Merge pull request #65836 from Calinou/add-max-physics-steps-per-frame-setting

Implement adjusting the maximum number of physics steps per rendered frame

2 files changed, 9 insertions, 2 deletions

diff --git a/doc/classes/Engine.xml b/doc/classes/Engine.xml
index 821fae37a6..d583e07f59 100644
--- a/doc/classes/Engine.xml
+++ b/doc/classes/Engine.xml
@@ -275,13 +275,16 @@
 			If [member ProjectSettings.display/window/vsync/vsync_mode] is [code]Disabled[/code], limiting the FPS to a high value that can be consistently reached on the system can reduce input lag compared to an uncapped framerate. Since this works by ensuring the GPU load is lower than 100%, this latency reduction is only effective in GPU-bottlenecked scenarios, not CPU-bottlenecked scenarios.
 			See also [member physics_ticks_per_second] and [member ProjectSettings.application/run/max_fps].
 		</member>
+		<member name="max_physics_steps_per_frame" type="int" setter="set_max_physics_steps_per_frame" getter="get_max_physics_steps_per_frame" default="8">
+			Controls the maximum number of physics steps that can be simulated each rendered frame. The default value is tuned to avoid "spiral of death" situations where expensive physics simulations trigger more expensive simulations indefinitely. However, the game will appear to slow down if the rendering FPS is less than [code]1 / max_physics_steps_per_frame[/code] of [member physics_ticks_per_second]. This occurs even if [code]delta[/code] is consistently used in physics calculations. To avoid this, increase [member max_physics_steps_per_frame] if you have increased [member physics_ticks_per_second] significantly above its default value.
+		</member>
 		<member name="physics_jitter_fix" type="float" setter="set_physics_jitter_fix" getter="get_physics_jitter_fix" default="0.5">
 			Controls how much physics ticks are synchronized with real time. For 0 or less, the ticks are synchronized. Such values are recommended for network games, where clock synchronization matters. Higher values cause higher deviation of the in-game clock and real clock but smooth out framerate jitters. The default value of 0.5 should be fine for most; values above 2 could cause the game to react to dropped frames with a noticeable delay and are not recommended.
 			[b]Note:[/b] For best results, when using a custom physics interpolation solution, the physics jitter fix should be disabled by setting [member physics_jitter_fix] to [code]0[/code].
 		</member>
 		<member name="physics_ticks_per_second" type="int" setter="set_physics_ticks_per_second" getter="get_physics_ticks_per_second" default="60">
 			The number of fixed iterations per second. This controls how often physics simulation and [method Node._physics_process] methods are run. This value should generally always be set to [code]60[/code] or above, as Godot doesn't interpolate the physics step. As a result, values lower than [code]60[/code] will look stuttery. This value can be increased to make input more reactive or work around collision tunneling issues, but keep in mind doing so will increase CPU usage. See also [member max_fps] and [member ProjectSettings.physics/common/physics_ticks_per_second].
-			[b]Note:[/b] Only 8 physics ticks may be simulated per rendered frame at most. If more than 8 physics ticks have to be simulated per rendered frame to keep up with rendering, the game will appear to slow down (even if [code]delta[/code] is used consistently in physics calculations). Therefore, it is recommended not to increase [member physics_ticks_per_second] above 240. Otherwise, the game will slow down when the rendering framerate goes below 30 FPS.
+			[b]Note:[/b] Only [member max_physics_steps_per_frame] physics ticks may be simulated per rendered frame at most. If more physics ticks have to be simulated per rendered frame to keep up with rendering, the project will appear to slow down (even if [code]delta[/code] is used consistently in physics calculations). Therefore, it is recommended to also increase [member max_physics_steps_per_frame] if increasing [member physics_ticks_per_second] significantly above its default value.
 		</member>
 		<member name="print_error_messages" type="bool" setter="set_print_error_messages" getter="is_printing_error_messages" default="true">
 			If [code]false[/code], stops printing error and warning messages to the console and editor Output log. This can be used to hide error and warning messages during unit test suite runs. This property is equivalent to the [member ProjectSettings.application/run/disable_stderr] project setting.
diff --git a/doc/classes/ProjectSettings.xml b/doc/classes/ProjectSettings.xml
index 9990b38925..fe6f384603 100644
--- a/doc/classes/ProjectSettings.xml
+++ b/doc/classes/ProjectSettings.xml
@@ -1812,6 +1812,10 @@
 		<member name="physics/common/enable_object_picking" type="bool" setter="" getter="" default="true">
 			Enables [member Viewport.physics_object_picking] on the root viewport.
 		</member>
+		<member name="physics/common/max_physics_steps_per_frame" type="int" setter="" getter="" default="8">
+			Controls the maximum number of physics steps that can be simulated each rendered frame. The default value is tuned to avoid "spiral of death" situations where expensive physics simulations trigger more expensive simulations indefinitely. However, the game will appear to slow down if the rendering FPS is less than [code]1 / max_physics_steps_per_frame[/code] of [member physics/common/physics_ticks_per_second]. This occurs even if [code]delta[/code] is consistently used in physics calculations. To avoid this, increase [member physics/common/max_physics_steps_per_frame] if you have increased [member physics/common/physics_ticks_per_second] significantly above its default value.
+			[b]Note:[/b] This property is only read when the project starts. To change the maximum number of simulated physics steps per frame at runtime, set [member Engine.max_physics_steps_per_frame] instead.
+		</member>
 		<member name="physics/common/physics_jitter_fix" type="float" setter="" getter="" default="0.5">
 			Controls how much physics ticks are synchronized with real time. For 0 or less, the ticks are synchronized. Such values are recommended for network games, where clock synchronization matters. Higher values cause higher deviation of in-game clock and real clock, but allows smoothing out framerate jitters. The default value of 0.5 should be fine for most; values above 2 could cause the game to react to dropped frames with a noticeable delay and are not recommended.
 			[b]Note:[/b] For best results, when using a custom physics interpolation solution, the physics jitter fix should be disabled by setting [member physics/common/physics_jitter_fix] to [code]0[/code].
@@ -1820,7 +1824,7 @@
 		<member name="physics/common/physics_ticks_per_second" type="int" setter="" getter="" default="60">
 			The number of fixed iterations per second. This controls how often physics simulation and [method Node._physics_process] methods are run. See also [member application/run/max_fps].
 			[b]Note:[/b] This property is only read when the project starts. To change the physics FPS at runtime, set [member Engine.physics_ticks_per_second] instead.
-			[b]Note:[/b] Only 8 physics ticks may be simulated per rendered frame at most. If more than 8 physics ticks have to be simulated per rendered frame to keep up with rendering, the game will appear to slow down (even if [code]delta[/code] is used consistently in physics calculations). Therefore, it is recommended not to increase [member physics/common/physics_ticks_per_second] above 240. Otherwise, the game will slow down when the rendering framerate goes below 30 FPS.
+			[b]Note:[/b] Only [member physics/common/max_physics_steps_per_frame] physics ticks may be simulated per rendered frame at most. If more physics ticks have to be simulated per rendered frame to keep up with rendering, the project will appear to slow down (even if [code]delta[/code] is used consistently in physics calculations). Therefore, it is recommended to also increase [member physics/common/max_physics_steps_per_frame] if increasing [member physics/common/physics_ticks_per_second] significantly above its default value.
 		</member>
 		<member name="rendering/2d/sdf/oversize" type="int" setter="" getter="" default="1">
 		</member>