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Getting good edge flow – extruding from the side of a truncated cone

Go to solution Solved by Cerbera,

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Hopefully someone out there can help me with getting good edge flow on my model.

In the images attached you can see I am trying to extrude two tapered cube shapes from the side of a truncated cone. I am trying to model a pair of headphones for practice and this piece is where the headband and the earcups are joined.

I am having an issue with not having enough geometry to attach my control edges on to so that I can tighten all the edges of the headband slots (the slots are meant to be square not a rounded shape). 


I have been trying to keep the poly count down but could the issue be that I do not have enough rotation segments?


Another issue is there is pinching around the corners when viewed at certain angles which I hope will be resolved by better edge flow.


Any feedback as always will be much appreciated 😅

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Ah yes, it's the old 'not enough radial segments' issue again... and there's no need for horrible triangles anywhere here...

You need around 96 - 128 segments for that part, so you can pull those tabs out of there with no disturbance to SDS surface curvature... like so...






Because it is a radial form there is no real disadvantage to working with this many polys - it's more or less the same amount of work as working with much less because most subsequent modelling operations on this part will involve double clicking entire edge loops, and scaling or extruding them. The example below shows how we could carry on expanding that if we needed to...




Now you can do it in less polys than that, but there is usually no reason to, when this gets a totally flawless rendered result, and remains 100% quads.

You should be building this model in the same separate parts as how it is in the real world, which means only this metal part has to be so poly-dense. the rest of the speaker could remain much lower poly, more in the order of 16 radial segs...





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Thanks for your detailed feedback. Would you mind showing me the base mesh as well? Ideally it would be good to see the working file so I can inspect how you have done your control edges to get a tight shape on the tabs. I have tried 128 rotation segments which is a lot easier to work with so I’m definitely getting there.


One thing I forgot to mention is when looking at the top of the model the two tabs are meant to be rectangular. Just extruding the polygons on the angled surface, when viewed from above, actually gives a parallelogram shape which is not 100% what I am after. But obviously if this is too problematic I will compromise for the sake of good geometry 🙃

Screen Shot 2020-10-21 at 09.12.58.png

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I think Jay simply select polygons, extrude up/(Ctrl_Clone), scale to 0 at the top, add support edge loops at the top and bottom of extrusion...


base polymesh should look like this


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2 hours ago, LeChuck said:

Would you mind showing me the base mesh as well?


That WAS the base mesh, or rather the base mesh looks almost identical to the SDS result !! And Lubo is correct as to how I did the tabs. The base poly level is dense enough that you don't actually require control loops there, except as shown above on the extruded tab sections.


Here's the file if you'd like a look round that...


SD cylinder details.c4d


If the tabs are truly rectangular at the base but emerge from a tapered part then there is an additional stage you need to do in between selecting the polys and extruding them. You would do a small inner extrude giving you an extra row of points you can slide tool into a perfect rectangle by lining it up against a guide shape in an orthographic view. This will be fine as long as long as you don't need to move the polys (externally) surrounding that new loop. If that is the case you can step down resolution to as low as 64 radial segs whilst still using this technique. Any further and you will require additional controls, for which there are other, more suitable techniques...



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Here's that technique I mentioned above in action, although here I felt it was enough to use a perspective view to get 'head-on' to the section in question, and I used the knife tool (line cut) directly to cut a perfect rectangle into the tapered form, then connected to the corners of the next poly loop out to retain 100% quads.




At this point you could now use the Slide Tool,  in Points Mode, to move the inner points about to give you even controls without leaving the tapered surface.

We should also note how helpful Symmetry would be at this point, so you only had to do this once, on one tab, and it would get mirrored to the other side.


If you've done this right you will still get lovely transitions and no distortion...




If we look at the topo for that now you will see that once I had got my rectangle I then did a tiny inner extrude of those polys before pulling them out, to more fully redirect the edge flow around that shape rather than across it... now - on a lower res mesh that would cause lumps and bumps when under SDS, but doesn't here because the difference between control polys and regular ones remains minute - all because we have enough segments in our base mesh to nail down / describe the curvature there...




Lastly, you may be wondering why I have allowed such relatively big long polys on the extruded tab bit. We could just as easily add a few more loops into that section, and that would indeed be a wise thing to do if we were UV mapping this object for example - where regular poly density all over the mesh would lead to least texture distortion. But if no UV's are needed then the additional loops remain optional here, for polygon efficiency reasons; we only need the 2 control loops because that surface is largely planar. However, were this for a client, who did not have poly efficiency concerns, then I would invariably add them anyway for the sake of consistency and completeness (and to a much lesser degree) for maximum wireframe visual attractiveness, which the client won't give 2 sh*ts about, but will look great in my showreel gallery !! Make sense ?



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Thanks Cerbera your technique has worked! Genius, thank you for your help. 


I used your technique of drawing the square in the orthographic top view and then joined them to the outer polygons. Then I did the smaller inner extrude. Then I extruded the square shape up and flattened out the top. This top shape was made slightly thinner on the x axis to taper the shape (this caused the sides of the tabs to become non-planer but it is under 2º so I set my Planarity Threshold to 5º). 


I also rearranged the points on the top of the tabs to match the desired slot shape and also evenly distributed the edges. Then I played around with the control edge loops to get everything looking tight. 

All in all, very happy with the way it has come out. I have also attached a picture of this piece with the other parts of the headphones, which you can see have a lot lower polygon density as they are very simple shapes in comparison.


Thanks again


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