Possible zoom undocumented feature aka bug

When zooming out it appears the units move slightly lower most likely due to the text line that I have above the units.

The 101st HQ sitting on the road is the best measure of the event, as I zoom out it slowly drifts south.

Also this only shows itself with larger multiple maps like a Panzerblitz or Squad Leader. In this case it is an update to Panzer 44 trying to create Market Garden using Panzerleader/blitz/AIW maps.

The map is 32 maps tall and about 9 wide. On a 1x1 the effect does not appear to happen. I will see if I can determine where the trigger point is.

Using an older version of vassal, 3.5.8 and VSQL it appears to be happening there also


Does this happen with current Vassal (3.6.17) and current VSQL (4.3.4)?

Yes but pattern is different, at 44% it is off, 67,100 are fine, 150% it moves slightly south.

How far back can you replicate the problem? Does it happen with Vassal 3.2.17?

3.2.17 using Squad Leader it is slightly off at 39% zoom


100% it is on target


Can you replicate the problem in 3.6.19 with a minimal test module?

It still does it in .19 32 maps tall near the bottom it looks like this:

It is definitely tied to the multimap function, and if I put a unit at the top map it does not slide towards the bottom during different zoom levels, here is 25% zoom on top map no drift at all!


May not be worth the trouble trying to solve as it only happens with multiple maps on a very large build. But I thought I should report it. I have tested on monster game maps and they are not replicated and are fine, so it is only with multiple maps and larger numbers of them that the bug is displayed. Most likely this has been there since the multimap feature was put in the system, it’s just that it took a massive map build to show it.

If you want me to look into it, create a minimal module that demonstrates the problem. It sounds like you could do this with one repeated board and one piece, so I expect it won’t be that difficult.

I’ll build out something, the maps I use are 3300 pixels wide and about 1100 deep.

What version do you want me to build it with, I have 3.2.17, 3.5.8 and the .19 latest?

Please use 3.6.19. This bug seems to have existed for a very long time, so we won’t be needing to open the test module in anything older.

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I left out the hex zones as I think it may be partially masking the error. Here is the module, add 30ish boards and go to the bottom row and add the one unit and start zooming and watch it drift at different levels

I can reproduce the problem with your test module. Thanks.

Here’s the problem: Board tiles have integer heights, at every scale. Boards may not have integer heights at some scales. (E.g., a board which has an odd height will not have an integer height at any scale which is one over a power of two.) A small amount of error can accumulate with each row of boards you add due to this mismatch. With small numbers of rows, it’s not noticeable. If you have 30, though, it can become enough to significantly offset pieces (which are in the correct locations) from the board tiles which are drawn.

I’m not sure there’s anything we can do about this in V3.