Forums Houdini Indie and Apprentice find degrees between 2 vectors

find degrees between 2 vectors

   7660   4   0
User Avatar
olivierth
Member
1004 posts
Joined: April 2017
Offline
 
Hi!

I'm testing a detail wrangle that should find the angle in degrees between 2 vectors but the result is off. Where's my mistake?

vector v0 = normalize(set(-1,0,-1));
vector vref = set(0,0,-1);

float dot = dot(v0, vref);
float radians = fit(dot, 1, -1, 0, $PI);
float angle = degrees(radians);

f@rotation = angle;

-Olivier

Attachments:
find_degrees_angle_fail.JPG (51.7 KB)

 Report
User Avatar
BabaJ
Member
2036 posts
Joined: Sept. 2015
Offline
 
Dot product alone isn't enough.

In my sample file I've commented on the single line that does it.

The rest you set up differently to however it works for you.

Attachments:
Angle Between Two Vectors v1.hiplc (70.8 KB)

 Report
User Avatar
olivierth
Member
1004 posts
Joined: April 2017
Offline
 
Ah!

So I had to do this:

vector v0 = normalize(set(-1,0,-1));
vector vref = set(0,0,-1);

float radians = acos(dot(v0, vref));
float angle = degrees(radians);

Thanks!

-Olivier
 Report
User Avatar
wlvl
Member
23 posts
Joined: July 2015
Offline
 
In case is helpful..

If you want the rotation value in degrees for each axis component.

vector v0 = normalize(set(-1,0,-1));
vector vref = set(0,0,-1);

vector4 orient = dihedral(v0, vref);
vector angle = qconvert(orient);

angle = degrees(angle)*-1;
v@angle = angle;


You could reference the angle attribute in the rotation parameter of a transformSOP.

tag: rotation in degree for each axis component from direction vectors
 Report
User Avatar
tamte
Member
8525 posts
Joined: July 2007
Offline
 
wlvl
If you want the rotation value in degrees for each axis component.
...
vector angle = qconvert(orient);
angle = degrees(angle)*-1;
...

that doesn't sound correct
qconvert() will convert quaternion to angle/axis vector representation and that's different from per axis euler angles
to get actual euler angles you'll need to use quaterniontoeuler instead
...
vector angle = quaterniontoeuler(orient, 0);
angle = degrees(angle);
...
Edited by tamte - March 29, 2020 11:59:07
Tomas Slancik
FX Supervisor
Method Studios, NY
 Report
  • Quick Links