Rotation Check

remus

An interesting feature of a transformation matrix is that its determinant will always be 1 if it is a rotation or combination of rotations so i wrote this little snippet to test whether a given transformation matrix consists solely of a combination of rotations.

Probably not much practical use but someone might find use for it somewhere.

A little word of warning, it'll also return true if you just input the identity matrix (which i suppose is technically a rotation of 0 degrees.)

def rotation_check(trans)

arr = trans.to_a
a1 = arr[0]
a2 = arr[1]
a3 = arr[2]
a4 = arr[4]
a5 = arr[5]
a6 = arr[6]
a7 = arr[8]
a8 = arr[9]
a9 = arr[10]

det_arr = a1*(a5*a9-a6*a8)-a2*(a4*a9-a7*a6)+a3*(a4*a8-a7*a5)

if det_arr == 1 and arr[14] ==0 and arr[13] == 0 and arr[12] == 0
  true
else
  false
end#if

end#def

Chris Fullmer

if the transformation is moved off 0,0,0, it will not return 1 yeah? And if the comp has been scaled or skewed it does not return 1, right? Those are the things it checks for more or less, right?

Chris

remus

No, it will not return true in any of those cases. Having said that, if i was less lazy it would be fairly trivial to get it to check for translations and 'skews, scales and rotations' (although not each separately.)