I want to join Archimedian mesh2 objects precisely to one another (think 
  Magnetix).  Is there a way to fish normal and vertex data out of a 
declared mesh2 given a face index or will I have to create a separate 
vertex array?

Is there a variant of ReorientCenter that takes 6 points, 3 from one 
triangle and three from the other, that will line up the first triangle 
to exactly fit the other?

#macro ReorientTriangle(p1,p2,p3,p4,p5,p6)
   #local tr1 = transform { matrix <p1.x,p1.y,p1.z, p2.x,p2.y,p2.z, 
p3.x,p3.y,p3.z, 0,0,0> inverse }
   #local tr2 = transform { matrix <p4.x,p4.y,p4.z, p5.x,p5.y,p5.z, 
p6.x,p6.y,p6.z, 0,0,0> }
   transform tr1
   transform tr2
#end

// Tetrahedron (Tetrad)
#declare aTetrad = sqrt(2);

#declare Tetrad = mesh2 {
	vertex_vectors { 4,
		<-.5, -.5, -.5>,
		<0.5, -.5, 0.5>,
		<-.5, 0.5, 0.5>,
		<0.5, 0.5, -.5>
	}
	face_indices { 4,
		<0,1,2>,<0,2,3>,<0,3,1>,<3,2,1>
	}
	//Reorient(<-1,-1,-1>,y)
}

#declare vTetrad = array[4] {
	<-.5, -.5, -.5>,
	<0.5, -.5, 0.5>,
	<-.5, 0.5, 0.5>,
	<0.5, 0.5, -.5>
}

// Cuboctahedron (Cuboct)
#declare aCuboct = sqrt(0.5);

#declare Cuboct = mesh2 {
	vertex_vectors { 18,
		<0,-0.5,-0.5>,
		<0, 0.5,-0.5>,
		<0,-0.5, 0.5>,
		<0, 0.5, 0.5>,
		<-0.5, 0,-0.5>,
		< 0.5, 0,-0.5>,
		<-0.5, 0, 0.5>,
		< 0.5, 0, 0.5>,
		<-0.5,-0.5, 0>,
		< 0.5,-0.5, 0>,
		<-0.5, 0.5, 0>,
		< 0.5, 0.5, 0>,
		<-0.5, 0.0, 0.0>,
		< 0.5, 0.0, 0.0>,
		< 0.0,-0.5, 0.0>,
		< 0.0, 0.5, 0.0>,
		< 0.0, 0.0,-0.5>,
		< 0.0, 0.0, 0.5>
	}
	face_indices { 32,
		<8,4,0>,<1,4,10>,<11,5,1>,<0,5,9>,
		<2,6,8>,<9,7,2>,<3,7,11>,<10,6,3>,
		<4,8,12>,<8,6,12>,<6,10,12>,<10,4,12>,
		<9,5,13>,<7,9,13>,<11,7,13>,<5,11,13>,
		<0,8,14>,<8,2,14>,<2,9,14>,<9,0,14>,
		<10,1,15>,<3,10,15>,<11,3,15>,<1,11,15>,
		<0,4,16>,<4,1,16>,<1,5,16>,<5,0,16>,
		<6,2,17>,<3,6,17>,<7,3,17>,<2,7,17>,
	}
}

#declare vCuboct = array[18] {
	<0,-0.5,-0.5>,
	<0, 0.5,-0.5>,
	<0,-0.5, 0.5>,
	<0, 0.5, 0.5>,
	<-0.5, 0,-0.5>,
	< 0.5, 0,-0.5>,
	<-0.5, 0, 0.5>,
	< 0.5, 0, 0.5>,
	<-0.5,-0.5, 0>,
	< 0.5,-0.5, 0>,
	<-0.5, 0.5, 0>,
	< 0.5, 0.5, 0>,
	<-0.5, 0.0, 0.0>,
	< 0.5, 0.0, 0.0>,
	< 0.0,-0.5, 0.0>,
	< 0.0, 0.5, 0.0>,
	< 0.0, 0.0,-0.5>,
	< 0.0, 0.0, 0.5>
}

#declare _aspect = image_width/image_height;

light_source { x*50, rgb <1,0,0> }
light_source { y*50, rgb <0,1,0> }
light_source { z*50, rgb <0,0,1> }

camera {
   location <-2.0, 2.0, 0.0>
   look_at <0.0, 0.0,  0.0>
   rotate  y*20
}

object { Cuboct scale 1 pigment { rgb 1 } }
object { Tetrad
   ReorientTriangle( 
vTetrad[0],vTetrad[2],vTetrad[1],vCuboct[1],vCuboct[4],vCuboct[10] )
   pigment { rgb 0.75 }
}

I tested this and got an unexpected result... the fourth point in the 
tetrahedron is way off course while the first three points are spot on. 
  I need a set of translations and rotations that have the normals 
facing each other, the face centers and first points matching.

Ideas are welcome.

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