Round walls are not really round (anyway roundness doesn't exist in Java3D and OpenGL which handle only triangles) and you can see how many points are used to approximate a round wall when you double-click to create a room surrounded by round walls.
If you look closer to the points of the room created that way, you'll guess that the wall aren't generally symmetric and that's why you get the problem you reported. So, either you try to change wall length and/or thickness step by step until it's symmetric, or with the (quite complicate) following formula used to compute the step between two points of a round wall, try to find which thickness, arc extent, and/or radius will give you an integer (with no decimals):
step = squareRoot( (thickness/2 + radius) x arcExtent x π / 180)Suddenly, I feel you hate me!
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Emmanuel Puybaret, Sweet Home 3D creator
