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I want to create a model of the street lamp post. The bottom 1 meter in length is ROUND and then there is a 0.45 meter ROUND tapered part. Then there is the top of the post which is OCTAGONAL. I have created the bottom 2 sections but not sure how to extend the post from round to octagonal within adding a new mesh object. Is there a method to extend my post without adding another mesh? Here is what I have done so far. I have added an image of the actual light post showing that the base is round in shape and then the post is octagonal with NO transition between the two just metal welding. Not similar to the 'pencil' method. enter image description here

enter image description here

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There is an important distinction that needs to be made. In Blender, an "object" can consist of multiple distinct meshes - meaning that a single "object" can have several parts that are not joined together.

From what I know, this is the easiest way to achieve what you're looking for:

  1. Enter "Edit" mode with your lamp object selected.

  2. Use Shift + A > Circle to add a circle mesh. Since we are in the "Edit" mode for the lamp object, the circle mesh is added as part of the lamp.

  3. Change the circle to have 8 vertices.

Add Circle Box

  1. Rescale and position your octagon where you want it to join to the lamp post.

  2. Select the octagon and the upper edges of your lamp post.

  3. Press Ctrl+E to bring up the "Edge" menu and select "Bridge Edge Loops." Note that the "Edge" menu can be accessed at the tabs near the top of the window. You can also use the F3 search menu to find the "Bridge Edge Loops" function.

enter image description here

enter image description here

Edit: From the reference photo, it seems that the transition between circular and octagonal that you're trying to replicate is a weld.

For something like that, I would use sculpting. The general idea is to use "dynotopo." Dynotopo adds additional vertices as you sculpt, which can make the topology really messy. However, if you isolate the messy geometry, you can get the smooth lamp pole and the clumpy weld transition zone.

Set the model that was created using the steps above to use "Shading Flat" and then go to the "Sculpting" workplace.

Before sculpting, enable "Dynotopo" in the top right-hand corner. You can sculpt using a variety of tools, but I just used the default "Draw" tool.

Note that you may need to click the "-" button at the top of the screen to get the tools to build on top of the model, rather than cutting in.

While sculpting, make sure that you do not change the model geometry above/below the transition faces (marked with the blue lines).

enter image description here

After you're done sculpting, head back over to the "Layout" workspace. Enter Edit mode, press A to select all, then go to Mesh > Clean Up > Limited Dissolve.

enter image description here

If you were careful not to edit any of the geometry outside the transition area, you'll get clean geometry above/below the weld area, and the messy welds in the center.

enter image description here

In the case that the "Limited Dissolve" command also deleted a vertex or two off of your circular/octagonal edge loops (as it did for me), enter edit mode with Tab and press Num1 or Num3 to go to the front/right orthographic view (use CtrL + those keys to go to rear/left orthographic).

Then, press K to use the knife tool. Click on the two surrounding vertices to add the edge. Press Enter to confirm the extra edge.

enter image description here

Now, this step is not necessary, but you may find that it helps improve the final result. Press K to use the knife tool again, press A to snap angles, then press C to cut through the entire mesh, then add an additional loop cut across the top/bottom of the transition area.

enter image description here

Now, Ctrl+click on the vertical edges on the octagon to select all the vertical edges. Then press Ctrl+B to bevel the edges. enter image description here

Finally, go back to object mode and set the shading to "Smooth Shading." You should have something that looks fairly close to the reference image.

enter image description here

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  • $\begingroup$ Thanks and very interesting and and something new (bridge loops) for me to learn. However this will not replicate the real post which is round in shape all the way and then changes to hexagon, not a 'transition from round to hexagonal. Maybe the only method is to create another mesh to create the top hexagonal section and join them. Maybe I am 'nit picking' too much and no one would ever notice the difference. Thanks again. $\endgroup$ Jun 15, 2022 at 4:14
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    $\begingroup$ @JohnArnold Edited the answer. Its quite a bit longer now to accommodate adding the welds to the middle :) $\endgroup$
    – stphnl329
    Jun 18, 2022 at 4:26
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    $\begingroup$ The number of vertices the sculpting process would add varies based on how much bumpiness you add while sculpting. You can also increase the angle when using "Limited Dissolve", but this is limited to the point that you start deleting too much geometry. $\endgroup$
    – stphnl329
    Jun 19, 2022 at 9:33
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    $\begingroup$ @JohnArnold What I mean is this, if you don't like the transition between round and octagonal and don't want no weld either, just do this: simple change - this could also be used similar for moonboots solution: second version $\endgroup$ Jul 7, 2022 at 13:45
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    $\begingroup$ @JohnArnold Yes, I've understood it's not that you don't like the weld, it's because of the polycount. That's why I said you don't "want" it ;) But you don't like the transition it seems. But isn't my suggestion then okay? Not so many polygons as a weld and not such a long transition. $\endgroup$ Jul 8, 2022 at 10:06
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You can:

  • Create a 8 vertex circle, select all in Edit mode and CtrlB then V to bevel the vertices (to increase the number of segments, use the mouse wheel, or the "+" of the numpad, or type it in the Operator box which is at the bottom left of your 3D view):

enter image description here

  • Keep the octagon selected, Shift select the top of the cylinder, right click > LoopTools > Bridge (LooptTools is an addon that you need to enable):

enter image description here

Or:

  • Create a 8 vertex circle, select all in Edit mode and CtrlB then V to bevel the vertices:

enter image description here

  • Extrude down, keep the bottom edge loop selected and right clic > LoopTools > Circle:

enter image description here

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    $\begingroup$ +1 The second solution is what I would've suggested. For the first solution it might be helpful for beginners to mention how to adjust the number of bevel segments, so that the Bridge tool works as expected. $\endgroup$ Jun 14, 2022 at 9:20
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    $\begingroup$ ok, done, I've edited ;) $\endgroup$
    – moonboots
    Jun 14, 2022 at 9:23
  • $\begingroup$ Thanks. I am a beginner and as such will favor the first method. Thanks to you both. I am now thinking that to make the model the same as the real one I want to retain the circular shaped tapered part and solution 1 appears to modify the shape of that tapered section so that it is round at the bottom and almost octagonal at the top. Maybe I need to create an octagonal cylinder via mesh circle with 8 vertices and join it to the base but maybe it might not look good however the real post is that way and the octagonal part is welded to the round base. $\endgroup$ Jun 15, 2022 at 3:38
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I just started so there may be better ways to do that, but my first thought is to start with a 64 vertices cylinder, then when you have your extruded and tapered part, you go in edit mode and edge selection, and you select your edges two by two, hitting x and "collapse edges and faces" each time, so you divide the number of edges with each iteration. Here is my result Octogonal top part

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  • $\begingroup$ By the way 64 could be 32, 16, 128, just 2^n*8 vertices $\endgroup$
    – Hugo Hans
    Jun 14, 2022 at 8:04
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    $\begingroup$ The mesh, however, is uneven in the collapse. Nice attempt, anyways :) $\endgroup$ Jun 14, 2022 at 8:30
  • $\begingroup$ Yeah... But now I know how to do it too ! $\endgroup$
    – Hugo Hans
    Jun 14, 2022 at 8:45
  • $\begingroup$ Thanks but once again (as mentioned in my replies above) I want to try and replicate the real post which has an octagonal post welded to the round base - the round base (taped top part) is completely round shaped and then 'changes' to an octagonal (top) part - see image of the real post added to original question. $\endgroup$ Jun 17, 2022 at 7:38

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