Issues with a simple material copy raycast script

TIG · 7 Sept 2018, 23:03

In your image face_below is the 'source' face [the inverse of my assumptions].
And therefore face_above is the 'target', so your code needs to swap them to suit.
AND the ' raytest' then needs to follow Z_AXIS.reverse, so it look up NOT down...

BOTH will work, BUT just be consistent...

chanz · 7 Sept 2018, 23:30

@tig said:

In your image face_below is the 'source' face [the inverse of my assumptions].
And therefore face_above is the 'target', so your code needs to swap them to suit.
AND the ' raytest' then needs to follow Z_AXIS.reverse, so it look up NOT down...

BOTH will work, BUT just be consistent...

Exactly. So we are raytesting from face_above downwards to face_below (the source) to get the materials and UV. Apologies for the confusion.

This still has no effect on the UVs though, which are still not working. I have attached the script with the above agreed upon naming convention and additional clarifying comments. Try it in the test scene if you get a chance. Thanks TIG.

Fixed naming conventions

TIG · 9 Sept 2018, 18:04

So your convention is upper surface has 'no-material', lower surface has 'textures'.
Unless you known the two meshes have identical faces you can't safely tale a point on an upper facet and project down and be sure of hitting a lower facet...
But for now let's assume all goes well and we have 'hits', how are you going to get the lower facet's texture ?
Isn't it better to process each lower textured facet, and project upwards to get a matching upper facet.
You then need to get the UV mapping for the lower facet, and apply it to the lower facet's material which is applied onto the equivalent upper facet.

Just think about which is which...

chanz · 9 Sept 2018, 18:23

@tig said:

So your convention is upper surface has 'no-material', lower surface has 'textures'.
Unless you known the two meshes have identical faces you can't safely tale a point on an upper facet and project down and be sure of hitting a lower facet...
But for now let's assume all goes well and we have 'hits', how are you going to get the lower facet's texture ?
Isn't it better to process each lower textured facet, and project upwards to get a matching upper facet.
You then need to get the UV mapping for the lower facet, and apply it to the lower facet's material which is applied onto the equivalent upper facet.

Just think about which is which...

It really doesn't matter to me which direction is taken. I'm absolutely fine using the method you suggest where we raycast up applying the material and UVs from the raycast source face to the hit face. Works for me.

I think your edits to my script were doing just that. But I got the same results as mine where the UVs were messed up

Thinking about it, because I'm using drop vertices and the meshes are nearly identical but not perfectly the same, could that be causing issues with the UVs? Perhaps that's the issue where it copies it just fine but because the faces differ, we get issues.

So if that's the case, the next questions is how difficult it would be to modify drop vertices to preserve the UVs when it drops. Vertex Tools has a similar feature where you can lock the UVs.

Would that be an easier approach?

Thanks as always, TIG.

TIG · 9 Sept 2018, 19:47

In my earlier version, if I make the to textured and project it onto a lower surface the top one's UV mapping is repeated on the lower surface.
So I know it works.
You just need to swap top/bottom properly to apply to you own chosen set up...

If you use a blank face's UV mapping you won't get what's on the UV-mapped face...

Try it with just a few facets first...

chanz · 9 Sept 2018, 19:57

@tig said:

In my earlier version, if I make the to textured and project it onto a lower surface the top one's UV mapping is repeated on the lower surface.
So I know it works.
You just need to swap top/bottom properly to apply to you own chosen set up...

If you use a blank face's UV mapping you won't get what's on the UV-mapped face...

Try it with just a few facets first...

Maybe I'm having trouble understanding. I'll use the script you posted and the test model I posted. What was your exact process to get the UVs on the top model looking like the original on the bottom? Maybe our process is just different. I assumed you used the test model I uploaded?

TIG · 9 Sept 2018, 20:18

I can see some issues, BUT you need to clarify what face's texture you are copying with UVs and onto which face you apply them...

chanz · 9 Sept 2018, 20:30

@tig said:

I can see some issues, BUT you need to clarify what face's texture you are copying with UVs and onto which face you apply them...

Maybe I'm just explaining it wrong, but I don't know how to be more clear about what I'm after. I have uploaded a few pictures about what I'm after as well as a model which allows me to test.

In the model I have the original on the bottom and the recreated mesh on the top. I want the textures and UVs of the faces on the bottom to be copied to the untextured model above.

Sorry. Maybe I'm just misunderstanding what you're asking.

Thanks for being patient.

TIG · 10 Sept 2018, 12:09

I think this code does what you want.

I have used your original conventions...
The upper faces are the un-textured ones and the lower faces are textured.
Each of the upper faces centroids now casts a ray downwards, and if it hits a lower face then the material from the lower face is applied onto the upper face, using the lower face's UV mapping.
We can't be 100% sure that the ray will always hit a face below, because the upper and lower faces are different shapes etc, so if the ray hits a lower edge rather than a lower face, then there's no face to get a material from - so in that case a lower face belonging to that lower edge is found and used in lieu - that way we never have a 'blank' face in the upper set.
Because the faces differ in some places the UV mapping can look a little odd on occasion...

### CopyBelowMaterials.rb
### by Chanz
require 'sketchup.rb'
###
module DAN
  ###
  def self.copymaterials()
    model=Sketchup.active_model
    ents=model.active_entities
    #ss=model.selection ### use selected UNtextured [upper] faces to speed it up
    faces = ents.grep(Sketchup;;Face)
    #faces = ss.grep(Sketchup;;Face) ### use selected UNtextured faces to speed it up
    ###
    return nil unless faces[0]
    ###
    begin
      model.start_operation("DAN.copymaterials", true)
    rescue
      model.start_operation("DAN.copymaterials")
    end
    ###
    faces.each {|face|
      rayt = model.raytest(c=self.find_centroid(face), Z_AXIS.reverse)
			### UPPER >>> LOWER
      if rayt
        f = rayt[1].grep(Sketchup;;Face)[0]
				unless f
				  f = nil
				  e = rayt[1].grep(Sketchup;;Edge)
					f = e[0].faces[0] if e
				end
				self.process_face(face, f) if f ### UPPER >>> LOWER
      end
    }
    ###
    model.commit_operation
    ###
  end

  # Finds an adjusted point, so we won't raycast down to an edge ;) HOPEFULLY
  ### OK if triangulated...
  ### BUT IF the face is L shaped the centroid might not fall on it !!!
  def self.find_centroid(face)
    vertices=face.vertices
    vertices[vertices.length]=vertices[0]
    centroid=Geom;;Point3d.new()
    a_sum=0.0
    y_sum=0.0
    x_sum=0.0
    for i in (0...vertices.length-1)
      temp=(vertices[i].position.x*vertices[i+1].position.y)-(vertices[i+1].position.x*vertices[i].position.y)
      a_sum+=temp
      x_sum+=(vertices[i+1].position.x+vertices[i].position.x)*temp
      y_sum+=(vertices[i+1].position.y+vertices[i].position.y)*temp
    end###for
    centroid.x=x_sum/(3*a_sum)
    centroid.y=y_sum/(3*a_sum)
    centroid.z=face.bounds.min.z
    return centroid
  end
 
  # NOTE; face_upper is in the model.ents||selection, face_lower is the TEXTURED face the raytest hit
  def self.process_face(face_upper, face_lower)
    ###
    texture_writer=Sketchup.create_texture_writer
    ###
    if face_lower.material && ! face_lower.material.texture
      ### paint the plain material if it exists but it has no texture
      face_upper.material=face_lower.material
    elsif face_lower.material ### A material and it has a texture...
      # Sample the UVs from LOWER face
      samples = []
      samples << face_lower.vertices[0].position             ### 0,0 | Origin
      samples << samples[0].offset(face_lower.normal.axes.x) ### 1,0 | Offset Origin in X
      samples << samples[0].offset(face_lower.normal.axes.y) ### 0,1 | Offset Origin in Y
      samples << samples[1].offset(face_lower.normal.axes.y) ### 1,1 | Offset X in Y
      xyz = [];uv = [] ### Arrays containing 3D and UV points.
      uvh = face_lower.get_UVHelper(true, true, texture_writer)
      samples.each { |position|
        xyz << position ### XYZ 3D coordinates
        uvq = uvh.get_front_UVQ(position) ### UV 2D coordinates
        uv << self.flattenUVQ(uvq)
      }
      pts = [] ### Position texture.
      (0..3).each { |i|
        pts << xyz[i]
        pts << uv[i]
      }
      # Set the position for textured material from face_upper onto face_lower front
      face_upper.position_material(face_lower.material, pts, true)
    end
    ###
  end
 
  ### Get UV coordinates from UVQ matrix.
  def self.flattenUVQ(uvq)
    return Geom;;Point3d.new(uvq.x / uvq.z, uvq.y / uvq.z, 1.0)
  end
 
  ###
  ### menu
  unless file_loaded?(__FILE__)
    menu=UI.menu("Plugins").add_submenu("Copy Materials...")
    menu.add_item("To Nearest Below"){self.copymaterials()}
  end
  file_loaded(__FILE__)
	
end

chanz · 10 Sept 2018, 19:38

Thanks again for the reply TIG. Unfortunately, I see the same issues. To verify it wasn't the small differences in faces from DropVertices, I made a copy of the bottom textured model and moved it directly above. I removed the top materials and then ran the script. UV issue is still there. Have you actually downloaded the file and run this script with the top mesh faces selected? Have you seen the UV issues or did it look okay for you? Honestly, I guess I will just give up at this point.

I have figured out another sort of workaround where I make a sandbox mesh above the original, run this script we wrote (which does perfectly with the texture and UVs when the raycast is from a flat surface), then use UVToolkit to save the UVs, then drop the vertices and then restore the UVs. It works. A few extra steps but this script has been enough of a headache.

Regardless, thanks for your help.