How to Rotate a Non-Perpendicular Primitive to Align with the X-Axis?

[Tomoka]

Hi,

I’m currently working in Houdini and trying to rotate a non-perpendicular primitive to align it with the X-axis. In the second image, I used a Transform node and manually adjusted the rotation to achieve the alignment.

Is there a procedural or more accurate way to achieve this? Any tips, improvements, or alternative approaches would be greatly appreciated.

Thank you!

 

Edited November 28 by Tomoka

[toadstorm]

given two points on the long edge of the rectangle, let's say they're point 0 and 1:

 

vector p0 = point(0, "P", 0);

vector p1 = point(0, "P", 1);

vector n = normalize(p0 - p1);

// compute matrix that rotates the normalized edge onto +X

matrix3 d = dihedral(n, {1,0,0});

// transform points with this rotation

@P *= d;

[Tomoka]

It worked! 

Thank you so much!