1 files changed, 104 insertions, 0 deletions
diff --git a/scene/3d/spatial_velocity_tracker.cpp b/scene/3d/spatial_velocity_tracker.cpp
new file mode 100644
index 0000000000..dc822d0446
--- /dev/null
+++ b/scene/3d/spatial_velocity_tracker.cpp
@@ -0,0 +1,104 @@
+#include "spatial_velocity_tracker.h"
+#include "engine.h"
+
+void SpatialVelocityTracker::set_track_fixed_step(bool p_track_fixed_step) {
+
+	fixed_step = p_track_fixed_step;
+}
+
+bool SpatialVelocityTracker::is_tracking_fixed_step() const {
+
+	return fixed_step;
+}
+void SpatialVelocityTracker::update_position(const Vector3 &p_position) {
+
+	PositionHistory ph;
+	ph.position = p_position;
+	if (fixed_step) {
+		ph.frame = Engine::get_singleton()->get_fixed_frames();
+	} else {
+		ph.frame = Engine::get_singleton()->get_idle_frame_ticks();
+	}
+
+	if (position_history_len == 0 || position_history[0].frame != ph.frame) { //in same frame, use latest
+		position_history_len = MIN(position_history.size(), position_history_len + 1);
+		for (int i = position_history_len - 1; i > 0; i--) {
+			position_history[i] = position_history[i - 1];
+		}
+	}
+
+	position_history[0] = ph;
+}
+Vector3 SpatialVelocityTracker::get_tracked_linear_velocity() const {
+
+	Vector3 linear_velocity;
+
+	float max_time = 1 / 5.0; //maximum time to interpolate a velocity
+
+	Vector3 distance_accum;
+	float time_accum = 0.0;
+	float base_time = 0.0;
+
+	if (position_history_len) {
+		if (fixed_step) {
+			uint64_t base = Engine::get_singleton()->get_fixed_frames();
+			base_time = float(base - position_history[0].frame) / Engine::get_singleton()->get_iterations_per_second();
+		} else {
+			uint64_t base = Engine::get_singleton()->get_idle_frame_ticks();
+			base_time = double(base - position_history[0].frame) / 1000000.0;
+		}
+	}
+
+	for (int i = 0; i < position_history_len - 1; i++) {
+		float delta = 0.0;
+		uint64_t diff = position_history[i].frame - position_history[i + 1].frame;
+		Vector3 distance = position_history[i].position - position_history[i + 1].position;
+
+		if (fixed_step) {
+			delta = float(diff) / Engine::get_singleton()->get_iterations_per_second();
+		} else {
+			delta = double(diff) / 1000000.0;
+		}
+
+		if (base_time + time_accum + delta > max_time)
+			break;
+
+		distance_accum += distance;
+		time_accum += delta;
+	}
+
+	if (time_accum) {
+		linear_velocity = distance_accum / time_accum;
+	}
+
+	return linear_velocity;
+}
+
+void SpatialVelocityTracker::reset(const Vector3 &p_new_pos) {
+
+	PositionHistory ph;
+	ph.position = p_new_pos;
+	if (fixed_step) {
+		ph.frame = Engine::get_singleton()->get_fixed_frames();
+	} else {
+		ph.frame = Engine::get_singleton()->get_idle_frame_ticks();
+	}
+
+	position_history[0] = ph;
+	position_history_len = 1;
+}
+
+void SpatialVelocityTracker::_bind_methods() {
+
+	ClassDB::bind_method(D_METHOD("set_track_fixed_step", "enable"), &SpatialVelocityTracker::set_track_fixed_step);
+	ClassDB::bind_method(D_METHOD("is_tracking_fixed_step"), &SpatialVelocityTracker::is_tracking_fixed_step);
+	ClassDB::bind_method(D_METHOD("update_position", "position"), &SpatialVelocityTracker::update_position);
+	ClassDB::bind_method(D_METHOD("get_tracked_linear_velocity"), &SpatialVelocityTracker::get_tracked_linear_velocity);
+	ClassDB::bind_method(D_METHOD("reset", "position"), &SpatialVelocityTracker::reset);
+}
+
+SpatialVelocityTracker::SpatialVelocityTracker() {
+	position_history.resize(4); // should be configurable
+	position_history_len = 0;
+	fixed_step = false;
+}