# How to get a hex terrain-based zoc propagation working? **URL:** \ **Category:** Module Design\ **Created:** [June 14, 2020, 4:47am UTC](https://forum.vassalengine.org/t/how-to-get-a-hex-terrain-based-zoc-propagation-working/10723 "2020-06-14T04:47:37Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Benkyo](https://forum.vassalengine.org/user_avatar/forum.vassalengine.org/benkyo/32/3289_2.png) [@Benkyo](https://forum.vassalengine.org/u/Benkyo)\ **Post date:** [June 14, 2020, 4:47am UTC](https://forum.vassalengine.org/t/how-to-get-a-hex-terrain-based-zoc-propagation-working/10723/1 "2020-06-14T04:47:37Z")
Here’s the situation: Hex grid, every hex already has a terrain-specific hex-shaped piece in it. Zone of control from a piece extends 2-3 hexes away from the piece, but only along some types of terrain - not water. To visualise this for the player, I’m trying to set up a command to view/clear the zoc. Something isn’t working, but I’m not sure what. The view zoc command is simply a GKC zoccomm with a fixed range of 1, looking for a property zoc==0 Each applicable terrain piece has the following traits from bottom up: DP zoc = 0, with a key command zocprop+1 to increment AoE with a range of 0 toggled by key zoc Trigger when zoc==0, triggers zoc, zocprop+1, zoccomm1 GKC activated by zoccomm1, sends zoctrig1 to property zoc==0 at range 1 Trigger when zoc==0, triggers zoc, zocprop+1, zoccomm2 GKC activated by zoccomm2, sends zoctrig2 to property zoc==0 at range 1 Trigger when zoc==0, triggers zoc This should(?) propagate the command 3 hexes along only the correct terrain, along lines of terrain that haven’t already been triggered, but nothing happens. Any tips? Ideas? ---
**Author:** ![Tim\_M](https://forum.vassalengine.org/user_avatar/forum.vassalengine.org/tim_m/32/2_2.png) [@Tim\_M](https://forum.vassalengine.org/u/Tim_M)\ **Post date:** [June 14, 2020, 5:24am UTC](https://forum.vassalengine.org/t/how-to-get-a-hex-terrain-based-zoc-propagation-working/10723/2 "2020-06-14T05:24:16Z")
I think your going to find a big headache here. I did hex specific pieces once - wasnt worth it. How do you control the formula? On what axis? Perhaps 2 are true but 4 are not (if you are using hexes…). It becomes very complex. How do you tell/ show this. Area of effect would be the one thing that comes to my mind as a visual display tool if it matches your formula criteria ---
**Author:** ![Benkyo](https://forum.vassalengine.org/user_avatar/forum.vassalengine.org/benkyo/32/3289_2.png) [@Benkyo](https://forum.vassalengine.org/u/Benkyo)\ **Post date:** [June 14, 2020, 5:42am UTC](https://forum.vassalengine.org/t/how-to-get-a-hex-terrain-based-zoc-propagation-working/10723/3 "2020-06-14T05:42:39Z")
All 6 axes, no control needed other than the fact that the blocking terrain has no triggers and is unaffected. ---
**Author:** ![Benkyo](https://forum.vassalengine.org/user_avatar/forum.vassalengine.org/benkyo/32/3289_2.png) [@Benkyo](https://forum.vassalengine.org/u/Benkyo)\ **Post date:** [June 15, 2020, 8:53pm UTC](https://forum.vassalengine.org/t/how-to-get-a-hex-terrain-based-zoc-propagation-working/10723/4 "2020-06-15T20:53:49Z")
OK, odd thing: I have kind of got this working, using exactly the traits I posted above, and it works better as 2 hexes than 3 (which is fine), but the command propagates in some odd inexplicable patterns. ![](https://i.ibb.co/jbTF0Hp/Antiquity-ZOC.png) Each of those red zones should extend from 2 hexes from the white-bordered pieces, excluding water, but _sometimes_ only extends one hex. The terrain is all from the same prototype and should function identically. Is there some command propagation limit going on? But if so, the tiny 3-hex zone on the bottom right makes no sense. Two other zones hemmed in by water worked fine, while all the other mostly open zones are missing hexes. I just can’t think of any way to explain this behaviour. ---
**Author:** ![Cattlesquat](https://forum.vassalengine.org/user_avatar/forum.vassalengine.org/cattlesquat/32/241_2.png) [@Cattlesquat](https://forum.vassalengine.org/u/Cattlesquat)\ **Post date:** [June 16, 2020, 3:09pm UTC](https://forum.vassalengine.org/t/how-to-get-a-hex-terrain-based-zoc-propagation-working/10723/5 "2020-06-16T15:09:15Z")
The algorithm you’ve roughly described “should work” in general terms. Which means that there’s probably something minor wrong in the details of your implementation, or how “range” is being calculated. ---
**Author:** ![Benkyo](https://forum.vassalengine.org/user_avatar/forum.vassalengine.org/benkyo/32/3289_2.png) [@Benkyo](https://forum.vassalengine.org/u/Benkyo)\ **Post date:** [June 16, 2020, 5:13pm UTC](https://forum.vassalengine.org/t/how-to-get-a-hex-terrain-based-zoc-propagation-working/10723/6 "2020-06-16T17:13:59Z")
…or there’s a bug in Vassal. There’s no way I can conceive of for the outcomes I screenshotted to all be possible. ---
**Author:** ![Cattlesquat](https://forum.vassalengine.org/user_avatar/forum.vassalengine.org/cattlesquat/32/241_2.png) [@Cattlesquat](https://forum.vassalengine.org/u/Cattlesquat)\ **Post date:** [June 16, 2020, 5:53pm UTC](https://forum.vassalengine.org/t/how-to-get-a-hex-terrain-based-zoc-propagation-working/10723/7 "2020-06-16T17:53:01Z")
Well, “no way I can conceive” is actually a pretty standard mental state in debugging code, right before the part where I actually find the bug. 😃 The best approach is probably to put in a whole lot of Report traits that show the “progress” of one of these – who thinks it’s sending a GCK, what GCK does it think it’s sending, who thinks it’s receiving a GCK, what does it think the state is when it receives it, etc, etc, etc. ---
**Author:** ![Benkyo](https://forum.vassalengine.org/user_avatar/forum.vassalengine.org/benkyo/32/3289_2.png) [@Benkyo](https://forum.vassalengine.org/u/Benkyo)\ **Post date:** [June 16, 2020, 8:00pm UTC](https://forum.vassalengine.org/t/how-to-get-a-hex-terrain-based-zoc-propagation-working/10723/8 "2020-06-16T20:00:47Z")
Oh, I think I have an answer. First GKC at range 1 Hex 1 at range 1 completes the trigger, does AoE, sends the second GKC, hexes at range 1 _from hex 1_ do AoE. Hex 2 at range 1 is one of the hexes already triggered by the second GKC above, so is no longer a valid target for the first GKC. This would explain most of the patterns above, and maybe even the tiny 3-hex result if the origin hex somehow triggered first. Thanks for the nudge. I’m too quick to assume Vassal is buggy. ---
**Author:** ![Benkyo](https://forum.vassalengine.org/user_avatar/forum.vassalengine.org/benkyo/32/3289_2.png) [@Benkyo](https://forum.vassalengine.org/u/Benkyo)\ **Post date:** [June 16, 2020, 8:54pm UTC](https://forum.vassalengine.org/t/how-to-get-a-hex-terrain-based-zoc-propagation-working/10723/9 "2020-06-16T20:54:02Z")
The solution is not to have conditions for the GKCs or triggers at all, and to not use zocprop as described. You do need a DP to prevent AoE from being turned off once it is on, but that’s all it is for. …now I can start work on the hard stuff.