"Francesco" <nas### [at] gmailcom> wrote:

> Calculating area triangle per triangle I can always suppose z=0 (translating and
> rotating axis) as triangles are 2D. So I think the formula posted by Penelope20k
> is good.
>
>
> Francesco

YES ! it is not only good but great. it is the shortest route from points to
area I have seen.

just I am not able to mentally make the leap to 3D without a lengthy conversion
to 3 side lengths. If I could, it might be the shortest route in 3D.


also note that 666... is common to all tetra and pyramid volumes?!?

  ; //e $tetrahedron_volume(383 156 0, 645 254 0, 465 289 0,400 200 200) =
893666.666667
  ; //e $pyramid_volume(276 308 0, 383 123 0, 666 324 0, 276 308 0, 400 300 200)
= 2462066.666667


I have finished the volume macros

#macro tetrahedron_volume(A,B,C,D)
  #local result = abs(vdot(D-A,vcross(D-B,D-C))) / 6
  result
#end
#macro pyramid_volume(A,B,C,D,E)
  // perimeter order for 1st 4 points
  #local result =
     tetrahedron_volume(A,B,C,E) + tetrahedron_volume(A,C,D,E);
  result
#end

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