diff --git a/core/bind/core_bind.cpp b/core/bind/core_bind.cpp
index f9fb7d769530..01419607b3d3 100644
--- a/core/bind/core_bind.cpp
+++ b/core/bind/core_bind.cpp
@@ -2964,6 +2964,10 @@ float _Engine::get_physics_jitter_fix() const {
return Engine::get_singleton()->get_physics_jitter_fix();
}
+float _Engine::get_physics_interpolation_fraction() const {
+ return Engine::get_singleton()->get_physics_interpolation_fraction();
+}
+
void _Engine::set_target_fps(int p_fps) {
Engine::get_singleton()->set_target_fps(p_fps);
}
@@ -3052,6 +3056,7 @@ void _Engine::_bind_methods() {
ClassDB::bind_method(D_METHOD("get_iterations_per_second"), &_Engine::get_iterations_per_second);
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);
ClassDB::bind_method(D_METHOD("set_target_fps", "target_fps"), &_Engine::set_target_fps);
ClassDB::bind_method(D_METHOD("get_target_fps"), &_Engine::get_target_fps);
diff --git a/core/bind/core_bind.h b/core/bind/core_bind.h
index 3be5a0875289..f0f86e003f78 100644
--- a/core/bind/core_bind.h
+++ b/core/bind/core_bind.h
@@ -746,6 +746,7 @@ public:
void set_physics_jitter_fix(float p_threshold);
float get_physics_jitter_fix() const;
+ float get_physics_interpolation_fraction() const;
void set_target_fps(int p_fps);
int get_target_fps() const;
diff --git a/core/engine.cpp b/core/engine.cpp
index 2d8473fbd99d..0dd0459403b5 100644
--- a/core/engine.cpp
+++ b/core/engine.cpp
@@ -227,6 +227,7 @@ Engine::Engine() {
frames_drawn = 0;
ips = 60;
physics_jitter_fix = 0.5;
+ _physics_interpolation_fraction = 0.0f;
_frame_delay = 0;
_fps = 1;
_target_fps = 0;
diff --git a/core/engine.h b/core/engine.h
index 15665fee296d..192e8e67a098 100644
--- a/core/engine.h
+++ b/core/engine.h
@@ -63,6 +63,7 @@ private:
float _time_scale;
bool _pixel_snap;
uint64_t _physics_frames;
+ float _physics_interpolation_fraction;
uint64_t _idle_frames;
bool _in_physics;
@@ -95,6 +96,7 @@ public:
bool is_in_physics_frame() const { return _in_physics; }
uint64_t get_idle_frame_ticks() const { return _frame_ticks; }
float get_idle_frame_step() const { return _frame_step; }
+ float get_physics_interpolation_fraction() const { return _physics_interpolation_fraction; }
void set_time_scale(float p_scale);
float get_time_scale() const;
diff --git a/doc/classes/Engine.xml b/doc/classes/Engine.xml
index 60a807c30473..187e13d7bda7 100644
--- a/doc/classes/Engine.xml
+++ b/doc/classes/Engine.xml
@@ -72,6 +72,13 @@
Returns the main loop object (see [MainLoop] and [SceneTree]).
+
+
+
+
+ Returns the fraction through the current physics tick we are at the time of rendering the frame. This can be used to implement fixed timestep interpolation.
+
+
diff --git a/main/main.cpp b/main/main.cpp
index 3f84eca1d276..d3e816eb482b 100644
--- a/main/main.cpp
+++ b/main/main.cpp
@@ -1869,6 +1869,7 @@ bool Main::iteration() {
double scaled_step = step * time_scale;
Engine::get_singleton()->_frame_step = step;
+ Engine::get_singleton()->_physics_interpolation_fraction = advance.interpolation_fraction;
uint64_t physics_process_ticks = 0;
uint64_t idle_process_ticks = 0;
diff --git a/main/main_timer_sync.cpp b/main/main_timer_sync.cpp
index f7388c851787..edacb20f28b3 100644
--- a/main/main_timer_sync.cpp
+++ b/main/main_timer_sync.cpp
@@ -178,6 +178,10 @@ MainFrameTime MainTimerSync::advance_checked(float p_frame_slice, int p_iteratio
// track deficit
time_deficit = p_idle_step - ret.idle_step;
+ // p_frame_slice is 1.0 / iterations_per_sec
+ // i.e. the time in seconds taken by a physics tick
+ ret.interpolation_fraction = time_accum / p_frame_slice;
+
return ret;
}
diff --git a/main/main_timer_sync.h b/main/main_timer_sync.h
index 179119edce1c..93d335b27f08 100644
--- a/main/main_timer_sync.h
+++ b/main/main_timer_sync.h
@@ -36,6 +36,7 @@
struct MainFrameTime {
float idle_step; // time to advance idles for (argument to process())
int physics_steps; // number of times to iterate the physics engine
+ float interpolation_fraction; // fraction through the current physics tick
void clamp_idle(float min_idle_step, float max_idle_step);
};