Rotate cameras from vector list to degrees

[konstantin magnus]

I have read lots of camera angles from a text file, and try to convert them from vectors to degrees:

rot_list = rots.split()
# ['0.768704', '-0.628123', '-0.120648']
rot_deg = hou.Vector3.angleTo(rot_list)
node_camera.parmTuple('r').set(rot_deg)

It throws an error: unbound method angleTo() must be called with Vector3 instance as first argument (got str instance instead)

Edited May 16, 2018 by konstantin magnus

[3dome]

it's not really clear what [ '0.768704',  '-0.628123', '-0.120648' ] is. Is it the xyz values of the camera's rotation or is it the vector the camera points to? (like houdini cam points to (0, 0, -1) by default)

I'm asking because angleTo() returns the degrees between 2 vectors as a float value.
So your code would fail because you dont specify the first of those 2 vectors. the line should be something like rot_deg = hou.Vector3(0,0,0).angleTo(rot_list)

next issue - your error message: the list returns the values as strings (notice the ' ' ). so you might add a step and fix that like so: myVec = hou.Vector3(float(rot_list[0]), float(rot_list[1]), float(rot_list[2]))
and then use rot_deg = ... angleTo(myVec) with proper vector3 as argument

still, you then try to set a single float to the parmTuple('r') wich is not gonna work as it expects a sequence of values

 

In case of it being radians you could

import math
and with math.degrees(float(rot_list[0])) convert it to degrees
save that in a list and try feeding that into parmTuple.set()

Edited May 16, 2018 by 3dome

[konstantin magnus]

Hi Dominik, thanks for your help.

8 hours ago, 3dome said:

it's not really clear what [ '0.768704',  '-0.628123', '-0.120648' ] is.

Its a vector deviating from {0,0,-1}, exactly like the line SOP. So I am still looking for a method to convert this 3d vector to 3 degree values rx, ry, rz.

How is this usually done in Python?

[3dome]

i dont think python has built in methods for that but you can do it with some math:

https://stackoverflow.com/questions/15101103/euler-angles-between-two-3d-vectors
https://stackoverflow.com/questions/10706708/find-x-y-z-rotation-between-two-normal-vectors

[vicvvsh]

Hi Konstantin!

If i understood you right it must be working. 0,0,-1 is initial direction for a camera, rotDeg is vector with rotation in degrees.

def vtd(vector):
    vec = hou.Vector3(vector).normalized()
    m4 = hou.Vector3(0,0,-1).matrixToRotateTo(vec)
    m3 = m4.extractRotationMatrix3()
    rotDeg = m3.extractRotates()
    return rotDeg

 

[konstantin magnus]

Thanks to both of your help I was able to make it work:

Just one more question: How can I change the matrices so that the cameras are not rolled sideways?

[vicvvsh]

Try this:

def vtd(vector):
    vec = hou.Vector3(vector).normalized()
    initDir = hou.Vector3(0,0,-1)
    initUp = hou.Vector3(0,1,0)
    
    m4 = initDir.matrixToRotateTo(vec)
    dir = initDir * m4
    up = initUp * m4
    newUp = dir.cross(initUp.cross(dir))
    mrx = m4 * up.matrixToRotateTo(newUp)
    
    m3 = mrx.extractRotationMatrix3()
    rotDeg = m3.extractRotates()
    return rotDeg