Forums Technical Discussion Help, @orient "360 degree" problem

Help, @orient "360 degree" problem

   1853   6   0
User Avatar
hign
Member
27 posts
Joined: 2月 2022
Offline
 
for some reason, I need to use @orient to “rotate” copy-to-points’ orient

at most of time, the vex script works
but if the sphere’s segment is 6,12,24…, when they hit 360 degree(or 0? I’m not sure)
the problem rise (like the pig-heads in picture, they have “opposite” direction)





why this problem happens?
And how to fix it?

Thank you for you help

Attachments:
2023-03-03_10-05-27.jpg (303.8 KB)
2023-03-03_10-13-13.jpg (90.5 KB)

 Report
User Avatar
tamte
Member
9053 posts
Joined: 7月 2007
Offline
 
that code looks like you were trying to throw someone off of your scent
I genuinely got lost

try this
vector up = {0,1,0};
@orient = quaternion(  maketransform( normalize(v@N), normalize(up) ) );
Tomas Slancik
FX Supervisor
Method Studios, NY
 Report
User Avatar
hign
Member
27 posts
Joined: 2月 2022
Offline
 
tamte
that code looks like you were trying to throw someone off of your scent
I genuinely got lost

try this
vector up = {0,1,0};
@orient = quaternion(  maketransform( normalize(v@N), normalize(up) ) );


I’m a beginning leaner of vex(), the reply really helps me!!
Thanks a loooooooooot !!

As a beginner, still have some doubts in my mind, like

The first one
Still want to know,

Because I’m studying the function like quaternion（），cross(), qmultiply()…..
I really want to know
Why I rotate one axis, then the other, it works, except the 360 degree points
And ,how can I fix it(of course maketransform been learned)(for other scenario or example )
I think if I do not understand the reason, the same problem will happen again and again


Second，
The maketransform don’t work very well with the top and bottom points, witch the N and up axis is the same

If I need, how can I fix this in a good way ?


Thanks again!!!!
Edited by hign - 2023年3月3日 22:42:20

Attachments:
2023-03-04_11-34-31.jpg (323.4 KB)
2023-03-04_11-35-13.jpg (302.1 KB)

 Report
User Avatar
willh
Member
134 posts
Joined: 12月 2006
Offline
 
Hey, I have done something similar, but instead of just using the normals I do a cross between normals and a up vector{0,1,0}.
matrix3 matrix_ = maketransform(v@N,cross(@N,{0,1,0}));
@orient = quaternion(matrix_);
Im not getting any weird flipping on the poles

Attachments:
orient.jpg (357.6 KB)

 Report
User Avatar
Digipiction
Member
166 posts
Joined: 3月 2014
Offline
 
The poles will typically give you problems because the cross product between identical vectors is 0, i.e. not a valid axis. You can check the dot product between the vectors, and if it's 1, then you'll want to choose a different second vector. So something like:
vector up = set(0, 1, 0);
if (dot(v@N, up) == 1)
  up = set(1, 0, 0);
vector side = cross(v@N, up);
 Report
User Avatar
derrick
スタッフ
334 posts
Joined: 7月 2005
Offline
 
hign
I really want to know
Why I rotate one axis, then the other, it works, except the 360 degree points
And ,how can I fix it(of course maketransform been learned)(for other scenario or example )
I think if I do not understand the reason, the same problem will happen again and again

The problem with your original code is how to handle situations when @newz and @mytan point in opposite directions. In these situations, dihedral() will return an arbitrary rotation that will map @newz onto @mytan but you want to further constrain it to a rotation that will keep the @N direction unchanged.
Edited by derrick - 2023年3月20日 10:13:31
 Report
User Avatar
hign
Member
27 posts
Joined: 2月 2022
Offline
 
thanks for everyone. still studying it, above notes help a lot!
 Report
  • Quick Links