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I have two skulls like so: enter image description here

Using the 3D print addon toolbox, I know the volumes of each:

  • 747735056401 for the larger one
  • 569718590290 For the smaller one

I'd like to scale the smaller one to be the same volume as the larger one. Not being a math wiz, I simply did: 747735056401/569718590290= 1.312464, so I hit S and typed in 1.312464.

But, I didn't even realize that would just scale the x,y,z dimensions and all of a sudden my new volume had gone way up to 12880819961337. Way larger than intended.

Does anyone either know (through a Blender command, or through better math understanding) how I could scale the volume of one to be the same as the other?

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The volume is proportional to the cube of the scale. For example, doubling all of the dimensions would result in a volume that is 2x2x2 = 8 times the volume.

Therefore, in order to scale the volume by 1.312464 you have to scale each dimension by the cube root of 1.312464. ie, approximately 1.0948678.

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  • $\begingroup$ This probably falls into "I should have googled this" but thank you! $\endgroup$ – Joe Crozier Jan 29 at 20:00
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    $\begingroup$ No worries. Actually, you can get Blender to do the maths for you also - since you can type equations into fields and operators. Simply select the object and type s1.312464***0.333333<Enter> and Blender should scale it for you. Here the S is for Scale, the numbers enter the scale, the first * seems to be necessary to end the number (don’t know why) then ** is the power operation and 0.333333 is 1/3 (or near enough) for cube root. $\endgroup$ – Rich Sedman Jan 29 at 20:35
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    $\begingroup$ That's odd.. I have no problem with 2**.333 , 2**0.333, 2**(1/3) ... Linux 291 $\endgroup$ – Robin Betts Jan 30 at 4:55
  • $\begingroup$ Thanks for the feedback @RobinBetts. I’ve tried this on two Windows 10 systems (one with Blender 2.91 and the other 2.83.6) and both are needing three *s for this to work. Very strange indeed. $\endgroup$ – Rich Sedman Jan 30 at 7:48

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