I want to draw a cylinder which has a different and irregular cross section along the cylinder length, with precise measurements

enter image description here?

At each angle the cylinder has a specific radius, therefore the cross-section shape is nor regular. (like the figure)

  • $\begingroup$ Hi and welcome to Blender Stackexchange. Blender's primary focus is on modeling and rendering, it is not a CAD software. If you expect precise measurements you need to use a CAD software. $\endgroup$ – metaphor_set Mar 22 at 17:24
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    $\begingroup$ Do you want to derive this from a data file? If so, what format would you use? $\endgroup$ – Robin Betts Mar 22 at 17:29
  • $\begingroup$ @metaphor_set, Blender can be used for some CAD purposes with absolutely no problems(or some insignificant problems). There is no need to send people away to other software straight away. It's just important to keep in mind that Blender holds its numerical values in 32 bit float format as opposed to 64 bit floats used in most CAD software so it is possible to run into precision issues. You do not necessarily run into problems in every single case - 32 bit floats can still hold quite a lot of precision. $\endgroup$ – Martin Z Mar 22 at 19:24

If you need to work in micrometers, it is better to select None as the Length unit and just keep in mind that the scene unit is micrometer, because Blender starts malfunctioning if you try to scale units to that size even if you do that with unit scale value:

Unit settings

It is easier to create the cylinder then it may seem. We could use vertex slide functionality(shift+v) to quickly and easily specify the lengths of the radii. Vertex slide works proportionally to the edge it slides on and we want to enter units instead of proportions during the slide operation, so let's adjust the proportion to match the units by making a circle that would have a radius of 1 unit. Once you have the circle, enter edit mode (tab) select the edge loop and extrude it(e), scale it in a bit (s), extrude again and merge the loop to center with alt+m. Now you can take the vertices one by one. Slide every vertex (shiftvv) to the center, slide it again, hit c to clamp it to the path so it can go further than the edge loop marking 1 unit, and enter the units before confirming the operation with a mouse click. Repeat this for all vertices around, once you are done, you can delete the 1 unit mark edge loop, select everything and extrude:


  • $\begingroup$ Thanks a lot, one more thing, Is it possible to change the cross section of the cylinder along its length (its cross section is varying along its length, its thickness is varying) $\endgroup$ – Muhamed Sewidan Mar 23 at 9:02
  • $\begingroup$ You could extrude the first time up until where it changes, then scale(s) the top that is soon to be a cross section to whatever thickness you need and extrude again. Please be more specific if that's not what you are after. The word 'change' can mean thousands of different things. $\endgroup$ – Martin Z Mar 23 at 14:17

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