Fit_plane_to_points problem

dacastror

Hi guys, I'm trying to adjust hundreds of points to a plane, my problem is that I do not understand the output format fit_plane_to_points, I expected a Point3d and Vector3D, but it seems I get different, I do not know how to interpret the result, appreciate the help in advance

point1 = Geom::Point3d.new 0,0,0 point2 = Geom::Point3d.new 1,2,3 point3 = Geom::Point3d.new 5,5,5 plane = Geom.fit_plane_to_points point1, point2, point3 plane.size

Dan Rathbun

The plane is returned as an [A,B,C,D] Array of 4 numbers which are the coefficients of the plane equation Ax + By + Cz + D = 0.

jolran

Fit plane to Points returns a plane on which you can use SU-API methods.
It also returns what Dan said.

A plane is infinite, and so is a Line [point3d, vector]

I suspect what you acctually want to do is Project your Points on to that plane with the point.project_to_plane method?

dacastror

thank you very much Dan, is exactly what I needed

thank jolran, that's not my next step, but I thank you, I had not seen the command project_to_plane

dacastror

I thought of a way to put the plane in the format [point, vector], at some point it might be useful to someone

p1 = Geom;;Point3d.new 1,1,1
p2 = Geom;;Point3d.new 2,1,1
p3 = Geom;;Point3d.new 1,2,1
p4 = Geom;;Point3d.new 1,2,0
pl = Geom.fit_plane_to_points p1, p2, p3, p4

tolerance = 0.0001
if pl[2].abs > tolerance
   point = Geom;;Point3d.new(0,0,-pl[3]/ pl[2])
elsif pl[1].abs > tolerance
   point = Geom;;Point3d.new(0,-pl[3]/ pl[1],0)
else
   point = Geom;;Point3d.new(-pl[3]/ pl[0],0,0)
end
vector = Geom;;Vector3d.new(pl[0],pl[1],pl[2])

plane = [point,vector]

jolran

@unknownuser said:

thank jolran, that's not my next step, but I thank you, I had not seen the command project_to_plane

Ahh, I see. You ARE just interested in getting Point and vector, for some reason.

Then if I'm not misstaken I think p4 is redudant in you calculation ?

You only have to feed 3 Points for fit_plane_to_points.

thomthom

https://bitbucket.org/thomthom/tt-library-2/src/2bb264f27d9bc00c1b1f9a969e481c19385042ad/TT_Lib2/geom3d.rb?at=Version%202.9#cl-20

<span class="syntaxdefault">&nbsp;&nbsp;</span><span class="syntaxcomment">#&nbsp;Returns&nbsp;+plane+&nbsp;in&nbsp;the&nbsp;format&nbsp;+[&nbsp;point3d,&nbsp;vector3d&nbsp;]+.<br />&nbsp;&nbsp;#<br />&nbsp;&nbsp;#&nbsp;@param&nbsp;[Array<Geom;;Point3d,&nbsp;Geom;;Vector3d>,&nbsp;Array<Number,&nbsp;Number,&nbsp;Number,&nbsp;Number>]&nbsp;plane<br />&nbsp;&nbsp;#<br />&nbsp;&nbsp;#&nbsp;@return&nbsp;[Array<Geom;;Point3d,&nbsp;Geom;;Vector3d>]<br />&nbsp;&nbsp;#&nbsp;@since&nbsp;2.0.0<br />&nbsp;&nbsp;</span><span class="syntaxdefault">def&nbsp;self</span><span class="syntaxkeyword">.</span><span class="syntaxdefault">normalize_plane</span><span class="syntaxkeyword">(</span><span class="syntaxdefault">plane</span><span class="syntaxkeyword">)<br />&nbsp;&nbsp;&nbsp;&nbsp;return&nbsp;</span><span class="syntaxdefault">plane&nbsp;</span><span class="syntaxkeyword">if&nbsp;</span><span class="syntaxdefault">plane</span><span class="syntaxkeyword">.</span><span class="syntaxdefault">length&nbsp;</span><span class="syntaxkeyword">==&nbsp;</span><span class="syntaxdefault">2<br />&nbsp;&nbsp;&nbsp;&nbsp;a</span><span class="syntaxkeyword">,&nbsp;</span><span class="syntaxdefault">b</span><span class="syntaxkeyword">,&nbsp;</span><span class="syntaxdefault">c</span><span class="syntaxkeyword">,&nbsp;</span><span class="syntaxdefault">d&nbsp;</span><span class="syntaxkeyword">=&nbsp;</span><span class="syntaxdefault">plane<br />&nbsp;&nbsp;&nbsp;&nbsp;v&nbsp;</span><span class="syntaxkeyword">=&nbsp;</span><span class="syntaxdefault">Geom</span><span class="syntaxkeyword">;;</span><span class="syntaxdefault">Vector3d</span><span class="syntaxkeyword">.new(</span><span class="syntaxdefault">a</span><span class="syntaxkeyword">,</span><span class="syntaxdefault">b</span><span class="syntaxkeyword">,</span><span class="syntaxdefault">c</span><span class="syntaxkeyword">)<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span class="syntaxdefault">p&nbsp;</span><span class="syntaxkeyword">=&nbsp;</span><span class="syntaxdefault">ORIGIN</span><span class="syntaxkeyword">.</span><span class="syntaxdefault">offset</span><span class="syntaxkeyword">(</span><span class="syntaxdefault">v</span><span class="syntaxkeyword">.</span><span class="syntaxdefault">reverse</span><span class="syntaxkeyword">,&nbsp;</span><span class="syntaxdefault">d</span><span class="syntaxkeyword">)<br />&nbsp;&nbsp;&nbsp;&nbsp;return&nbsp;[</span><span class="syntaxdefault">p</span><span class="syntaxkeyword">,&nbsp;</span><span class="syntaxdefault">v</span><span class="syntaxkeyword">]<br />&nbsp;&nbsp;</span><span class="syntaxdefault">end<br /></span>

thomthom

@dacastror said:

I expected a Point3d and Vector3D, but it seems I get different,

The definition of a plane in SketchUp is described in the introduction to Geom3d: sketchucation.com/forums/posting.php?mode=quote&f=180&p=485589

@unknownuser said:

A line can be represented as either an Array of a point and a vector, or as an Array of two points.

<span class="syntaxdefault">     line </span><span class="syntaxkeyword">=</span><span class="syntaxdefault"> </span><span class="syntaxkeyword">[</span><span class="syntaxdefault">Geom</span><span class="syntaxkeyword">;;</span><span class="syntaxdefault">Point3d</span><span class="syntaxkeyword">.new(</span><span class="syntaxdefault">0</span><span class="syntaxkeyword">,</span><span class="syntaxdefault">0</span><span class="syntaxkeyword">,</span><span class="syntaxdefault">0</span><span class="syntaxkeyword">),<br /></span><span class="syntaxdefault">     Geom</span><span class="syntaxkeyword">;;</span><span class="syntaxdefault">Vector3d</span><span class="syntaxkeyword">.new(</span><span class="syntaxdefault">0</span><span class="syntaxkeyword">,</span><span class="syntaxdefault">0</span><span class="syntaxkeyword">,</span><span class="syntaxdefault">1</span><span class="syntaxkeyword">)]<br /></span><span class="syntaxdefault">     line </span><span class="syntaxkeyword">=</span><span class="syntaxdefault"> </span><span class="syntaxkeyword">[</span><span class="syntaxdefault">Geom</span><span class="syntaxkeyword">;;</span><span class="syntaxdefault">Point3d</span><span class="syntaxkeyword">.new(</span><span class="syntaxdefault">0</span><span class="syntaxkeyword">,</span><span class="syntaxdefault">0</span><span class="syntaxkeyword">,</span><span class="syntaxdefault">0</span><span class="syntaxkeyword">),<br /></span><span class="syntaxdefault">     Geom</span><span class="syntaxkeyword">;;</span><span class="syntaxdefault">Point3d</span><span class="syntaxkeyword">.new(</span><span class="syntaxdefault">0</span><span class="syntaxkeyword">,</span><span class="syntaxdefault">0</span><span class="syntaxkeyword">,</span><span class="syntaxdefault">100</span><span class="syntaxkeyword">)]</span><span class="syntaxdefault"> </span>

A plane can be represented as either an Array of a point and a vector, or as an Array of 4 numbers that give the coefficients of a plane equation.

<span class="syntaxdefault">     plane </span><span class="syntaxkeyword">=</span><span class="syntaxdefault"> </span><span class="syntaxkeyword">[</span><span class="syntaxdefault">Geom</span><span class="syntaxkeyword">;;</span><span class="syntaxdefault">Point3d</span><span class="syntaxkeyword">.new(</span><span class="syntaxdefault">0</span><span class="syntaxkeyword">,</span><span class="syntaxdefault">0</span><span class="syntaxkeyword">,</span><span class="syntaxdefault">0</span><span class="syntaxkeyword">),<br /></span><span class="syntaxdefault">     Geom</span><span class="syntaxkeyword">;;</span><span class="syntaxdefault">Vector3d</span><span class="syntaxkeyword">.new(</span><span class="syntaxdefault">0</span><span class="syntaxkeyword">,</span><span class="syntaxdefault">0</span><span class="syntaxkeyword">,</span><span class="syntaxdefault">1</span><span class="syntaxkeyword">)]<br /></span><span class="syntaxdefault">     plane </span><span class="syntaxkeyword">=</span><span class="syntaxdefault"> </span><span class="syntaxkeyword">[</span><span class="syntaxdefault">0</span><span class="syntaxkeyword">,</span><span class="syntaxdefault">0</span><span class="syntaxkeyword">,</span><span class="syntaxdefault">1</span><span class="syntaxkeyword">,</span><span class="syntaxdefault">0</span><span class="syntaxkeyword">]</span><span class="syntaxdefault"> </span>

dacastror

I did not understand point.offset, with this example I understand a little more, thank you very much Thom, very interesting this