Calculating the final vertices of a nested face

[shotgunefx]

I've tried to boil this down to a small as example as possible, what I need to do is given a face, calculate it's absolute final position in XYZ (taking into account transforms, etc). It's for a paint tool I'm working on that works (and aligns regardless of grouping. I happen to use Sketchup for game mapping and the particulars of the exporter force pretty much everything to be a group.

A less than compelling example video of the paint tool http://www.youtube.com/watch?v=hb63D7Cmt50

I've mostly got it working, except for the origin is off when dealing with groups within groups, there is just something I'm not grokking here. So after many hours of head scratching, I figured I'd see if anyone can enlighten me.

So I take the face, I walk up the hierarchy, adding transforms, (and in theory, transformation origins) and compute the new points. The code below just adds the transformation.origin, I know this is wrong, and it's what trying to solve. I've tried a dozen things (transforming them by the container, etc,) but there is just something I'm not understanding.

Here's the code

module WALK

def WALK.setface
    model = Sketchup.active_model
    @newg = model.entities.add_group
    @s = nil
    if model.selection.empty?
        UI.messagebox "Selection empty"
        return nil
    else
        if model.selection[0].is_a? Sketchup;;Face
            @s = model.selection[0]
        else 
            UI.messagebox "Face not selected"
        end 
    end
end

# make sure groups are unique
Sketchup.active_model.definitions.each{|d|d.instances[1..-1].each{|i|i.make_unique}if d.group? and d.instances[1]}
 
def WALK.main
     WALK.GetParent(@s)
end

def WALK.GetParent(ent)
   Sketchup.active_model.start_operation("Walk")
   model = Sketchup.active_model
   @newg = model.entities.add_group
   m = model.materials.add "test"
   m.color="red"
   orig = ent
   tpos = Geom;;Point3d.new 0,0,0  # keep track of origin
   trans = Geom;;Transformation.new(Geom;;Point3d.new(0,0,0))    # add transforms to this
   
   while (ent.respond_to?('parent') )   # walk up hierarchy
        if ((ent.is_a? Sketchup;;ComponentDefinition))
            if ent.group?
                t = ent.instances[0].transformation # Get the group's transform
                tpos += t.origin.transform(trans).to_a  # !!!WRONG
                trans *= t  # combine transforms
            end     
            ent =  ent.instances[0]     # become the instance
        end
        ent = ent.parent
   end
   vertices = orig.outer_loop.vertices
   newverts = []
   vertices.each do |v|
        np = v.position.clone
        np+= tpos.to_a      # !!! Wrong
        np.transform! trans
        newverts.push  np
    end   
   f = @newg.entities.add_face newverts    # create the face
   f.material=m
   Sketchup.active_model.commit_operation
end   
end # end mod
if !file_loaded?(__FILE__)
  UI.menu("Plugins").add_item("Select Walk Face") { WALK.setface }
  UI.menu("Plugins").add_item("Make Walk Face") { WALK.main }
end

file_loaded(__FILE__)

It adds two items to the plugin menu
Select Walk Face and Make Walk Face

Take the example here

The geom looks like this...
Group
--Group
----Wide Cylinder faces
--Group
----Group
------Cube faces
----Group
------ Tall Cylinder Faces

Seeing backing out of a group clears the selection, here's where Select Walk Face comes in. Click down into the inner group of the cube and select a face and then select Select Walk Face, this simply stashes the face for Make Walk Face

Now if you actually ran Make Walk Face here, it works fine, making a new face, respecting transforms and in the right place.

But back all the way out of the group and run Make Walk Face

and you get this....

If you've read this far, I commend you

Any insight on what I'm not understanding would truly be appreciated.

Thanks!
-Lee

[TIG]

Have you tried tr=container.transformation.inverse and applying it to the initial object and then iterating and getting/setting the transformation for the container's container etc until you get to the model level...

[shotgunefx]

@tig said:

Have you tried tr=container.transformation.inverse and applying it to the initial object and then iterating and getting/setting the transformation for the container's container etc until you get to the model level...

That didn't seem to work (inverse), though I may very well have misunderstood what you meant, but what you said gave me an answer anyway. By applying the transform to the points at each container successively, it works perfectly! (or at least in every test so far)

Which is how I should have tried it initially but I was thinking from a performance standpoint, and forgot the old adage "premature optimization is the root of all evil"

def WALK.GetParent(ent)
   Sketchup.active_model.start_operation("Walk")
   model = Sketchup.active_model
   @newg = model.entities.add_group
   m = model.materials.add "test"
   m.color="red"
   orig = ent
   tpos = Geom;;Point3d.new 0,0,0  # keep track of origin
   trans = Geom;;Transformation.new(Geom;;Point3d.new(0,0,0))    # add transforms to this

   vertices = orig.outer_loop.vertices.map {|v| v.position.clone}
   
   while (ent.respond_to?('parent') )   # walk up hierarchy
        if ((ent.is_a? Sketchup;;ComponentDefinition))
            if ent.group?
                t = ent.instances[0].transformation # Get the group's transform
                vertices.each_with_index do |v,i|
                    vertices[i].transform! t 
                end
            end     
            ent =  ent.instances[0]     # become the instance
        end
        ent = ent.parent
   end
   f = @newg.entities.add_face vertices    # create the face
   f.material=m
   Sketchup.active_model.commit_operation
end   

Thanks again for the help!