Visualize all calculated trajectories in RViz

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I have a Nearness Diagram node, which is gap/valley based so as with your description it calculates several possible 'paths' before selecting the best one to attempt to follow. I use RViz to visualize these by creating line strip markers, there are several different types of markers that you can use, though you may need to perform a few extra calculations in order to get the values you want for displaying in RViz. By doing this I can see all of the possible 'valleys' found at any given time. With even more work you could even go as far as to generate a nav_msgs/path which RViz will display but if you're just trying to do simple testing/debugging I wouldn't recommend this as it will be a lot of extra effort. A simple line strip marker works great for me, and if I don't want to see excessive markers while testing I simply uncheck the display in RViz.