diff --git a/demo/common/src/lib.rs b/demo/common/src/lib.rs
index fd1d3856..2121a93d 100644
--- a/demo/common/src/lib.rs
+++ b/demo/common/src/lib.rs
@@ -25,6 +25,7 @@ use clap::{App, Arg};
 use pathfinder_geometry::basic::vector::{Vector2F, Vector2I};
 use pathfinder_geometry::basic::rect::RectF;
 use pathfinder_geometry::basic::transform2d::Transform2DF;
+use pathfinder_geometry::basic::transform3d::Transform3DF;
 use pathfinder_geometry::color::ColorU;
 use pathfinder_gl::GLDevice;
 use pathfinder_gpu::Device;
@@ -53,6 +54,9 @@ const CAMERA_SCALE_SPEED_2D: f32 = 6.0;
 // How much the scene is scaled when a zoom button is clicked.
 const CAMERA_ZOOM_AMOUNT_2D: f32 = 0.1;
 
+// Half of the eye separation distance.
+const DEFAULT_EYE_OFFSET: f32 = 0.025;
+
 const LIGHT_BG_COLOR: ColorU = ColorU {
     r: 248,
     g: 248,
@@ -328,9 +332,18 @@ impl<W> DemoApp<W> where W: Window {
                         ..
                     } = self.camera
                     {
-		        // TODO: really we should lerp all the eye transforms to get the new scene transform
-                        *scene_transform = new_eye_transforms[0];
                         *eye_transforms = new_eye_transforms;
+                        // Calculate the new scene transform by lerp'ing the eye transforms.
+                        *scene_transform = eye_transforms[0];
+                        for (index, eye_transform) in eye_transforms.iter().enumerate().skip(1) {
+                            let weight = 1.0 / (index + 1) as f32;
+                            scene_transform.perspective.transform = scene_transform.perspective.transform.lerp(weight, &eye_transform.perspective.transform);
+                            scene_transform.modelview_to_eye = scene_transform.modelview_to_eye.lerp(weight, &eye_transform.modelview_to_eye);
+                         }
+                        // TODO: calculate the eye offset from the eye transforms?
+                        let z_offset = -DEFAULT_EYE_OFFSET * scene_transform.perspective.transform.c0.x();
+                        scene_transform.modelview_to_eye = scene_transform.modelview_to_eye
+                            .pre_mul(&Transform3DF::from_translation(0.0, 0.0, z_offset));
                     }
                 }
                 Event::KeyDown(Keycode::Alphanumeric(b'w')) => {
diff --git a/geometry/src/basic/transform3d.rs b/geometry/src/basic/transform3d.rs
index 9b7aa4bd..bdd71c0c 100644
--- a/geometry/src/basic/transform3d.rs
+++ b/geometry/src/basic/transform3d.rs
@@ -176,6 +176,15 @@ impl Transform3DF {
         )
     }
 
+    /// Linearly interpolate between transforms
+    pub fn lerp(&self, weight: f32, other: &Transform3DF) -> Transform3DF {
+        let c0 = self.c0 * F32x4::splat(weight) + other.c0 * F32x4::splat(1.0 - weight);
+        let c1 = self.c1 * F32x4::splat(weight) + other.c1 * F32x4::splat(1.0 - weight);
+        let c2 = self.c2 * F32x4::splat(weight) + other.c2 * F32x4::splat(1.0 - weight);
+        let c3 = self.c3 * F32x4::splat(weight) + other.c3 * F32x4::splat(1.0 - weight);
+        Transform3DF { c0, c1, c2, c3 }
+    }
+
     /// Just like `gluPerspective()`.
     #[inline]
     pub fn from_perspective(fov_y: f32, aspect: f32, z_near: f32, z_far: f32) -> Transform3DF {