First working z-buffer.

@@ -156,6 +156,10 @@ where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
     fn edge(self, b :&Self) -> Vec<Self> {
         self.edge_iter(b).collect()
     }
+
+    fn face(edges :&[Self]) -> Vec<Self> {
+        edges.to_vec()
+    }
 }
 
 impl<T> Display for Coordinate<T> {

@@ -155,9 +155,10 @@ where T: Add + Sub + Neg + Mul + Div + Debug + Copy + Trig + From<i32> {
 
 pub struct Camera<T>
 where T: Add + Sub + Neg + Mul + Div + Debug + Copy + Trig + From<i32> {
-    width   :T,
-    height  :T,
-    project :TMatrix<T>,
+    width    :T,
+    height   :T,
+    distance :T,
+    project  :TMatrix<T>,
 }
 
 pub struct DirectLight<T>
@@ -181,15 +182,20 @@ where T: Add<Output = T> + Sub<Output = T> + Neg<Output = T>
         let     wh    = width / 2.into();
         let     hh    = height / 2.into();
 
-        Camera { width:   width
-               , height:  height
-               , project: TMatrix::new(
+        Camera { width:    width
+               , height:   height
+               , distance: d
+               , project:  TMatrix::new(
                      (     fov, 0.into(),       wh, 0.into())
                    , (0.into(),      fov,       hh, 0.into())
                    , (0.into(), 0.into(),        d, 1.into())
                    , (0.into(), 0.into(), 1.into(), 0.into()) ) }
     }
 
+    pub fn get_distance(&self) -> T {
+        self.distance
+    }
+
     pub fn get_projection(&self) -> TMatrix<T> {
         self.project
     }
@@ -253,11 +259,6 @@ where T: Add<Output = T> + Sub<Output = T> + Neg<Output = T>
         let zc :T = T::sqrt(f3).unwrap() / f3 * a;
         let ah :T = a / 2.into();
 
-        // half the height in y
-        let _yh :T = a /  f6 * T::sqrt(f6).unwrap();
-        // half the deeps in z
-        let _zh :T = T::sqrt(f3).unwrap() / f4 * a;
-
         let ps = vec!( Point::new( f0,  yc,  f0)
                      , Point::new(-ah, -yi, -zi)
                      , Point::new( ah, -yi, -zi)
@@ -285,8 +286,6 @@ where T: Add<Output = T> + Sub<Output = T> + Neg<Output = T>
 
         let fs = vec!(Face::new(vec!(0, 1, 2), &ps));
 
-        println!("== {:?}", fs);
-
         Polyeder{ points: ps, faces: fs }
     }
 
@@ -347,7 +346,6 @@ where T: Add<Output = T> + Sub<Output = T> + Neg<Output = T>
         // matrix we do not need to do it here.
         let to_coord = |p :&usize| {
             let Point(v, _) = camera.project(self.points[*p]);
-            // println!("== {:?} / {:?}", self.points[*p], (v.z() - 1.into()).recip());
             Coordinate(T::round(&v.x()), T::round(&v.y()), v.z() - 1.into())
         };
         let to_poly  = |f :&Face<T>| {
@@ -378,7 +376,7 @@ where T: Add<Output = T> + Sub<Output = T> + Neg<Output = T>
                        }};
 
         let mut ps :Vec<(Polygon<T>, u32)> = self.faces.iter()
-                                       . filter_map(to_poly).collect();
+                                           . filter_map(to_poly).collect();
         // this sorts by the color value which is no longer neccessary as soon
         // as the z-buffer is complete.
         ps.sort_by(|a, b| a.1.cmp(&b.1));

@@ -35,8 +35,7 @@ use fractional::fractional::{Fractional, from_vector};
 use fractional::trigonometry::Trig;
 use fractional::vector::Vector;
 use fractional::transform::{TMatrix, Transformable};
-
-use fractional::xcb::{XcbEasel, XcbCanvas};
+use fractional::xcb::XcbEasel;
 
 use fractional::geometry::{Camera,DirectLight,Polyeder,Primitives};
 
@@ -322,8 +321,8 @@ fn _democanvas<T>( xcb         :&XcbEasel
                                                     // was 50.
 
     canvas.set_title(title);
-    <XcbCanvas as Canvas<T>>::init_events(&canvas);
-    <XcbCanvas as Canvas<T>>::start_events(&canvas, tx.clone());
+    canvas.init_events();
+    canvas.start_events(tx.clone());
 
     thread::spawn(move || {
         let     start = Instant::now();
@@ -348,7 +347,7 @@ fn _democanvas<T>( xcb         :&XcbEasel
             //let objects = vec!( (tetrahedron.transform(&rot1), 0xFFFF00) );
             //let objects = vec!( (triangle.transform(&rot1), 0xFFFF00) );
 
-            <XcbCanvas as Canvas<T>>::clear(&mut canvas);
+            canvas.clear();
 
             for (o, color) in objects {
                 for (pg, c) in o.project(&camera, &light, color) {
@@ -367,11 +366,10 @@ fn _democanvas<T>( xcb         :&XcbEasel
             }
 
             last = last + step*(f + 1);
-            <XcbCanvas as Canvas<T>>::put_text( &canvas
-                                              , Coordinate(10, 15, 0.into())
-                                              , &format!( "sleep: {:?}"
-                                              , last - Instant::now() ));
-            <XcbCanvas as Canvas<T>>::show(&canvas);
+            canvas.put_text( Coordinate(10, 15, 0.into())
+                           , &format!( "sleep: {:?}"
+                           , last - Instant::now() ));
+            canvas.show();
             thread::sleep(last - Instant::now());
         }
     });

@@ -24,19 +24,21 @@ use std::sync::Arc;
 use std::ptr; //::{null, null_mut};
 use std::thread;
 use std::sync::mpsc;
+use std::ops::{Add, Sub, Div};
 
 use crate::easel::{Easel, Canvas, Drawable, Coordinate, Coordinates};
 
 #[derive(Clone)]
 pub struct XcbEasel (Arc<xcb::Connection>, i32);
 
-pub struct XcbCanvas<'a> { conn   :Arc<xcb::Connection>
-                         , width  :u16
-                         , height :u16
-                         , window :u32
-                         , pixmap :u32
-                         , gc     :u32
-                         , shm    :Box<&'a mut [u32]> }
+pub struct XcbCanvas<'a, T> { conn   :Arc<xcb::Connection>
+                            , width  :u16
+                            , height :u16
+                            , window :u32
+                            , pixmap :u32
+                            , gc     :u32
+                            , zbuf   :Vec<T>
+                            , shm    :Box<&'a mut [u32]> }
 
 impl XcbEasel {
     pub fn new() -> Result<XcbEasel, xcb::ConnError> {
@@ -55,7 +57,10 @@ impl XcbEasel {
         self.setup().roots().nth(*num as usize)
     }
 
-    pub fn canvas<'a>(&self, width :u16, height :u16) -> Option<XcbCanvas<'a>> {
+    pub fn canvas<'a, T>( &self
+                        , width  :u16
+                        , height :u16) -> Option<XcbCanvas<'a, T>>
+    where T: Clone + From<i32> {
         let Self(conn, _) = self;
         let conn          = conn.clone();
         let screen        = match self.screen() {
@@ -80,6 +85,7 @@ impl XcbEasel {
                       , &[ (xcb::GC_FOREGROUND, screen.white_pixel())
                       , (xcb::GC_GRAPHICS_EXPOSURES, 0) ] );
 
+        let zbuf :Vec<T> = vec!(0.into(); (width * height) as usize);
         let (shmid, shm) = getshm((width * height) as usize);
         xcb::shm::attach(&conn, shmseg, shmid as u32, false);
         unsafe { libc::shmctl(shmid, libc::IPC_RMID, ptr::null_mut()); }
@@ -96,11 +102,12 @@ impl XcbEasel {
                       , window: window
                       , pixmap: pixmap
                       , gc:     gc
+                      , zbuf:   zbuf
                       , shm:    Box::new(shm) } )
     }
 }
 
-impl<'a> XcbCanvas<'a> {
+impl<'a, T> XcbCanvas<'a, T> {
     pub fn set_title(&self, title :&str) {
         let c = xcb::change_property_checked( &self.conn
                                             , xcb::PROP_MODE_REPLACE as u8
@@ -129,7 +136,9 @@ fn getshm<'a>(size :usize) -> (i32, &'a mut [u32]) {
 
 impl Easel for XcbEasel {}
 
-impl<'a,T> Canvas<T> for XcbCanvas<'a> {
+impl<'a, T> Canvas<T> for XcbCanvas<'a, T>
+where T: Add<Output = T> + Sub<Output = T> + Div<Output = T>
+       + Copy + From<i32> + PartialOrd {
     fn init_events(&self) {
         let mask = [( xcb::CW_EVENT_MASK, xcb::EVENT_MASK_EXPOSURE
                                         | xcb::EVENT_MASK_KEY_PRESS
@@ -216,6 +225,7 @@ impl<'a,T> Canvas<T> for XcbCanvas<'a> {
     }
 
     fn clear(&mut self) {
+        self.zbuf = vec!(0.into(); self.zbuf.len());
         unsafe {
             let ptr = self.shm.as_mut_ptr();
             ptr::write_bytes( ptr, 0
@@ -227,9 +237,12 @@ impl<'a,T> Canvas<T> for XcbCanvas<'a> {
         let Coordinates(c)            = d.plot();
         let Coordinate(xofs, yofs, _) = ofs;
 
-        for Coordinate(x, y, _) in c {
+        for Coordinate(x, y, zr) in c {
             let idx :usize = ((y+yofs)*(self.width as i32)+x+xofs) as usize;
-            self.shm[idx] = color;
+            if self.zbuf[idx] < zr {
+                self.zbuf[idx] = zr;
+                self.shm[idx] = color;
+            }
         }
     }
 
@@ -241,11 +254,13 @@ impl<'a,T> Canvas<T> for XcbCanvas<'a> {
     }
 
     fn set_pixel(&mut self, c :Coordinate<T>, color :u32) {
-        let Coordinate(x, y, _) = c;
+        let Coordinate(x, y, zr) = c;
         let idx :usize = (y * (self.width as i32) + x) as usize;
 
-        //print!("({}, {})", idx, color);
-        self.shm[idx] = color;
+        if self.zbuf[idx] < zr {
+            self.zbuf[idx] = zr;
+            self.shm[idx] = color;
+        }
     }
 
     fn show(&self) {