Implement adjusting the maximum number of physics steps per rendered frame

When using high physics FPS (which is a requirement to minimize input
lag and improve precision in simulation racing games), a higher value
prevents the game from slowing down at low rendering FPS.

This can be done via an Engine property for run-time changes,
or a project setting for initial changes.

4 files changed, 27 insertions, 0 deletions

diff --git a/core/config/engine.cpp b/core/config/engine.cpp
index 21e910be5b..7aa5f4d06d 100644
--- a/core/config/engine.cpp
+++ b/core/config/engine.cpp
@@ -48,6 +48,15 @@ int Engine::get_physics_ticks_per_second() const {
 	return ips;
 }
 
+void Engine::set_max_physics_steps_per_frame(int p_max_physics_steps) {
+	ERR_FAIL_COND_MSG(p_max_physics_steps <= 0, "Maximum number of physics steps per frame must be greater than 0.");
+	max_physics_steps_per_frame = p_max_physics_steps;
+}
+
+int Engine::get_max_physics_steps_per_frame() const {
+	return max_physics_steps_per_frame;
+}
+
 void Engine::set_physics_jitter_fix(double p_threshold) {
 	if (p_threshold < 0) {
 		p_threshold = 0;
diff --git a/core/config/engine.h b/core/config/engine.h
index 21517e46b7..1b179c5727 100644
--- a/core/config/engine.h
+++ b/core/config/engine.h
@@ -63,6 +63,7 @@ private:
 	int _max_fps = 0;
 	double _time_scale = 1.0;
 	uint64_t _physics_frames = 0;
+	int max_physics_steps_per_frame = 8;
 	double _physics_interpolation_fraction = 0.0f;
 	bool abort_on_gpu_errors = false;
 	bool use_validation_layers = false;
@@ -93,6 +94,9 @@ public:
 	virtual void set_physics_ticks_per_second(int p_ips);
 	virtual int get_physics_ticks_per_second() const;
 
+	virtual void set_max_physics_steps_per_frame(int p_max_physics_steps);
+	virtual int get_max_physics_steps_per_frame() const;
+
 	void set_physics_jitter_fix(double p_threshold);
 	double get_physics_jitter_fix() const;
 
diff --git a/core/core_bind.cpp b/core/core_bind.cpp
index 7496ba1979..5c4ed9e483 100644
--- a/core/core_bind.cpp
+++ b/core/core_bind.cpp
@@ -1471,6 +1471,14 @@ int Engine::get_physics_ticks_per_second() const {
 	return ::Engine::get_singleton()->get_physics_ticks_per_second();
 }
 
+void Engine::set_max_physics_steps_per_frame(int p_max_physics_steps) {
+	::Engine::get_singleton()->set_max_physics_steps_per_frame(p_max_physics_steps);
+}
+
+int Engine::get_max_physics_steps_per_frame() const {
+	return ::Engine::get_singleton()->get_max_physics_steps_per_frame();
+}
+
 void Engine::set_physics_jitter_fix(double p_threshold) {
 	::Engine::get_singleton()->set_physics_jitter_fix(p_threshold);
 }
@@ -1622,6 +1630,8 @@ bool Engine::is_printing_error_messages() const {
 void Engine::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_physics_ticks_per_second", "physics_ticks_per_second"), &Engine::set_physics_ticks_per_second);
 	ClassDB::bind_method(D_METHOD("get_physics_ticks_per_second"), &Engine::get_physics_ticks_per_second);
+	ClassDB::bind_method(D_METHOD("set_max_physics_steps_per_frame", "max_physics_steps"), &Engine::set_max_physics_steps_per_frame);
+	ClassDB::bind_method(D_METHOD("get_max_physics_steps_per_frame"), &Engine::get_max_physics_steps_per_frame);
 	ClassDB::bind_method(D_METHOD("set_physics_jitter_fix", "physics_jitter_fix"), &Engine::set_physics_jitter_fix);
 	ClassDB::bind_method(D_METHOD("get_physics_jitter_fix"), &Engine::get_physics_jitter_fix);
 	ClassDB::bind_method(D_METHOD("get_physics_interpolation_fraction"), &Engine::get_physics_interpolation_fraction);
@@ -1669,6 +1679,7 @@ void Engine::_bind_methods() {
 
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "print_error_messages"), "set_print_error_messages", "is_printing_error_messages");
 	ADD_PROPERTY(PropertyInfo(Variant::INT, "physics_ticks_per_second"), "set_physics_ticks_per_second", "get_physics_ticks_per_second");
+	ADD_PROPERTY(PropertyInfo(Variant::INT, "max_physics_steps_per_frame"), "set_max_physics_steps_per_frame", "get_max_physics_steps_per_frame");
 	ADD_PROPERTY(PropertyInfo(Variant::INT, "max_fps"), "set_max_fps", "get_max_fps");
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "time_scale"), "set_time_scale", "get_time_scale");
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "physics_jitter_fix"), "set_physics_jitter_fix", "get_physics_jitter_fix");
diff --git a/core/core_bind.h b/core/core_bind.h
index 9261698076..5c7702be0b 100644
--- a/core/core_bind.h
+++ b/core/core_bind.h
@@ -484,6 +484,9 @@ public:
 	void set_physics_ticks_per_second(int p_ips);
 	int get_physics_ticks_per_second() const;
 
+	void set_max_physics_steps_per_frame(int p_max_physics_steps);
+	int get_max_physics_steps_per_frame() const;
+
 	void set_physics_jitter_fix(double p_threshold);
 	double get_physics_jitter_fix() const;
 	double get_physics_interpolation_fraction() const;