fix typo and import PI

[c0deaddict]

Hello,

Thanks for your amazing work on this book. I've just completed the last available chapter of the book, and it was a very fun experience.

I encountered two small typos and one missing import, which are fixed in this PR.

Another thing that I encountered was that DeviceEvent::MouseWheel and DeviceEvent::Button would not trigger on my PC, instead i've used WindowEvent::MouseWheel and WindowEvent::MouseInput that did trigger. My guess it has something to do with the environment i'm running the program in (sway on NixOS unstable). For reference here is my event loop run:

    event_loop.run(|event, control_handle| {
        control_handle.set_control_flow(ControlFlow::Poll);
        match event {
            Event::WindowEvent { event, .. } => match event {
                WindowEvent::CloseRequested => control_handle.exit(),
                WindowEvent::RedrawRequested => {
                    // Wait for the next available frame buffer.
                    let frame: wgpu::SurfaceTexture = surface
                        .get_current_texture()
                        .expect("failed to get current texture");

                    let render_target = frame
                        .texture
                        .create_view(&wgpu::TextureViewDescriptor::default());

                    renderer.render_frame(&camera, &render_target);

                    frame.present();
                    window.request_redraw();
                },
                WindowEvent::MouseWheel { delta, .. } =>  {
                    let delta = match delta {
                        MouseScrollDelta::PixelDelta(delta) => 0.001 * delta.y as f32,
                        MouseScrollDelta::LineDelta(_, y) => y * 0.05,
                    };
                    camera.zoom(delta);
                    renderer.reset_samples();
                },
                WindowEvent::MouseInput { button, state, .. } => {
                    let pressed = state == ElementState::Pressed;
                    match button {
                        winit::event::MouseButton::Left => left_mouse_button_pressed = pressed,
                        winit::event::MouseButton::Right => right_mouse_button_pressed = pressed,
                        _ => (),
                    }
                }
                _ => (),
            },
            Event::DeviceEvent { event, .. } =>  match event {
                DeviceEvent::MouseMotion { delta: (dx, dy) } => {
                    let dx = dx as f32 *  0.01;
                    let dy = dy as f32 * -0.01;
                    if left_mouse_button_pressed {
                        camera.orbit(dx, dy);
                        renderer.reset_samples();
                    }
                    if right_mouse_button_pressed {
                        camera.pan(dx, dy);
                        renderer.reset_samples();
                    }
                },
                _ => (),
            },
            _ => (),
        }
    })?;

[armansito]

Thank you for the kind words and corrections!

[armansito]

Another thing that I encountered was that DeviceEvent::MouseWheel and DeviceEvent::Button would not trigger on my PC, instead i've used WindowEvent::MouseWheel and WindowEvent::MouseInput that did trigger. My guess it has something to do with the environment i'm running the program in (sway on NixOS unstable). For reference here is my event loop run:

    event_loop.run(|event, control_handle| {
        control_handle.set_control_flow(ControlFlow::Poll);
        match event {
            Event::WindowEvent { event, .. } => match event {
                WindowEvent::CloseRequested => control_handle.exit(),
                WindowEvent::RedrawRequested => {
                    // Wait for the next available frame buffer.
                    let frame: wgpu::SurfaceTexture = surface
                        .get_current_texture()
                        .expect("failed to get current texture");

                    let render_target = frame
                        .texture
                        .create_view(&wgpu::TextureViewDescriptor::default());

                    renderer.render_frame(&camera, &render_target);

                    frame.present();
                    window.request_redraw();
                },
                WindowEvent::MouseWheel { delta, .. } =>  {
                    let delta = match delta {
                        MouseScrollDelta::PixelDelta(delta) => 0.001 * delta.y as f32,
                        MouseScrollDelta::LineDelta(_, y) => y * 0.05,
                    };
                    camera.zoom(delta);
                    renderer.reset_samples();
                },
                WindowEvent::MouseInput { button, state, .. } => {
                    let pressed = state == ElementState::Pressed;
                    match button {
                        winit::event::MouseButton::Left => left_mouse_button_pressed = pressed,
                        winit::event::MouseButton::Right => right_mouse_button_pressed = pressed,
                        _ => (),
                    }
                }
                _ => (),
            },
            Event::DeviceEvent { event, .. } =>  match event {
                DeviceEvent::MouseMotion { delta: (dx, dy) } => {
                    let dx = dx as f32 *  0.01;
                    let dy = dy as f32 * -0.01;
                    if left_mouse_button_pressed {
                        camera.orbit(dx, dy);
                        renderer.reset_samples();
                    }
                    if right_mouse_button_pressed {
                        camera.pan(dx, dy);
                        renderer.reset_samples();
                    }
                },
                _ => (),
            },
            _ => (),
        }
    })?;

Thank you for the report. I ran into a different issue related to mouse handling that also got resolved with the WindowEvent equivalent, so I think it makes sense to change the code (I filed #23 to track that). PRs are always welcome :)