LOS question on RB VASL board into a Gully

[Simon62]

Hi

I have a question on LOS when using the LOS tools on the RB map - I could well be that this is my mis-understanding of the LOS rules in which case I am hoping that VASL is correct and it is I that are wrong.

I have a unit in the 1st floor of building RB AA22 and it is checking LOS into the gully hexes RB EE24 & RB FF24.

LOS to RB EE24 is blocked I think due to rule A6.3 depressions as the hight difference of the sighting unit is less than the range between the unit and RB EE24.

LOS to RB FF24 however is clear according to VASL - I am confused with this one, the example in A6.3 indicates that once you have a LOS into a depression then as long as the LOS stays within the gully artwork then subsequent gully hexes are also in LOS. However, RB EE24 is showing as no LOS so I cannot see how FF24 could be in LOS as it should abide by the main A6.3 rule and the height advantage of the unit looking is not greater than the distance to the gully hex, it cannot see into EE24 and thus it can't run a LOS through the Gully from EE24 to FF24. If EE24 was in LOS then I think FF24 would also be in LOS

I am sure that it is me that is wrong on this but can't see my mistake - could anyone help me out?

Regards

Simon

 

[Simon62]

By the way I am using VASL 6.6.4 and VASSAL 3.6.6 and the latest R boards

 

[Robin Reeve]

Could you provide an image?
It would help us answer you without having to go and find the mapboard.

 

[Simon62]

Hope this helps 1 pic shows blocked LOS to RB EE24 and one an open LOS to RB FF24 - I think they should both be blocked, however, as mentioned I maybe wrong and they are both valid if so can you explain why

Regards

Simon

 

[Robin Reeve]

A22 can only see EE24 if at level 3 (which does not exist), as per normal LOS rules. The rubble in CC23 plays no role.
See A6.3 DEPRESSIONS :

A unit must be at least one level higher for every hex of range to units IN a Depression to have a LOS to them

A22 is at 3 hexes from EE24, so it only must be at 4 levels higher than the IN hex level of EE24 to have LOS into it.

 

[Simon62]

Ok that’s what I think but why does VASL think there is a LOS to fF24?

 

[apbills]

LOS into depressions is often misunderstood, I am a culprit. I think it is due to not having a good example. You must have sufficient elevation advantage (per A6.3) to see INTO the first depression hex in order to see into any of the same level depressions that may extend further away. The exception in A6.3 "[EXC: Units with a clear LOS between them through other continuous Depression hexsides (exclusive of vertices) need not count those intervening Depression hexes in determining the necessary elevation advantage]. " is a bit tricky, in your LOS case, it means you could ignore hex EE24 in determining the elevation needed to see INTO FF24. That means in order to see INTO FF24 you would need to have the same elevation advantage as you would need to see INTO EE24. The range to EE24 is 4 hexes, the elevation of EE24 is -1 (actually 0, but we will normalize the brown level as level 0), so you would need to be 4 levels higher in AA22 (level 3). The exception means that even though the range to FF24 is 5, you can ignore EE24 as part of the range if you could actually see INTO EE24 - allowing a unit in AA22 level 3 to see INTO FF24 even though the actual range is 5 (which normally would require the unit to be on level 4 in AA22).

Many people play LOS into depressions similar to hills, and assume that because the LOS crosses a depression hexside, there is a blind hex in EE24, but FF24 is clear. This is incorrect. Bottom line is that the VASL LOS file for the RB board in this case looks like it is incorrect.

 

[DougRim]

I agree that there is an error in the VASL LOS engine when checking LOS from AA22 to FF24.

But before we get there.

Simon, you are drawing your los incorrectly in both of the images that you submitted. As you will note, in both EE24 and FF24 the target hex is shown as "Virtual Location Level -1". This means that you have gone down one level from the actual level of a unit IN EE24 or FF24 which is Level 0 because, as apbills notes, the pink terrain on the RB Map is Level 1. "Virtual Locations" are something that I created a version or two ago in VASL. They allow you to go up to Level 10 and down to Level -3 (I think). These are locations that don't actually exist on the map but might be created by SSR (in the case of OffBoard Observers in particular or Level 3 buildings). Unfortunately, they can be confusing in instances such as this one.

Here is an image that shows LOS drawn to the Level 0 gully in EE24.

And, correctly I believe, it is shown as blocked (on my device a red line is clear and blue is blocked).

LOS to FF24 should also be blocked but is not. This is an error and I will investigate why.

 

[apbills]

This means that you have gone down one level from the actual level of a unit IN EE24 or FF24 which is Level 0 because, as apbills notes, the pink terrain on the RB Map is Level 1.

View attachment 21692

Just to be clear - I never called the level 1 terrain "pink", it is either "tan" or "light brown".
And I really like the virtual location capability!

 

[von Marwitz]

Just to be clear - I never called the level 1 terrain "pink",

You didn't? I thought you were the guy calling the color of the Germans "lavender", too...

von Marwitz

 

[Simon62]

Hi DougRim,

Yes apologies for my mistake on the LOS bead using the virtual levels, I had checked it without using virtual levels and then thought that the virtual levels may change the result but they didn't and I sent in the wrong screen shots - apologies.

The virtual levels are great, I did help you test them on one occasion, and are very useful for off board observers, height of OBA blast and aerial LOS but I agree I used them in error in this case.

Anyway, at least another small LOS glitch has been identified so can be looked at, as always thanks for all the work you undertake in the background to let us use this excellent system and as mentioned before please contact me if you need any help in testing things out I am always happy to help

Regards

Simon

 

[apbills]

You didn't? I thought you were the guy calling the color of the Germans "lavender", too...

von Marwitz

Somewhere in my kit I have some of those.