first step done: we have a custom and updatable matrix

src/main.rs

@@ -1,8 +1,10 @@
 use crate::scene::*;
-use bevy::{prelude::*, window::PresentMode};
+use bevy::{prelude::*, window::PresentMode, render::camera::CameraProjectionPlugin};
+use offaxis::{offaxis_camera_setup, OffAxisProjection};
 
 mod offaxis;
 mod scene;
+mod screeninfo;
 
 fn main() {
     App::new()
@@ -35,7 +37,14 @@ fn main() {
         // )
         // .add_system(hello_world)
         .add_startup_system(build_scene)
-        .add_system(print_positions)
+        .add_system(modify_projection)
+        .add_startup_system(offaxis_camera_setup)
+        // .add_system(print_positions)
+        // .add_system(modify_frustum)
+
+        .add_plugin(CameraProjectionPlugin::<OffAxisProjection>::default())
+
+        .add_system(update_offaxis)
         .run();
 }
 
@@ -50,3 +59,14 @@ fn cycle_msaa(input: Res<Input<KeyCode>>, mut msaa: ResMut<Msaa>) {
         }
     }
 }
+
+fn update_offaxis(mut query : Query<&mut OffAxisProjection>)
+{
+    for mut q in query.iter_mut() {
+
+        // we fake access to far for updating the matrix
+        (*q).far *= 1.0;
+
+        println!("Update {:?}",q);
+    }
+}