Add camera matrix accessors

Author: jdahlstrom

core/src/render/cam.rs

@@ -206,9 +206,18 @@ impl<T> Camera<T> {
 }
 
 impl<T: Transform> Camera<T> {
+    /// Returns the camera matrix.
+    pub fn world_to_view(&self) -> Mat4<World, View> {
+        self.transform.world_to_view()
+    }
+    /// Returns the inverse camera matrix.
+    pub fn view_to_world(&self) -> Mat4<View, World> {
+        self.world_to_view().inverse()
+    }
+
     /// Returns the composed camera and projection matrix.
     pub fn world_to_project(&self) -> ProjMat3<World> {
-        self.transform.world_to_view().then(&self.project)
+        self.world_to_view().then(&self.project)
     }
 
     /// Renders the given geometry from the viewpoint of this camera.

demos/src/bin/sprites.rs

@@ -64,7 +64,7 @@ fn main() {
         let modelview = rotate_x(theta * 0.2)
             .then(&rotate_z(theta * 0.14))
             .to()
-            .then(&cam.transform.world_to_view());
+            .then(&cam.world_to_view());
 
         render(
             &tris,