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-   -   Targetting and LOS discussion wiki page (http://angband.oook.cz/forum/showthread.php?t=2046)

RogerN June 25, 2009 19:35

Regarding the section "Diamond walls, point visibility". A possible disadvantage is that, for certain arrangements of pillars, you can end up with disconnected regions of visibility (i.e. a dotted line of visible tiles which do not touch):

Code:

@#?????
...
###.#
    .
    ?.?

        ?.?


PaulBlay June 25, 2009 19:38

Quote:

Originally Posted by RogerN (Post 21162)
Code:

@#?????
...
###.#
    .
    ?.?

        ?.?


I think that's worth adding to the wiki. I think I'll do up a larger scale diagram to double check (not that I doubt you, but to make it easier to visualize).

RogerN June 25, 2009 19:47

Quote:

Regarding the section "Diamond walls, point visibility". A possible disadvantage is that, for certain arrangements of pillars, you can end up with disconnected regions of visibility (i.e. a dotted line of visible tiles which do not touch)
Incidentally, these artifacts are the result of allowing line-of-sight to pass through tiles which aren't visible. In other words, a line going to the center of tile A is obstructed by some other intervening wall, making tile A invisible. But a line which passes through the corner of tile A is allowed to go through (since it doesn't intersect the diamond), and therefore you may end up with disconnected visible tiles on the far side of tile A.

PaulBlay June 25, 2009 20:01

1 Attachment(s)
OK, here's my version of your fig.

Green diamonds = visible walls
Red diamonds = out-of-LOS walls
Dots = visible floor tiles

There's a big version at the wiki page. (A bit too big really ;-)

buzzkill June 25, 2009 20:47

Quote:

Originally Posted by PaulBlay (Post 21168)
OK, here's my version of your fig.

Green diamonds = visible walls
Red diamonds = out-of-LOS walls
Dots = visible floor tiles

There's a big version at the wiki page. (A bit too big really ;-)

I'll take issue with that. The 2 southernmost dots, are not visible. The furthest dot is a borderline case, normally visible, but since it is borderline blocked from 2 opposing sides, is has to be considered non-visible (even if a special exception be made). The dot above it has no line of sight to the center point.

RogerN June 25, 2009 20:59

Quote:

The 2 southernmost dots, are not visible. The furthest dot is a borderline case, normally visible, but since it is borderline blocked from 2 opposing sides, is has to be considered non-visible (even if a special exception be made). The dot above it has no line of sight to the center point.
Paul's diagram is not exactly the same as mine. In my diagram, the two southernmost points are 1 tile farther to the right. In the situation as I originally described it, both points clearly have LOS to the center and neither case is borderline.

Diagram to follow...

PaulBlay June 25, 2009 21:02

Quote:

Originally Posted by buzzkill (Post 21172)
I'll take issue with that. The 2 southernmost dots, are not visible. The furthest dot is a borderline case, normally visible, but since it is borderline blocked from 2 opposing sides, is has to be considered non-visible (even if a special exception be made). The dot above it has no line of sight to the center point.

This isn't the Digital Field of View method, there is nothing stated in the definition to disallow a LOV just because it touches exactly the point of a wall tile above in one place and below in another.

You're probably right about the dot in the middle, although it should be noted that my diagram is not 100% accurate and should be checked with maths before being taken as gospel.

Code:

@#?????
...
###.#
    .
    ? ?

        ?.?

Probably the middle dot shouldn't be there - as shown above.

PaulBlay June 25, 2009 21:13

Quote:

Originally Posted by RogerN (Post 21173)
Paul's diagram is not exactly the same as mine.

Yeah, it's a lot easier to see when you replace the spaces with x's.

Code:

@#?????xxxx
...xxxxxxxx
###.#xxxxxx
xxxx.xxxxxx
xxxxx?.?xxx
xxxxxxxxxxx
xxxxxxxx?.?

I'll put up a mark two.

RogerN June 25, 2009 21:15

This is the correct diagram. You can see that the two southernmost points are not borderline (although they are close to borderline); they are clearly visible according to the rules.

http://mysite.verizon.net/rogercnorris/los.png

PaulBlay June 25, 2009 21:19

Quote:

Originally Posted by RogerN (Post 21178)
This is the correct diagram. You can see that the two southernmost points are not borderline

The third of the horizontal trio is borderline, though. I think it 'just' touches the diamond, so it's safe under the definitions used.


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