     triangle-a triangle-b v- :> triangle-hi
 
     diagonal scale-matrix4 :> diagonal-m
-    triangle-hi { 3 0 1 3 } vshuffle :> tri1
-    triangle-hi { 3 3 2 3 } vshuffle
-    triangle-lo { 0 3 3 3 } vshuffle v+ :> tri2
-    triangle-lo { 1 2 3 3 } vshuffle :> tri3
-    tri1 triangle-m rows>> set-first
-    tri2 triangle-m rows>> set-second
-    tri3 triangle-m rows>> set-third
-    float-4 new triangle-m rows>> set-fourth
+
+    triangle-hi { 3 0 1 3 } vshuffle
+    triangle-hi { 3 3 2 3 } vshuffle triangle-lo { 0 3 3 3 } vshuffle v+
+    triangle-lo { 1 2 3 3 } vshuffle
+    float-4 new
+
+    triangle-m set-rows drop
 
     diagonal-m triangle-m m4+ ;
 
 TYPED:: frustum-matrix4 ( xy: float-4 near: float far: float -- matrix: matrix4 )
     matrix4 (struct) :> c
 
-    float-4{ 0.0 0.0 -1.0 0.0 } :> c4
-
     near near near far + 2 near far * * float-4-boa :> num
     { t t f f } xy near far - float-4-with v? :> denom
     num denom v/ :> fov
 
-    fov { 0 0 0 0 } vshuffle { t f f f } vmask :> c1
-    fov { 1 1 1 1 } vshuffle { f t f f } vmask :> c2
-    fov { 2 2 2 3 } vshuffle { f f t t } vmask :> c3
+    fov { 0 0 0 0 } vshuffle { t f f f } vmask
+    fov { 1 1 1 1 } vshuffle { f t f f } vmask
+    fov { 2 2 2 3 } vshuffle { f f t t } vmask
+    float-4{ 0.0 0.0 -1.0 0.0 }
 
-    c1 c rows>> set-first
-    c2 c rows>> set-second
-    c3 c rows>> set-third
-    c4 c rows>> set-fourth
+    c set-rows ;
 
-    c ;
-

TYPED:: m4. ( a: matrix4 b: matrix4 -- c: matrix4 )
    matrix4 (struct) :> c

    a rows>> first  :> a1
    a rows>> second :> a2
    a rows>> third  :> a3
    a rows>> fourth :> a4
    b rows>> first  :> b1
    b rows>> second :> b2
    b rows>> third  :> b3
    b rows>> fourth :> b4

    a1 { 0 0 0 0 } vshuffle b1 v* :> c1a
    a2 { 0 0 0 0 } vshuffle b1 v* :> c2a
    a3 { 0 0 0 0 } vshuffle b1 v* :> c3a
    a4 { 0 0 0 0 } vshuffle b1 v* :> c4a

    a1 { 1 1 1 1 } vshuffle b2 v* c1a v+ :> c1b 
    a2 { 1 1 1 1 } vshuffle b2 v* c2a v+ :> c2b
    a3 { 1 1 1 1 } vshuffle b2 v* c3a v+ :> c3b
    a4 { 1 1 1 1 } vshuffle b2 v* c4a v+ :> c4b

    a1 { 2 2 2 2 } vshuffle b3 v* c1b v+ :> c1c 
    a2 { 2 2 2 2 } vshuffle b3 v* c2b v+ :> c2c
    a3 { 2 2 2 2 } vshuffle b3 v* c3b v+ :> c3c
    a4 { 2 2 2 2 } vshuffle b3 v* c4b v+ :> c4c

    a1 { 3 3 3 3 } vshuffle b4 v* c1c v+ :> c1 
    a2 { 3 3 3 3 } vshuffle b4 v* c2c v+ :> c2
    a3 { 3 3 3 3 } vshuffle b4 v* c3c v+ :> c3
    a4 { 3 3 3 3 } vshuffle b4 v* c4c v+ :> c4

    c1 c rows>> set-first
    c2 c rows>> set-second
    c3 c rows>> set-third
    c4 c rows>> set-fourth

    c ;

CONSTANT: identity-matrix4
    S{ matrix4 f


    float-4{ 0.0 0.0 0.0 1.0 } :> c4
    { t t t f } offset c4 v? :> offset'

    offset' { 3 3 3 0 } vshuffle { t f f t } vmask
    offset' { 3 3 3 1 } vshuffle { f t f t } vmask
    offset' { 3 3 3 2 } vshuffle { f f t t } vmask
    c4

    c set-rows ;

TYPED:: rotation-matrix4 ( axis: float-4 theta: float -- matrix: matrix4 )
    !   x*x + c*(1.0 - x*x)   x*y*(1.0 - c) - s*z   x*z*(1.0 - c) + s*y   0
