Trying to extend an edge along a curve

Question

First, I cannot draw a straight line with a ruler. I have NEVER been artistically inclined, however, blender seems to help me overcome SOME of my issues. I can edit basic models and get close to what I really want. lol

With that being said, I have a model (I am not the author of the model), that i need to extend the edges pointed at by the arrows. That "bump" need to be smoothed out. I want to extend it so that the "bump" is now a smooth transition from the ground plane.

My issue is that I can extend the edges, but it does NOT maintain the dimensions I need.

If I made the model, I would have created an outer and inner circle to attach those "bumps" to. With that being said, I do NOT know how to make an inner and outer circle to attach the edges to so that the edge of the model continues to follow the dimensions of the circle.

If I select the edges and grab them, I would want the individual rectangles to shrink as they get closer to the center and expand when it gets further from the edge.

I hope my explanation and pictures are clear enough.

Once I figure that out, I SHOULD be able to cut this into 45/30/10 degree curves!

If there is a youtube video, that shows what I want, please send me the link.

Otherwise, I would need fairly complete instructions.

If I need to make a circle, I can do that, however, I have NO clue how to center it on my existing model, or make my model center on the circle. OR even size the circle so that it matches the radius on the inner and out edge of the model.

I know how to alt-click to grab edges/faces/vertices, S + axis scales, etc... but some of the more in depth stuff, I have yet to learn.

I appreciate any help on this!

Answer 1

Overview:

The thing you are struggling here is a Pivot center for rotating/scaling.

In your situation as you stated that model isn't yours we will need to manually place 3D Cursor at the desired spot and then switch to Pivot center: 3D Cursor and we are good to go. Normally when you are creating such shape it is (mostly) in the center of the scene so the first steps wouldn't be necessary.

Steps:

1. Grab two vertices on the inside of the mesh like in the gif.
2. Press F to make an edge and connect them.
3. Press W > Subdivide to create vertex in the middle of created edge.
4. Turn on Vertex Snapping.
5. Press G > Y and hover mouse over the bottom most Vertex. Repeat with X Axis.
6. Shift+S > Cursor to Selected to place 3D Cursor where we've moved our vertex.
7. Delete this vertex, it's no use now.
8. Select Pivot center to 3D cursor.
9. Select inner/outer edge loop and Extrude/Scale or both.
10. Optionally go to Object Mode and set Origin Point to the 3D Cursor, it should help later on. Do this by pressing Ctrl+Alt+Shift+C.