Selecting only some of the outside faces

I have an object that I scanned in. Before I print it, I want to smooth one side of it. Before I get to the smoothing, I need to select the wavy part you see outlined in purple in the image below.

I had to manually tediously select the edges for the loop, via Shift+RMB, resulting in the following. Is there a better way to do the selection of this loop?

After using the Select Loop Inner-Region tool, Blender choose the “inner part” the wrong way as shown below. o.o

I want the inverse of what Blender selected. Is there some way to make Blender choose the vertices the other way around?


STR+ I, or Select Menu Inverse…

Maybe this: face select mode, select one face on each flat side, ctrl+alt+shift+F to select linked flat faces, operator panel to adjust the angle limit. Then invert selection with ctrl+i. If you need just the purple edges, could do select menu -> select boundary loop.

The reason it doesn’t allow selecting those as edge loops is because there aren’t any, it’s a triangulated mesh. Could try turning some of them to quads but I think the most useful thing is not having to select edges like that again: select shortest path by selecting a mesh element then ctrl+select another one much further away and it selects the shortest path between them. If you need to select two paths that aren’t connected, could shift select another point and continue with shortest path selection.

Yea it doesn’t always know the right direction. Could invert the selection or toggle “bigger” option from the operator panel that is visible on the screenshot. (Bottom of the tool shelf, or F6, available after using some function/operator).

I tried this, but it also included some the main edges of the whole shape. I thought that the shape had some really small faces or something that I ended up not seeing, but I could not find anything like that.

I always thought meshes were made of triangles and that was that. Rectangles are possible too? Well, I tried converting to quads but it still left many triangles. Also selecting an edge loop did not really do what I wanted. However, your suggestion to select the shortest path helped cut down the time a lot. Thanks.

These tips worked well. Thanks.