2D Fixed Timestep Interpolation

Adds support to canvas items and Camera2D.
godotengine · Aug 1, 2023 · 5162efb · 5162efb
1 parent ac5d7dc
commit 5162efb
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Showing 30 changed files with 739 additions and 140 deletions.
diff --git a/core/math/transform_interpolator.cpp b/core/math/transform_interpolator.cpp
@@ -30,6 +30,51 @@
 
 #include "transform_interpolator.h"
 
+#include "core/math/transform_2d.h"
+
+void TransformInterpolator::interpolate_transform_2d(const Transform2D &p_prev, const Transform2D &p_curr, Transform2D &r_result, real_t p_fraction) {
+	// Extract parameters.
+	Vector2 p1 = p_prev.get_origin();
+	Vector2 p2 = p_curr.get_origin();
+
+	// Special case for physics interpolation, if flipping, don't interpolate basis.
+	// If the determinant polarity changes, the handedness of the coordinate system changes.
+	if (_sign(p_prev.determinant()) != _sign(p_curr.determinant())) {
+		r_result.elements[0] = p_curr.elements[0];
+		r_result.elements[1] = p_curr.elements[1];
+		r_result.set_origin(Vector2::linear_interpolate(p1, p2, p_fraction));
+		return;
+	}
+
+	real_t r1 = p_prev.get_rotation();
+	real_t r2 = p_curr.get_rotation();
+
+	Size2 s1 = p_prev.get_scale();
+	Size2 s2 = p_curr.get_scale();
+
+	// Slerp rotation.
+	Vector2 v1(Math::cos(r1), Math::sin(r1));
+	Vector2 v2(Math::cos(r2), Math::sin(r2));
+
+	real_t dot = v1.dot(v2);
+
+	dot = CLAMP(dot, -1, 1);
+
+	Vector2 v;
+
+	if (dot > 0.9995f) {
+		v = Vector2::linear_interpolate(v1, v2, p_fraction).normalized(); // Linearly interpolate to avoid numerical precision issues.
+	} else {
+		real_t angle = p_fraction * Math::acos(dot);
+		Vector2 v3 = (v2 - v1 * dot).normalized();
+		v = v1 * Math::cos(angle) + v3 * Math::sin(angle);
+	}
+
+	// Construct matrix.
+	r_result = Transform2D(Math::atan2(v.y, v.x), Vector2::linear_interpolate(p1, p2, p_fraction));
+	r_result.scale_basis(Vector2::linear_interpolate(s1, s2, p_fraction));
+}
+
 void TransformInterpolator::interpolate_transform(const Transform &p_prev, const Transform &p_curr, Transform &r_result, real_t p_fraction) {
 	r_result.origin = p_prev.origin + ((p_curr.origin - p_prev.origin) * p_fraction);
 	interpolate_basis(p_prev.basis, p_curr.basis, r_result.basis, p_fraction);

diff --git a/core/math/transform_interpolator.h b/core/math/transform_interpolator.h
@@ -46,7 +46,7 @@
 // several frames may occur between each physics tick, which will make it cheaper
 // than performing every frame.
 
-class Transform;
+struct Transform2D;
 
 class TransformInterpolator {
 public:
@@ -66,6 +66,7 @@ class TransformInterpolator {
 	static Quat _basis_to_quat_unchecked(const Basis &p_basis);
 	static bool _basis_is_orthogonal(const Basis &p_basis, real_t p_epsilon = 0.01f);
 	static bool _basis_is_orthogonal_any_scale(const Basis &p_basis);
+	static bool _sign(real_t p_val) { return p_val >= 0; }
 
 	static void interpolate_basis_linear(const Basis &p_prev, const Basis &p_curr, Basis &r_result, real_t p_fraction);
 	static void interpolate_basis_scaled_slerp(Basis p_prev, Basis p_curr, Basis &r_result, real_t p_fraction);
@@ -75,6 +76,7 @@ class TransformInterpolator {
 	// These will be slower.
 	static void interpolate_transform(const Transform &p_prev, const Transform &p_curr, Transform &r_result, real_t p_fraction);
 	static void interpolate_basis(const Basis &p_prev, const Basis &p_curr, Basis &r_result, real_t p_fraction);
+	static void interpolate_transform_2d(const Transform2D &p_prev, const Transform2D &p_curr, Transform2D &r_result, real_t p_fraction);
 
 	// Optimized function when you know ahead of time the method
 	static void interpolate_transform_via_method(const Transform &p_prev, const Transform &p_curr, Transform &r_result, real_t p_fraction, Method p_method);

diff --git a/core/os/main_loop.h b/core/os/main_loop.h
@@ -67,6 +67,7 @@ class MainLoop : public Object {
 	virtual void input_text(const String &p_text);
 
 	virtual void init();
+	virtual void iteration_prepare() {}
 	virtual bool iteration(float p_time);
 	virtual void iteration_end() {}
 	virtual bool idle(float p_time);

diff --git a/doc/classes/Control.xml b/doc/classes/Control.xml
@@ -825,6 +825,7 @@
 		<member name="mouse_filter" type="int" setter="set_mouse_filter" getter="get_mouse_filter" enum="Control.MouseFilter" default="0">
 			Controls whether the control will be able to receive mouse button input events through [method _gui_input] and how these events should be handled. Also controls whether the control can receive the [signal mouse_entered], and [signal mouse_exited] signals. See the constants to learn what each does.
 		</member>
+		<member name="physics_interpolation_mode" type="int" setter="set_physics_interpolation_mode" getter="get_physics_interpolation_mode" overrides="Node" enum="Node.PhysicsInterpolationMode" default="1" />
 		<member name="rect_clip_content" type="bool" setter="set_clip_contents" getter="is_clipping_contents" default="false">
 			Enables whether rendering of [CanvasItem] based children should be clipped to this control's rectangle. If [code]true[/code], parts of a child which would be visibly outside of this control's rectangle will not be rendered.
 		</member>

diff --git a/doc/classes/ParallaxLayer.xml b/doc/classes/ParallaxLayer.xml
@@ -23,6 +23,7 @@
 		<member name="motion_scale" type="Vector2" setter="set_motion_scale" getter="get_motion_scale" default="Vector2( 1, 1 )">
 			Multiplies the ParallaxLayer's motion. If an axis is set to [code]0[/code], it will not scroll.
 		</member>
+		<member name="physics_interpolation_mode" type="int" setter="set_physics_interpolation_mode" getter="get_physics_interpolation_mode" overrides="Node" enum="Node.PhysicsInterpolationMode" default="1" />
 	</members>
 	<constants>
 	</constants>

diff --git a/doc/classes/VisualServer.xml b/doc/classes/VisualServer.xml
@@ -325,6 +325,14 @@
 				Once finished with your RID, you will want to free the RID using the VisualServer's [method free_rid] static method.
 			</description>
 		</method>
+		<method name="canvas_item_reset_physics_interpolation">
+			<return type="void" />
+			<argument index="0" name="item" type="RID" />
+			<description>
+				Prevents physics interpolation for the current physics tick.
+				This is useful when moving a canvas item to a new location, to give an instantaneous change rather than interpolation from the previous location.
+			</description>
+		</method>
 		<method name="canvas_item_set_clip">
 			<return type="void" />
 			<argument index="0" name="item" type="RID" />
@@ -375,6 +383,14 @@
 				Sets the index for the [CanvasItem].
 			</description>
 		</method>
+		<method name="canvas_item_set_interpolated">
+			<return type="void" />
+			<argument index="0" name="item" type="RID" />
+			<argument index="1" name="interpolated" type="bool" />
+			<description>
+				Turns on and off physics interpolation for the canvas item.
+			</description>
+		</method>
 		<method name="canvas_item_set_light_mask">
 			<return type="void" />
 			<argument index="0" name="item" type="RID" />
@@ -463,6 +479,16 @@
 				Sets the [CanvasItem]'s Z index, i.e. its draw order (lower indexes are drawn first).
 			</description>
 		</method>
+		<method name="canvas_item_transform_physics_interpolation">
+			<return type="void" />
+			<argument index="0" name="item" type="RID" />
+			<argument index="1" name="xform" type="Transform2D" />
+			<description>
+				Transforms both the current and previous stored transform for a canvas item.
+				This allows transforming a canvas item without creating a "glitch" in the interpolation.
+				This is particularly useful for large worlds utilising a shifting origin.
+			</description>
+		</method>
 		<method name="canvas_light_attach_to_canvas">
 			<return type="void" />
 			<argument index="0" name="light" type="RID" />
@@ -493,6 +519,14 @@
 				Once finished with your RID, you will want to free the RID using the VisualServer's [method free_rid] static method.
 			</description>
 		</method>
+		<method name="canvas_light_occluder_reset_physics_interpolation">
+			<return type="void" />
+			<argument index="0" name="occluder" type="RID" />
+			<description>
+				Prevents physics interpolation for the current physics tick.
+				This is useful when moving an occluder to a new location, to give an instantaneous change rather than interpolation from the previous location.
+			</description>
+		</method>
 		<method name="canvas_light_occluder_set_enabled">
 			<return type="void" />
 			<argument index="0" name="occluder" type="RID" />
@@ -501,6 +535,14 @@
 				Enables or disables light occluder.
 			</description>
 		</method>
+		<method name="canvas_light_occluder_set_interpolated">
+			<return type="void" />
+			<argument index="0" name="occluder" type="RID" />
+			<argument index="1" name="interpolated" type="bool" />
+			<description>
+				Turns on and off physics interpolation for the occluder.
+			</description>
+		</method>
 		<method name="canvas_light_occluder_set_light_mask">
 			<return type="void" />
 			<argument index="0" name="occluder" type="RID" />
@@ -525,6 +567,24 @@
 				Sets a light occluder's [Transform2D].
 			</description>
 		</method>
+		<method name="canvas_light_occluder_transform_physics_interpolation">
+			<return type="void" />
+			<argument index="0" name="occluder" type="RID" />
+			<argument index="1" name="xform" type="Transform2D" />
+			<description>
+				Transforms both the current and previous stored transform for an occluder.
+				This allows transforming an occluder without creating a "glitch" in the interpolation.
+				This is particularly useful for large worlds utilising a shifting origin.
+			</description>
+		</method>
+		<method name="canvas_light_reset_physics_interpolation">
+			<return type="void" />
+			<argument index="0" name="light" type="RID" />
+			<description>
+				Prevents physics interpolation for the current physics tick.
+				This is useful when moving a light to a new location, to give an instantaneous change rather than interpolation from the previous location.
+			</description>
+		</method>
 		<method name="canvas_light_set_color">
 			<return type="void" />
 			<argument index="0" name="light" type="RID" />
@@ -557,6 +617,14 @@
 				Sets a canvas light's height.
 			</description>
 		</method>
+		<method name="canvas_light_set_interpolated">
+			<return type="void" />
+			<argument index="0" name="light" type="RID" />
+			<argument index="1" name="interpolated" type="bool" />
+			<description>
+				Turns on and off physics interpolation for the light.
+			</description>
+		</method>
 		<method name="canvas_light_set_item_cull_mask">
 			<return type="void" />
 			<argument index="0" name="light" type="RID" />
@@ -679,6 +747,16 @@
 				Sets the Z range of objects that will be affected by this light. Equivalent to [member Light2D.range_z_min] and [member Light2D.range_z_max].
 			</description>
 		</method>
+		<method name="canvas_light_transform_physics_interpolation">
+			<return type="void" />
+			<argument index="0" name="light" type="RID" />
+			<argument index="1" name="xform" type="Transform2D" />
+			<description>
+				Transforms both the current and previous stored transform for a light.
+				This allows transforming a light without creating a "glitch" in the interpolation.
+				This is particularly useful for large worlds utilising a shifting origin.
+			</description>
+		</method>
 		<method name="canvas_occluder_polygon_create">
 			<return type="RID" />
 			<description>

diff --git a/main/main.cpp b/main/main.cpp
@@ -2324,6 +2324,12 @@ bool Main::iteration() {
 
 		PhysicsServer::get_singleton()->flush_queries();
 
+		// Prepare the fixed timestep interpolated nodes
+		// BEFORE they are updated by the physics 2D,
+		// otherwise the current and previous transforms
+		// may be the same, and no interpolation takes place.
+		OS::get_singleton()->get_main_loop()->iteration_prepare();
+
 		Physics2DServer::get_singleton()->sync();
 		Physics2DServer::get_singleton()->flush_queries();