Snippet for getting UVQ and UV data from 3D points

Example Usage

model = Sketchup.active_model
face = model.selection[0]

uvqh = UVQHelper.new(face)

face.vertices.size.times { |i| p uvqh.transform3DtoUVQ(true, face.vertices[i].position) }
# => Point3d(0, 0, 1)
# => Point3d(1, 0, 1)
# => Point3d(0.839757, 0.451277, 0.451277)
# => Point3d(-0.160243, 0.451277, 0.451277)

face.vertices.size.times { |i| p uvqh.transform3DtoUV(true, face.vertices[i].position) }
# => Point3d(0, 0, 1)
# => Point3d(1, 0, 1)
# => Point3d(1.86084, 1, 1)
# => Point3d(-0.355088, 1, 1)

UVQHelper

class UVQHelper

  # @param [Sketchup::Face] face
  # @param [Boolean] front
  # @param [Boolean] back
  # @param [Sketchup::TextureWriter] texturewriter
  def initialize(face, front = true, back = true,
                 texturewriter = nil)
    args = [front, back]
    args << texturewriter if texturewriter
    @uvh = face.get_UVHelper(*args)
  end

  # Simple wrapper over UVHelper.get_front_UVQ. 3D points are projected to
  # the plane of the face and then a UVQ value is returned.
  #
  # @param [Boolean] front
  # @param [Geom::Point3d] point
  #
  # @return [Geom::Point3d] UVQ point
  def transform3DtoUVQ(front, point)
    if front
      @uvh.get_front_UVQ(point)
    else
      @uvh.get_back_UVQ(point)
    end
  end

  # 3D points are projected to the plane of the face and then a UV value is
  # returned.
  #
  # @param [Boolean] front
  # @param [Geom::Point3d] point
  #
  # @return [Geom::Point3d] UV point
  def transform3DtoUV(front, point)
    uvq = nil
    if front
      uvq = @uvh.get_front_UVQ(point)
    else
      uvq = @uvh.get_back_UVQ(point)
    end
    Geom::Point3d.new(uvq.x / uvq.z, uvq.y / uvq.z, 1.0)
  end

end # class