complete n00b - constructing a tetrahedron

Technical Support Modeling
1

as the title says, complete n00b, here. been playing with blender and finding
the current version much easier to work with than when i’ve looked at it in the
past.

i’m anything but a math guy, so i couls use some very direct help. the task i
have is to construct four identical tetrahedra that i can fold together to make
a single, equilateral one. i’ve actually gotten something like this to work in
my testing but it’s not right proportionally and needs refining.

the way i made the first tetrahedron was to make a cone, give it 3 faces and
then copy it three times. this all worked fine except that i might not have
made it to the right size when i started. the way i did it was to use the ‘scale’
property with values of 2.0, 2.0, and .3. that gave me a tetrahedron that,
when multiplied and folded folded up, fit together fairly well.

my question: what are the actual numbers i should use for the height if the
other two values are 2.0?

thanks,
BabaG

2

http://en.wikipedia.org/wiki/Tetrahedron
To make a tetradedron in blender you can enable the 'Regular Solids’ addon to enable you to add a range of solid objects

3

thanks for the tip about the addons. i’ll look at that when i get back to blender.
as for the wikipedia link, i’ve looked at it and it’s completely martian to me. i
get the basics but the terminology and formulas are just martian. that’s why i
included the dimensions i was using in my post. hoping someone who does
understand this stuff can just give me a number i can plug in.

thanks again,
BabaG

4

Why not just add 4 tetrahedrons with the Regular Solids addon as Richard suggested? You are going to get the same result but without having to figure this out yourself.

If you really want to do it yourself, the height of the tetrahedron is ((6^.5)/3)*length of a side.

You can force the “cone” to be a tetrahedron by adding a cone with 3 sides, radius 1, and height of 1.4125390850049660366271004830804 (recommend a copy-paste on that last one.)

Once it is added you have to always scale the object on x, y, and z to keep it a tetrahedron.

5

You can also turn the default cube into a tetrahedron if you join faces like this:
http://i49.tinypic.com/2h2edg0.jpg

You can then scale the cube to get a non-regular tetrahedron.

6

thanks for all the replies, especially the numbers.

looked at the ‘regular solids’ thing and would like to try
it but was confused. for one, it said it was for blender 2.5.
also, it said it was in an ‘addons’ menu that i didn’t see.
complete n00b, as i said. will continue looking into this.

thanks again,
BabaG