From 5f3adf0925797bbf3b8e2f2a290fb70f94295b21 Mon Sep 17 00:00:00 2001
From: Christoph Urlacher <christoph.urlacher@protonmail.com>
Date: Tue, 24 Feb 2026 17:24:35 +0100
Subject: [PATCH] wip: don't wait for physics data in render thread

---
 src/main.cpp    | 27 ++++++++++++++-------------
 src/physics.cpp |  5 ++++-
 src/state.cpp   |  4 ++--
 3 files changed, 20 insertions(+), 16 deletions(-)

diff --git a/src/main.cpp b/src/main.cpp
index 66f54c6..90173ae 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -55,23 +55,24 @@ auto main(int argc, char *argv[]) -> int {
     state.UpdateGraph(); // Add state added after user input
 
     // Read positions from physics thread
+    FrameMarkStart("MainThreadConsumeLock");
     {
       std::unique_lock<LockableBase(std::mutex)> lock(physics.state.data_mtx);
-      physics.state.data_ready_cnd.wait(lock, [&] {
-        return physics.state.data_ready || !physics.state.running.load();
-      });
-      if (!physics.state.running.load()) {
-        // Running turned false while we were waiting for the condition
-        break;
+
+      // Only copy data if any has been produced
+      if (physics.state.data_ready) {
+        masses = physics.state.masses;
+        springs = physics.state.springs;
+
+        physics.state.data_ready = false;
+        physics.state.data_consumed = true;
+
+        lock.unlock();
+        // Notify the physics thread that data has been consumed
+        physics.state.data_consumed_cnd.notify_all();
       }
-
-      masses = physics.state.masses;
-      springs = physics.state.springs;
-
-      physics.state.data_ready = false;
-      physics.state.data_consumed = true;
     }
-    physics.state.data_consumed_cnd.notify_all();
+    FrameMarkEnd("MainThreadConsumeLock");
 
     // Update the camera after the physics, so target lock is smooth
     std::size_t current_index = state.CurrentMassIndex();
diff --git a/src/physics.cpp b/src/physics.cpp
index 5bcb463..752bc93 100644
--- a/src/physics.cpp
+++ b/src/physics.cpp
@@ -201,12 +201,14 @@ auto ThreadedPhysics::PhysicsThread(ThreadedPhysics::PhysicsState &state)
     }
 
     // Physics update
+    // TODO: Respect thread-local deltatime + calculate UPS
     mass_springs.ClearForces();
     mass_springs.CalculateSpringForces();
     mass_springs.CalculateRepulsionForces();
     mass_springs.VerletUpdate(TIMESTEP * SIM_SPEED);
 
     // Publish the positions for the renderer (copy)
+    FrameMarkStart("PhysicsThreadProduceLock");
     {
       std::unique_lock<LockableBase(std::mutex)> lock(state.data_mtx);
       state.data_consumed_cnd.wait(
@@ -231,9 +233,10 @@ auto ThreadedPhysics::PhysicsThread(ThreadedPhysics::PhysicsState &state)
       state.data_ready = true;
       state.data_consumed = false;
     }
-
     // Notify the rendering thread that new data is available
     state.data_ready_cnd.notify_all();
+    FrameMarkEnd("PhysicsThreadProduceLock");
+
     FrameMarkEnd("PhysicsThread");
   }
 }
diff --git a/src/state.cpp b/src/state.cpp
index 048ae9c..805237d 100644
--- a/src/state.cpp
+++ b/src/state.cpp
@@ -6,6 +6,7 @@
 
 auto StateManager::LoadPreset(int preset) -> void {
   current_preset = preset;
+  current_state = CurrentGenerator()();
   ClearGraph();
   edited = false;
 }
@@ -49,11 +50,11 @@ auto StateManager::UpdateGraph() -> void {
   }
 
   if (!states.contains(current_state)) {
+    states.insert(std::make_pair(current_state, states.size()));
     physics.AddMassCmd();
     physics.AddSpringCmd(states.at(current_state), states.at(previous_state));
   }
 
-  states.insert(std::make_pair(current_state, states.size()));
   visited_states.insert(current_state);
   if (win_conditions[current_preset](current_state)) {
     winning_states.insert(current_state);
@@ -66,7 +67,6 @@ auto StateManager::ClearGraph() -> void {
   visited_states.clear();
   physics.ClearCmd();
 
-  current_state = CurrentGenerator()();
   states.insert(std::make_pair(current_state, states.size()));
   visited_states.insert(current_state);
   physics.AddMassCmd();