[Plugin] triangulateFaces.rb v1.2 20101120

[thomthom]

@tig said:

Known Issues: Back Materials are kept, but these Texture UVs cannot be re-used;
there's a Ruby Console warning message if this problem is found...
Solution: use the front faces only for textures IF you might be triangulating later.

Why is it that you can't preserve the UVs of the backfaces?

[TIG]

We tried [CJP+me] but we couldn't get it to work - any ideas on fixing the whole issue of triangulation and keep UV mapping to front and back faces would be appreciated...

[thomthom]

hm... looking at the code:

mesh=face.mesh(1)
This will give you a PolygonMesh with only the FrontUV.

mesh=face.mesh(3) will give you front and back.
but you need to change this as well: uvs=mesh.uvs(true) true will give you set of front UVs, false will give you back UVs if you specified that in the .mesh method.

I'm not quite sure I understand the purpose of this:
outmesh = Geom::PolygonMesh.new faces.each{|f|outmesh.add_polygon(verts[f[0].abs-1],verts[f[1].abs-1],verts[f[2].abs-1])}
Why create a new PolygonMesh? Rearranging the polygons?

[TIG]

This was CJP's code...
I've messed on with your ideas but can only get the front OR back UVs to work... how do I get both ? Here's the re-jigged code so far...

def triangulateFace(face)
    mesh=face.mesh(3)
    verts=mesh.points
    ents=Sketchup.active_model.active_entities
    mat=face.material
    bac=face.back_material
    face.erase!
    grp=ents.add_group
    grp.entities.add_faces_from_mesh(mesh)
    grp.entities.each{|e|
        if e.class==Sketchup;;Edge
            e.smooth=false
            e.soft=false           
        elsif e.class==Sketchup;;Face
          uva=verts.index(e.vertices[0].position)
          uvb=verts.index(e.vertices[1].position)
          uvc=verts.index(e.vertices[2].position)
          if mat
            uvsF=mesh.uvs(true)
            e.position_material(mat, [verts[uva],uvsF[uva], verts[uvb],uvsF[uvb], verts[uvc],uvsF[uvc]], true)
          end#if
          if bac
            uvsB=mesh.uvs(false)
            e.position_material(bac,[verts[uva],uvsB[uva], verts[uvb],uvsB[uvb], verts[uvc],uvsB[uvc]], false)
          end#if
        end#if
    }
    grp.explode
end#def

[thomthom]

That bit of code seem to work.

[TIG]

@thomthom said:

That bit of code seem to work.

It does work for the back_material but it doesn't map the front material's uvs...
Try running it on a face with a hole in it and and materials front and back - both adjusted at angles/shear etc with Texture tool... Both materials are put back onto the now triangulated faces but the front material will be at its default settings...

I can't see how to do it

[thomthom]

Holes and sheared textures seems fine.

But, when I distort them, so the texture doesn't fit to a parallelogram, then it fails.
And that's excatly the conversation I've been having with Whaat a couple of days ago. That in order to sample textures which are distorted you need four points. Which leads to the question of PolygonMeshes: what do you do then, because if you just sample the UV from each point in the polygon you only get tree samples.

I wonder if PolygonMesh.uv_at(u,v) can be used though. The manual is not clear on this method. The description and example don't add up.

[TIG]

See what you mean - I had a distorted front face that failed...
if you have 4 ubs's how do we check ?

[TIG]

I have some thoughts...
The original face's mesh has a number of points - 3 or more.
A texture usually has 3 uvs 'points'.
A distorted texture has 4 uvs 'points'.
How do these uvs 'points' relate to the mesh points ? If you give them the equivalent 'index' then they'll work until index=3...
A face made from the mesh always has 3 points, these relate to the mesh points in sets of 3 - but how do these tie back to the texture uvs 'points' ? The fourth one index=3 fails ???
How do we make an array to place the material that has this fourth pair of a 3D point and a uvs 'point' ? It must reflect the 'extra point' somehow ??

I shall sleep on it and see if the little-grey-cells come up with anything...

[thomthom]

For my UV plugins I have used the UVHelper to sample the points. What I did then was sample four points of the face's place - completely ignoring the face's vertices.

Maybe, for each face that's turned into a PolygonMesh, sample four points of the front and back. Then once converted into PolygonMesh, apply the sampled UV points to each of the polygon faces. That should work. All the created polygon faces are still on the old face's plane.

[TIG]

More ideas... let me sleep... zzzzzzzzzzzzz x

[TIG]

def triangulateFace(face)
### if already a triangle leave alone...
 if face.vertices[3]
  mesh=face.mesh(3)
  ents=face.parent.entities
  mat=face.material
  bac=face.back_material
  ###
  p0=face.vertices[0].position
  p1=face.vertices[1].position
  p2=face.vertices[2].position
  p3=face.vertices[3].position
  ### get uvs
  tw=Sketchup.create_texture_writer
  uv_helperF=face.get_UVHelper(true,false,tw)
  uv_helperB=face.get_UVHelper(false,true,tw)
  uf0=uv_helperF.get_front_UVQ(p0)
  uf1=uv_helperF.get_front_UVQ(p1)
  uf2=uv_helperF.get_front_UVQ(p2)
  uf3=uv_helperF.get_front_UVQ(p3)
  ub0=uv_helperB.get_back_UVQ(p0)
  ub1=uv_helperB.get_back_UVQ(p1)
  ub2=uv_helperB.get_back_UVQ(p2)
  ub3=uv_helperB.get_back_UVQ(p3)
  ###
  grp=ents.add_group
  grp.entities.add_faces_from_mesh(mesh)
  grp.entities.each{|e|
    if e.class==Sketchup;;Edge
      e.smooth=false
      e.soft=false     
    elsif e.class==Sketchup;;Face
      if mat
        e.position_material(mat,[p0,uf0, p1,uf1, p2,uf2, p3,uf3], true)
      end#if
      if bac
        e.position_material(bac,[p0,ub0, p1,ub1, p2,ub2, p3,ub3], false)
      end#if
    end#if
  }
  face.erase!
  grp.explode
 end#if
end#def

Seems to me that this should work... but it doesn't - Thomthom, any ideas

[thomthom]

def triangulateFace(face)
### if already a triangle leave alone...
if face.vertices[3]
  mesh=face.mesh(3)
  ents=face.parent.entities
  mat=face.material
  bac=face.back_material
  ###
	# (TT)
	# Instead sampling vertices we sample points of the face's plane.
	# This is because we need four points, and some times a face only has tree vertices.
	# And we also get the wrong result if any of the first four vertices are co-linear.
	samples = []
	samples << face.vertices[0].position			 # 0,0 | Origin
	samples << samples[0].offset(face.normal.axes.x) # 1,0 | Offset Origin in X
	samples << samples[0].offset(face.normal.axes.y) # 0,1 | Offset Origin in Y
	samples << samples[1].offset(face.normal.axes.y) # 1,1 | Offset X in Y
  ### get uvs
  tw=Sketchup.create_texture_writer
	# (TT)
	uv_helper=face.get_UVHelper(true,true,tw) # (TT) Only need one UV Helper
	xyz = []
	uv_f = []
	uv_b = []
	samples.each { |position|
		# XYZ 3D coordinates
		xyz << position
		# UV 2D coordinates
		# Front
		uvq = uv_helper.get_front_UVQ(position)
		uv_f << flattenUVQ(uvq)
		# Back
		uvq = uv_helper.get_back_UVQ(position)
		uv_b << flattenUVQ(uvq)
	}
  ###
  grp=ents.add_group
  grp.entities.fill_from_mesh(mesh, true, 0) # (TT) Adds the mesh without soft/smooth edges. (and faster)
  grp.entities.each{|e|
    next unless e.class==Sketchup;;Face
      if mat
		# (TT)
		# Position texture.
		pts = []
		(0..3).each { |i|
			pts << xyz[i]
			pts << uv_f[i]
		}
        e.position_material(mat,pts, true)
      end#if
      if bac
		# (TT)
		# Position texture.
		pts = []
		(0..3).each { |i|
			pts << xyz[i]
			pts << uv_b[i]
		}
        e.position_material(bac,pts, false)
      end#if
  }
  face.erase!
  grp.explode
end#if
end#def
# (TT)
# Get UV coordinates from UVQ matrix.
def flattenUVQ(uvq)
	return Geom;;Point3d.new(uvq.x / uvq.z, uvq.y / uvq.z, 1.0)
end

[TIG]

Thanks to CPhillips's inciteful ideas I have now made a 'joint' script called 'triangulateFaces.rb' which is attached. It uses CPhillips's triangulateFace(face) code [with a slight TIG addition for back_materials] and the TIG Plugin triangulateFaces(face_array)...
Originally 2009 (c) CPhillips* then (c) TIG** THEN (c) ThomThom ***
Script: triangulateFaces.rb
Code Usage: triangulateFace(face)*
Result: it triangulates a face... all Texture UVs are kept.
Plugin Usage: triangulateFaces(faces_array)**
Result: it triangulates faces in a selection...
v1.0
First Release: Def Code 'mesh' idea by CPhillips*,
retained back_materials added by TIG [failed] ###,
Plugin parts by TIG**. 20090729
v1.1
Rewritten entirely by TIG... THEN completely corrected by Thomthom (TT)!***
It now retains all Texture mapping successfully. 20091203
v1.2
Triangulated faces with 4 sides glitch fixed using intersection.
Get the latest version from here http://sketchucation.com/pluginstore?pln=triangulateFaces

[TIG]

Here's v1.1 http://forums.sketchucation.com/viewtopic.php?p=175613#p175613

Thanks to Thomtom's knowledge of uvs mapping etc it now successfully triangulates any face [even with holes like Swiss Cheese] and keeps the front AND back uv texture mapping as it was ! Thanks!

[Gaieus]

Hi TIG,

Would it be possible for the plugin to triangulate faces with a more "even" or "regular" triangles? After this topic, I thought maybe pre-triangulating the face on the ramp would spare some extra hand-work but it seems that the plugin triangulates the faces just exactly the same way native SU does when autofolding.

---

---

TriangulateFaces.skp

[TIG]

@gaieus said:

Hi TIG,
Would it be possible for the plugin to triangulate faces with a more "even" or "regular" triangles? After this topic, I thought maybe pre-triangulating the face on the ramp would spare some extra hand-work but it seems that the plugin triangulates the faces just exactly the same way native SU does when autofolding.

TriangulateFaces uses the built-in SUp mesh making methods, which presumably match the auto-fold ones, hence the similarity.
You might have noticed that my ExtendEdgesByRails script does produce a neat set of faces as that can't use the mesh methods directly but has to make up its own...
Using EEbyRails is a MUCH simpler way of making a curved ramp - I've attached an example...EEbyRailsSimpleRamp.skp

[Gaieus]

Thanks TIG for the examples - although my question was more a bit "academical" and theoretical - but at least I know why the two meshes are similar.

Certainly the other twoo tools are also great and would probably fit more to this particular need - that moving of the face was just so simple method - too bad autofold screws it up.

[thomthom]

@gaieus said:

Certainly the other twoo tools are also great and would probably fit more to this particular need - that moving of the face was just so simple method - too bad autofold screws it up.

This triangulation would be a separate plugin. It's just too specific. But I've been thinking of this myself. I often find I want such partitioning. It seems that it's usually long strip of a face where two of the sides runs parallel-ish to each other. So you want an edge to go between each opposite vertex. I've had it on my list of things to do - just not got around to it yet.

[alz]

Yeah, I agree -- having a more uniform triangulation method is preferred. It makes things a lot easier developing models if it's more uniformed and less "meet all at one point".

With the current method, I have to spend time flip-flopping various divisions (and sometimes just recutting the face).