\ ------------------------- / \(3,1)/ \(3,3)/ \(3,5)/ / \ / \ / \ / ... /(3,0)\ /(3,2)\ /(3,4)\ / ------------------------- . . .
How do you get around such a beast? Piece of cake! Well, to go to your right or left neighbor, you just add or subtract the X value. To go to your up or down neighbor, all you do is add or subtract the Y value. All you need to know is if your triangle has an edge on the top (so you can go up) or an edge on the bottom (so you can go down). The functions TRB (triangle with horizontal edge on 'bottom') and TRT (triangle with horizontal edge on 'top') will tell you this.
Like the others, the triangular grid can also be used in toroidal fashion, and the toroidal functions should work properly with it. To use a toroidal triangular grid, you should ensure that your grid's length and width are both even numbers.
We'll provide a distance-measure function for triangular grids just as soon as we figure out what the heck one looks like. :-)
Method Summary | |
int |
dlx(int x,
int y)
Hex downleft x. |
int |
dly(int x,
int y)
Hex downleft y. |
int |
downx(int x,
int y)
Hex down x. |
int |
downy(int x,
int y)
Hex down y. |
int |
drx(int x,
int y)
Hex downright x. |
int |
dry(int x,
int y)
Hex downright y. |
int |
getHeight()
Get the height |
void |
getNeighborsHamiltonianDistance(int x,
int y,
int dist,
boolean toroidal,
IntBag xPos,
IntBag yPos)
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void |
getNeighborsHexagonalDistance(int x,
int y,
int dist,
boolean toroidal,
IntBag xPos,
IntBag yPos)
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void |
getNeighborsMaxDistance(int x,
int y,
int dist,
boolean toroidal,
IntBag xPos,
IntBag yPos)
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int |
getWidth()
Get the width |
int |
stx(int x)
Simple [and fast] toroidal x. |
int |
sty(int y)
Simple [and fast] toroidal y. |
boolean |
trb(int x,
int y)
Horizontal edge is on the bottom for triangle. |
boolean |
trt(int x,
int y)
Horizontal edge is on the top for triangle. |
int |
tx(int x)
Toroidal x. |
int |
ty(int y)
Toroidal y. |
int |
ulx(int x,
int y)
Hex upleft x. |
int |
uly(int x,
int y)
Hex upleft y. |
int |
upx(int x,
int y)
Hex up x. |
int |
upy(int x,
int y)
Hex up y. |
int |
urx(int x,
int y)
Hex upright x. |
int |
ury(int x,
int y)
Hex upright y. |
Method Detail |
public int getWidth()
public int getHeight()
public int tx(int x)
public int ty(int y)
public int stx(int x)
public int sty(int y)
public int ulx(int x, int y)
public int uly(int x, int y)
public int urx(int x, int y)
public int ury(int x, int y)
public int dlx(int x, int y)
public int dly(int x, int y)
public int drx(int x, int y)
public int dry(int x, int y)
public int upx(int x, int y)
public int upy(int x, int y)
public int downx(int x, int y)
public int downy(int x, int y)
public boolean trb(int x, int y)
public boolean trt(int x, int y)
public void getNeighborsMaxDistance(int x, int y, int dist, boolean toroidal, IntBag xPos, IntBag yPos)
public void getNeighborsHamiltonianDistance(int x, int y, int dist, boolean toroidal, IntBag xPos, IntBag yPos)
public void getNeighborsHexagonalDistance(int x, int y, int dist, boolean toroidal, IntBag xPos, IntBag yPos)
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