destructive behaviour when lines overlap about vispy HOT 1 OPEN

I believe this is expected. You'd have to change the GL drawing state to something that works for your use case, but it may produce other artifacts. What you're describing is blending. You can see the LineVisual uses the "translucent" GL state preset here:

The properties used by this "preset" are defined here:

You can customize this I believe by doing my_visual.set_gl_state(preset="additive") or passing specific property values as keyword arguments to this method. That said, I would have thought translucent would have done what you wanted given the options shown but maybe I'm not thinking about this hard enough. It could also be GPU dependent given you're likely using the "gl" method of drawing the lines. You could try the "agg" drawing method provided by the LineVisual and see if that changes your results.

Let me know what you think and how these goes. Otherwise if @rougier knows this off the top of his head he could maybe answer more concretely.

from vispy.