Finding a right angle to a normal

[LaidlawFX]

Hello,

I am trying to get a 90 degree angle to a normal to re-orient my normal so I can use a peak sop tangential to a curve. If needed I can provide the upvector, which by default is in the positive Y direction.

My test case is that I have a circle(curve) with each point normal looking at the next point in the circle(curve), via point sop with a sort or vop sop. My circle(curve) is on the XZ plane, and my upVector is pointing up in the positive Y by default. So I should be able to find a 90degree angle to my normal that I can peak something along, call it finding a Z-axis for each points co-ordinate system. I believe this is a simple vector match problem for vop sops, but I'm stumped at the moment, how to get this Z-axis as a second vector.

As for cheats I do not want to use another curve scaled in to orient with because with complex shapes you can not get an even angle set on the normal's.

Thanks

-Ben

[hopbin9]

I am trying to get a 90 degree angle to a normal to re-orient my normal so I can use a peak sop tangential to a curve. If needed I can provide the upvector, which by default is in the positive Y direction.

If Y is always up, then a simple VEX SOP can transform the normal by 90' on the Y axis. Just take the P normal from the global input, and then use a VEX transform. Optionally write out the new value to an attribute instead of replacing the input normal.

[LaidlawFX]

If Y is always up, then a simple VEX SOP can transform the normal by 90' on the Y axis. Just take the P normal from the global input, and then use a VEX transform. Optionally write out the new value to an attribute instead of replacing the input normal.

Thanks... lol, one node, how sad...

[hopbin9]

Thanks... lol, one node, how sad...

Actually, i was wrong. There is a Rotate node. See the attached example. Attribute "R" is rotated by a parameter, based upon the UP and Normal vectors.

vector-angle.hip

[LaidlawFX]

That's def a more tool worthy solution. I think this was something more of what I was originally looking for, for versatility, since it is capable of calculating the inbetweens.

Thanks again.

[sam.h]

A cross product gives you a vector perpendicular to both input vectors.

I think of it as the the two input vectors defining a plane, then the result of a cross product is the normal of the plane.

Also, if all you want is a tangent, use the polyFrame SOP to give you tangentu and/or tnagentv.

[gaurav]

Just to add few things.

1. Order matters in cross product. Up X N or N x Up will determine the direction of resulting orthogonal vector.

2. Polyframe is handy yet mysterious

Cheers!!