[Plugin] triangulateFaces.rb v1.2 20101120

TIG

@tig said:

@cphillips said:

I needed the triangulation to prepare a model for export.

Thanks for incorporating it into your script TIG! Why is it that back facing UV's didn't work?

There is only a method to 'place material textures on a face' - and that assumes a 'front_face' - there's no 'back_face' method...

Do you mean position_material? It takes a bool for front or back material

http://code.google.com/apis/sketchup/docs/ourdoc/face.html#position_material

Duh! I'll adjust the code and re-post...

TIG

There's something afoot... What I posted before worked - on keeping the front face texture mapping but not on the back_face... Now when I try it it fails to map both faces ? Any ideas - CPhillips's idea worked fine in tests but now seems to fail...

CPhillips

Post the code and I'll have a look. It might be the face.mesh(1). I think you need to use a different number when you want back uv's as well.

honoluludesktop

Hi TIG, Any way to convert this kind of mesh into its component triangles?

Drapery05.skp

TIG

@honoluludesktop said:

Hi TIG, Any way to convert this kind of mesh into its component triangles?

I wrote an example script a few weeks ago to do something like this... http://forums.sketchucation.com/viewtopic.php?p=186068#p186068

honoluludesktop

TIG, Thanks for the link, it works. Now I can make small edits to the (mesh?).

jeff hammond

@tig said:

Result: it triangulates a face... front Texture UVs are kept.

hey TIG,

if i run the script on this sphere, the UVs go haywire.
am i misunderstanding or misusing the script?
thanks

[edit] ok, wait.. i just read the rest of the thread and i guess this hasn't been sorted out ?

sorry about the size.. i guess i could of used a smaller texture

TIG

@unknownuser said:

@tig said:

Result: it triangulates a face... front Texture UVs are kept.

hey TIG,

if i run the script on this sphere, the UVs go haywire.
am i misunderstanding or misusing the script?
thanks

[edit] ok, wait.. i just read the rest of the thread and i guess this hasn't been sorted out ?

It's broken... the UV mapping was CJP's but it still needs fixing...

jeff hammond

@tig said:

It's broken... the UV mapping was CJP's but it still needs fixing...

ah, ok..
too bad

[fwiw - i can manually triangulate the sphere using and everything turns out ok.. i guess this script is doing something other than just drawing lines to cut quads in half?]

TIG

@unknownuser said:

@tig said:

It's broken... the UV mapping was CJP's but it still needs fixing...

ah, ok..
too bad

[fwiw - i can manually triangulate the sphere using and everything turns out ok.. i guess this script is doing something other than just drawing lines to cut quads in half?]

It triangulates the quads and tries to fix the UV mapping - obviously very badly !!!! CJP help!

TIG

See this new script just for selected quad faces - it keeps UV mapping etc...
http://forums.sketchucation.com/viewtopic.php?p=201025#p201025

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...