Add frame delta smoothing option

core/bind/core_bind.cpp

@@ -596,6 +596,14 @@ bool _OS::is_vsync_via_compositor_enabled() const {
 	return OS::get_singleton()->is_vsync_via_compositor_enabled();
 }
 
+void _OS::set_delta_smoothing(bool p_enabled) {
+	OS::get_singleton()->set_delta_smoothing(p_enabled);
+}
+
+bool _OS::is_delta_smoothing_enabled() const {
+	return OS::get_singleton()->is_delta_smoothing_enabled();
+}
+
 _OS::PowerState _OS::get_power_state() {
 	return _OS::PowerState(OS::get_singleton()->get_power_state());
 }
@@ -1369,6 +1377,9 @@ void _OS::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_vsync_via_compositor", "enable"), &_OS::set_vsync_via_compositor);
 	ClassDB::bind_method(D_METHOD("is_vsync_via_compositor_enabled"), &_OS::is_vsync_via_compositor_enabled);
 
+	ClassDB::bind_method(D_METHOD("set_delta_smoothing", "delta_smoothing_enabled"), &_OS::set_delta_smoothing);
+	ClassDB::bind_method(D_METHOD("is_delta_smoothing_enabled"), &_OS::is_delta_smoothing_enabled);
+
 	ClassDB::bind_method(D_METHOD("has_feature", "tag_name"), &_OS::has_feature);
 
 	ClassDB::bind_method(D_METHOD("get_power_state"), &_OS::get_power_state);
@@ -1391,6 +1402,7 @@ void _OS::_bind_methods() {
 	ADD_PROPERTY(PropertyInfo(Variant::INT, "exit_code"), "set_exit_code", "get_exit_code");
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "vsync_enabled"), "set_use_vsync", "is_vsync_enabled");
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "vsync_via_compositor"), "set_vsync_via_compositor", "is_vsync_via_compositor_enabled");
+	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "delta_smoothing"), "set_delta_smoothing", "is_delta_smoothing_enabled");
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "low_processor_usage_mode"), "set_low_processor_usage_mode", "is_in_low_processor_usage_mode");
 	ADD_PROPERTY(PropertyInfo(Variant::INT, "low_processor_usage_mode_sleep_usec"), "set_low_processor_usage_mode_sleep_usec", "get_low_processor_usage_mode_sleep_usec");
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "keep_screen_on"), "set_keep_screen_on", "is_keep_screen_on");

core/bind/core_bind.h

@@ -374,6 +374,9 @@ class _OS : public Object {
 	void set_vsync_via_compositor(bool p_enable);
 	bool is_vsync_via_compositor_enabled() const;
 
+	void set_delta_smoothing(bool p_enabled);
+	bool is_delta_smoothing_enabled() const;
+
 	PowerState get_power_state();
 	int get_power_seconds_left();
 	int get_power_percent_left();

core/os/os.cpp

@@ -587,6 +587,14 @@ bool OS::is_vsync_via_compositor_enabled() const {
 	return _vsync_via_compositor;
 }
 
+void OS::set_delta_smoothing(bool p_enabled) {
+	_delta_smoothing_enabled = p_enabled;
+}
+
+bool OS::is_delta_smoothing_enabled() const {
+	return _delta_smoothing_enabled;
+}
+
 OS::PowerState OS::get_power_state() {
 	return POWERSTATE_UNKNOWN;
 }
@@ -798,6 +806,7 @@ OS::OS() {
 	_no_window = false;
 	_exit_code = 0;
 	_orientation = SCREEN_LANDSCAPE;
+	_delta_smoothing_enabled = false;
 
 	_render_thread_mode = RENDER_THREAD_SAFE;
 

core/os/os.h

@@ -62,6 +62,7 @@ class OS {
 	bool _allow_layered;
 	bool _use_vsync;
 	bool _vsync_via_compositor;
+	bool _delta_smoothing_enabled;
 
 	char *last_error;
 
@@ -548,6 +549,9 @@ class OS {
 	void set_vsync_via_compositor(bool p_enable);
 	bool is_vsync_via_compositor_enabled() const;
 
+	void set_delta_smoothing(bool p_enabled);
+	bool is_delta_smoothing_enabled() const;
+
 	virtual OS::PowerState get_power_state();
 	virtual int get_power_seconds_left();
 	virtual int get_power_percent_left();

doc/classes/OS.xml

@@ -1104,6 +1104,9 @@
 		<member name="current_screen" type="int" setter="set_current_screen" getter="get_current_screen" default="0">
 			The current screen index (starting from 0).
 		</member>
+		<member name="delta_smoothing" type="bool" setter="set_delta_smoothing" getter="is_delta_smoothing_enabled" default="true">
+			If [code]true[/code], the engine filters the time delta measured between each frame, and attempts to compensate for random variation. This will only operate on systems where V-Sync is active.
+		</member>
 		<member name="exit_code" type="int" setter="set_exit_code" getter="get_exit_code" default="0">
 			The exit code passed to the OS when the main loop exits. By convention, an exit code of [code]0[/code] indicates success whereas a non-zero exit code indicates an error. For portability reasons, the exit code should be set between 0 and 125 (inclusive).
 			[b]Note:[/b] This value will be ignored if using [method SceneTree.quit] with an [code]exit_code[/code] argument passed.

doc/classes/ProjectSettings.xml

@@ -244,6 +244,11 @@
 		<member name="application/config/windows_native_icon" type="String" setter="" getter="" default="&quot;&quot;">
 			Icon set in [code].ico[/code] format used on Windows to set the game's icon. This is done automatically on start by calling [method OS.set_native_icon].
 		</member>
+		<member name="application/run/delta_smoothing" type="bool" setter="" getter="" default="true">
+			Time samples for frame deltas are subject to random variation introduced by the platform, even when frames are displayed at regular intervals thanks to V-Sync. This can lead to jitter. Delta smoothing can often give a better result by filtering the input deltas to correct for minor fluctuations from the refresh rate.
+			[b]Note:[/b] Delta smoothing is only attempted when [member display/window/vsync/use_vsync] is switched on, as it does not work well without V-Sync.
+			It may take several seconds at a stable frame rate before the smoothing is initially activated. It will only be active on machines where performance is adequate to render frames at the refresh rate.
+		</member>
 		<member name="application/run/disable_stderr" type="bool" setter="" getter="" default="false">
 			If [code]true[/code], disables printing to standard error. If [code]true[/code], this also hides error and warning messages printed by [method @GDScript.push_error] and [method @GDScript.push_warning]. See also [member application/run/disable_stdout].
 			Changes to this setting will only be applied upon restarting the application.

main/main.cpp

@@ -267,6 +267,8 @@ void Main::print_help(const char *p_binary) {
 	OS::get_singleton()->print("  --no-window                      Run with invisible window. Useful together with --script.\n");
 	OS::get_singleton()->print("  --enable-vsync-via-compositor    When vsync is enabled, vsync via the OS' window compositor (Windows only).\n");
 	OS::get_singleton()->print("  --disable-vsync-via-compositor   Disable vsync via the OS' window compositor (Windows only).\n");
+	OS::get_singleton()->print("  --enable-delta-smoothing         When vsync is enabled, enabled frame delta smoothing.\n");
+	OS::get_singleton()->print("  --disable-delta-smoothing        Disable frame delta smoothing.\n");
 	OS::get_singleton()->print("  --tablet-driver                  Tablet input driver (");
 	for (int i = 0; i < OS::get_singleton()->get_tablet_driver_count(); i++) {
 		if (i != 0) {
@@ -417,6 +419,7 @@ Error Main::setup(const char *execpath, int argc, char *argv[], bool p_second_ph
 	bool use_custom_res = true;
 	bool force_res = false;
 	bool saw_vsync_via_compositor_override = false;
+	bool delta_smoothing_override = false;
 #ifdef TOOLS_ENABLED
 	bool found_project = false;
 #endif
@@ -637,6 +640,12 @@ Error Main::setup(const char *execpath, int argc, char *argv[], bool p_second_ph
 		} else if (I->get() == "--disable-vsync-via-compositor") {
 			video_mode.vsync_via_compositor = false;
 			saw_vsync_via_compositor_override = true;
+		} else if (I->get() == "--enable-delta-smoothing") {
+			OS::get_singleton()->set_delta_smoothing(true);
+			delta_smoothing_override = true;
+		} else if (I->get() == "--disable-delta-smoothing") {
+			OS::get_singleton()->set_delta_smoothing(false);
+			delta_smoothing_override = true;
 #endif
 		} else if (I->get() == "--profiling") { // enable profiling
 
@@ -1191,6 +1200,11 @@ Error Main::setup(const char *execpath, int argc, char *argv[], bool p_second_ph
 	OS::get_singleton()->set_low_processor_usage_mode_sleep_usec(GLOBAL_DEF("application/run/low_processor_mode_sleep_usec", 6900)); // Roughly 144 FPS
 	ProjectSettings::get_singleton()->set_custom_property_info("application/run/low_processor_mode_sleep_usec", PropertyInfo(Variant::INT, "application/run/low_processor_mode_sleep_usec", PROPERTY_HINT_RANGE, "0,33200,1,or_greater")); // No negative numbers
 
+	GLOBAL_DEF("application/run/delta_smoothing", true);
+	if (!delta_smoothing_override) {
+		OS::get_singleton()->set_delta_smoothing(GLOBAL_GET("application/run/delta_smoothing"));
+	}
+
 	GLOBAL_DEF("display/window/ios/hide_home_indicator", true);
 	GLOBAL_DEF("input_devices/pointing/ios/touch_delay", 0.150);