Intersect_with question/problem

th3lurker

So after another long deliberation i chose to use the add_faces_from_mesh or fill_from_mesh for that export i keep blabbering about. Sadly this creates a few problems, one of which is that i can't position textures directly, i have to go through the whole newly created faces list and position the texture on each of them. For that i have to keep track of the order in which the faces are added, cause there is no way to associate the polygon created for the mesh object with the face object generated when i create the mesh, except to remember the order in which they were created.
The second problem i have, and the one i have questions about is cutting a hole. Seems easy, doesn't it? Well the mesh object google provides doesn't allow us to specify the "inner loops", unlike the unsupported C++ SDK. One option would be to use the usual add_face method, folled by add_face + erase for the holes. That slows down the export, so i have to try and find a different way. One way would be to add the faces from the mesh and then delete the holes. Thing is, if i add 2 polygons, let's say 2 squares, one smaller, inside the other one, no common points, when i create the mesh the two faces created overlap, but do not intersect, so deleting the smaller one makes no difference. Here i get to the intersect_with problem. I can't get it to work. Since i can't post from work (our ISP's IPs are all banned for some reason) i'll try and write the code from memory.

model = Sketchup.active_model
entities = model.active_entities

pt1 = Geom;;Point3d.new 0,0,0
pt2 = Geom;;Point3d.new 10,0,0
pt3 = Geom;;Point3d.new 10,10,0
pt4 = Geom;;Point3d.new 0,10,0
pt5 = Geom;;Point3d.new 1,1,0
pt6 = Geom;;Point3d.new 9,1,0
pt7 = Geom;;Point3d.new 9,9,0
pt8 = Geom;;Point3d.new 1,9,0

mesh = Geom;;PolygonMesh.new
mesh.add_polygon pt1,pt2,pt3,pt4
mesh.add_polygon pt5,pt6,pt7,pt8

group = entities.add_group
group.entities.add_faces_from_mesh mesh,0
#now i have to try and intersect the faces, actually i have to #intersect the 4 lines that make up the smaller square with the #face that is the larger square
transformation = group.transform! #i forgot the exclamation #point at work....hmmmm
#now if i provide the last parameter as an array of entities i #extract from group.entities, it crashes if i provide one or more #line objects in the list. if i only provide face object it #doesn't crash, but doesn't do anything either
entityArray = Array.new
entityArray.push group.entities[i] #with i i can select the lines 0-3,5-8 or the faces 4,9, i won't write that code
entities.intersect_with true, transformation, group.entities, transformation, true, entityArray

What am i doing wrong?

TIG

transformation = group.transformation
...
entityArray=group.entities.to_a
...

TIG

Let's assume that 'world' and 'holeface' intersect each other...
Then you still need to do a 'intersect_with' the 'world' and 'holeface' meshes.
Then the 'holeface' deletion would still leave the edges of the faces.
You can get a references to these as say...
togos=[]
holeface.each{|face|
face.edges.each{|e|
togos << e if e.faces.length==1
}
}
then use ...entities_erase(togos)
AND worse it leaves extra faces if some are split... you can collect these by making an array of faces before the intersect_with and then an array afterwards.
You then need to test this list to see it any of the 'new' faces need deleting - e.g. if they share planartity with those in the 'world' mesh maybe not???

I see this as a flawed approach

Dan Rathbun

TIG may know the answer to this...

What if you create 2 mesh objects .. "the world" and another for "the hole" ...

Then:
gents = group.entities gents.add_faces_from_mesh( mesh1 ) holeface = gents.add_faces_from_mesh( mesh2 ) gents.erase_entities( holeface )

??

EDIT: Wont work because the dang API docs are wrong! .. again.
add_faces_from_mesh() returns a Fixnum integer, not an array of the faces added.

Dan Rathbun

Success

I let the explode do the intersect ...

model = Sketchup.active_model
ents = model.active_entities
 
pt1 = Geom;;Point3d.new 0,0,0
pt2 = Geom;;Point3d.new 10,0,0
pt3 = Geom;;Point3d.new 10,10,0
pt4 = Geom;;Point3d.new 0,10,0
pt5 = Geom;;Point3d.new 1,1,0
pt6 = Geom;;Point3d.new 9,1,0
pt7 = Geom;;Point3d.new 9,9,0
pt8 = Geom;;Point3d.new 1,9,0
 
mesh1 = Geom;;PolygonMesh.new
mesh1.add_polygon pt1,pt2,pt3,pt4

mesh2 = Geom;;PolygonMesh.new
mesh2.add_polygon pt5,pt6,pt7,pt8

grp = ents.add_group
gents = grp.entities
gents.add_faces_from_mesh( mesh1 )

grp2 = gents.add_group # nested group
grp2.entities.add_faces_from_mesh( mesh2 )
#
holeface = grp2.entities.to_a.find_all{|e| e.is_a?(Sketchup;;Face)}
grp2.entities.erase_entities( holeface )
holeface = nil # so it's not pointing at a deleted entity
holeloop = grp2.entities.to_a

grp2.explode # merge with parent group
togo = []
grp.entities.to_a.each{|e|
  if e.is_a?(Sketchup;;Face) &&
         e.edges == holeloop
    togo << e
  end
}
grp.entities.erase_entities( togo )
grp2 = togo = nil # GC