I've been looking for an answer to this question for quite some time, but in the end it turned out easier than I thought. I've defined 3 points (P1, P2 and P3) in space that I want to lay flat (i.e. parallel to the X - Y plane). Firstly, I translate P1 to the origin so I get what I described in the question, then I take the cross-product of the two other (translated) points, en determine the spherical coordinates of the endpoint of this product. Then 2 rotations will rotate this vector to make it point in the direction of the Z-axis. The rotated points P1', P2' and P3' are not in the X - Y plane, but that is no problem, the slicer will fix that. Maurice P1=[1,2,3]; P2=[3,4,5]; P3=[-5,6,1]; D=.3; hull(){ // original plane translate(P1) sphere(D); translate(P2) sphere(D); translate(P3) sphere(D); } P12=P2-P1; // translate P1 to origin P13=P3-P1; Cr=cross(P12,P13); // calculate cross product R=norm(Cr); // calculate spherical coordinates Inclin=acos(Cr.z/R); Azim=atan2(Cr.y,Cr.x); rotate([0,-Inclin,0]) // and rotate accodingly rotate([0,0,-Azim]) color("Red") hull(){ // rotated plane translate(P1) sphere(D); translate(P2) sphere(D); translate(P3) sphere(D); } >Hi, > >A plane is defined by O, X (x1,x2,x3) and Y (y1,y2,y3). What is the >(simplest) way to rotate this plane so that O stays O and both X and >Y rotate to the x, y plane (immaterial where)? > >I want to lay an object flat on my printer table, and Cura refuses >to do it unfortunately... > >Thanks, >Maurice