lerp debugging

gamebridge/src/main.rs

@@ -20,6 +20,7 @@ pub(crate) struct State {
     controller: [u8; 4],
     last_got: Box<Instant>,
     ok: bool,
+    frame: u64,
 }
 
 pub(crate) type MTState = Arc<RwLock<State>>;
@@ -36,6 +37,7 @@ fn main() -> Result<()> {
             controller: [0; 4],
             last_got: Box::new(Instant::now()),
             ok: true,
+            frame: 0,
         };
 
         Arc::new(RwLock::new(st))
@@ -48,6 +50,10 @@ fn main() -> Result<()> {
         spawn(move || twitch::run(st));
     }
 
+    const LERP_TIME: f64 = 1.0; // 15 frames to lerp stick positions down to 0
+    let mut xmax_frame: u64 = 0;
+    let mut ymax_frame: u64 = 0;
+
     loop {
         let mut data = [0; 3];
         debug!("waiting for vblank");
@@ -58,9 +64,56 @@ fn main() -> Result<()> {
         match str {
             "OK\n" => {
                 let mut data = st.write().unwrap();
+                data.frame += 1;
+
+                let mut stickx = data.controller[2] as i8;
+                let mut sticky = data.controller[3] as i8;
+
+                let dist = stick_distance(stickx, sticky);
+                if dist <= 10 {
+                    stickx = 0;
+                    sticky = 0;
+                    xmax_frame = 0;
+                    ymax_frame = 0;
+                }
+
+                stickx = match stickx {
+                    0 => stickx,
+                    127 => {
+                        xmax_frame = data.frame;
+                        stickx - 10
+                    },
+                    -128 => {
+                        xmax_frame = data.frame;
+                        stickx + 10
+                    },
+                    _ => {
+                        let t = (data.frame - xmax_frame) as f64 / (LERP_TIME as f64);
+                        lerp(stickx, 0, t)
+                    },
+                };
+
+                sticky = match stickx {
+                    0 => sticky,
+                    127 => {
+                        ymax_frame = data.frame;
+                        sticky - 10
+                    },
+                    -128 => {
+                        ymax_frame = data.frame;
+                        sticky + 10
+                    },
+                    _ => {
+                        let t = (data.frame - ymax_frame) as f64 / (LERP_TIME as f64);
+                        lerp(sticky, 0, t)
+                    },
+                };
+
                 input.write(&data.controller)?;
                 data.controller[0] = 0;
                 data.controller[1] = 0;
+                data.controller[2] = stickx as u8;
+                data.controller[3] = sticky as u8;
             }
             "BYE" => {
                 warn!("asked to exit by the game");
@@ -73,3 +126,42 @@ fn main() -> Result<()> {
         };
     }
 }
+
+fn lerp(start: i8, end: i8, t: f64) -> i8 {
+    (start as f64 * (1.0 - t) + (end as f64) * t) as i8
+}
+
+fn stick_distance(x: i8, y: i8) -> i8 {
+    let x = (x as f64).powi(2);
+    let y = (y as f64).powi(2);
+    (x + y).sqrt() as i8
+}
+
+#[cfg(test)]
+mod test {
+    #[test]
+    fn lerp_scale() {
+        for case in [(0.1, 10), (0.5, 31)].iter() {
+            let t = case.0;
+            let start = 127.0 * t;
+            assert_eq!(crate::lerp(start as i8, 0, t), case.1);
+        }
+    }
+
+    #[test]
+    fn stick_distance() {
+        for case in [
+            (0, 0, 0),
+            (127, 0, 127),
+            (64, 64, 90),
+            (-64, 64, 90),
+            (-64, -64, 90),
+        ]
+        .iter()
+        {
+            let x = case.0;
+            let y = case.1;
+            assert_eq!(crate::stick_distance(x, y), case.2);
+        }
+    }
+}

gamebridge/src/twitch.rs

@@ -70,8 +70,6 @@ async fn run_loop(
     }
 
     wait_and_join(&mut control, &mut dispatcher, channels).await;
-    let mut stickx: i8 = 0;
-    let mut sticky: i8 = 0;
 
     loop {
         tokio::select! {
@@ -84,6 +82,14 @@ async fn run_loop(
             Some(msg) = pmsg.next() => {
                 let mut hi = HiButtons::NONE;
                 let mut lo = LoButtons::NONE;
+                let mut stickx: i8 = 0;
+                let mut sticky: i8 = 0;
+
+                {
+                    let data = st.read().unwrap();
+                    stickx = data.controller[2] as i8;
+                    sticky = data.controller[3] as i8;
+                }
 
                 let mut data = msg.data.to_string();
                 let data = data.to_ascii_lowercase();