Houdini Script

$YMIN

on translate node Y translate field.

put the object on the 0 ground.

Houdini Attribute Wrangle 

Normal Vector Rotation

Rot value 3.14 is 360 degree of rotation as radian.

Houdini Normal, Left Right Veter creation vex

on attribute wrangle

vector up_vector = {0, 1, 0};

@N = cross(@N, up_vector);