Also interpolate taxi and interactive objects

CHARACTER_INTERPOLATION.md

@@ -44,6 +44,15 @@ Dialogue typewriter text and cutscene presentation timers use the same
 per-render-frame path. This keeps character reveals, subtitle timing, fades, and
 cutscene image poses smooth instead of stepping in 100 ms increments.
 
+Interactive objects retain authoritative move, rotate, scale, and fade tasks on
+the simulation tick. Their previous and current visual transforms are sampled
+at tick boundaries and interpolated only while drawing, so doors and similar
+objects remain logically deterministic while their presentation is smooth.
+
+The same render-only sampling is used for `NpcCar` taxi visuals. Its position,
+body rotation, wheel rotation, and steering angle are interpolated for drawing;
+the authoritative taxi movement and waypoint logic remain fixed-step.
+
 ## Animation skinning
 
 GPU and CPU bone interpolation receive the fractional render frame instead of an

src/Location.cpp

@@ -1134,12 +1134,8 @@ namespace FRG
 		drawInstancedStatics("shadow_depth_inst", InstancedTexture::None);
 
 		for (auto& intObj : interactiveObjects) {
-			if (intObj.state.castShadow && intObj.loadedObject.texture) {
+			if (intObj.state.castShadow)
-				renderer.PushMatrix();
+				intObj.drawShadowDepth(renderer);
-				renderer.TranslateMatrix(intObj.state.position);
-				renderer.DrawVertexRenderStruct(intObj.loadedObject.mesh);
-				renderer.PopMatrix();
-			}
 		}
 
 		// Draw characters (they handle their own skinning shader switch internally)
@@ -1431,12 +1427,8 @@ namespace FRG
 		}
 		drawInstancedStatics("shadow_depth_inst", InstancedTexture::None);
 		for (auto& intObj : interactiveObjects) {
-			if (intObj.state.castShadowNight && intObj.loadedObject.texture) {
+			if (intObj.state.castShadowNight)
-				renderer.PushMatrix();
+				intObj.drawShadowDepth(renderer);
-				renderer.TranslateMatrix(intObj.state.position);
-				renderer.DrawVertexRenderStruct(intObj.loadedObject.mesh);
-				renderer.PopMatrix();
-			}
 		}
 		if (player) player->drawShadowDepth(renderer);
 		for (auto& [id, remote] : remotePlayers_)
@@ -1453,14 +1445,75 @@ namespace FRG
 		shadowMap->unbind();
 	}
 
+	void Location::captureNpcCarPresentation(const NpcCar& car)
+	{
+		NpcCarPresentationSample sample;
+		sample.position = car.position;
+		sample.rotation = car.rotation;
+		sample.wheelAngle = car.wheelAngle;
+		sample.steeringAngle = car.steeringAngle;
+
+		const auto now = std::chrono::steady_clock::now();
+		const bool largeGap = hasNpcCarPresentationSample_ &&
+			std::chrono::duration_cast<std::chrono::milliseconds>(
+				now - lastNpcCarPresentationUpdate_).count() > 250;
+		if (!hasNpcCarPresentationSample_ || largeGap) {
+			previousNpcCarPresentation_ = sample;
+		} else {
+			previousNpcCarPresentation_ = currentNpcCarPresentation_;
+		}
+		currentNpcCarPresentation_ = sample;
+		lastNpcCarPresentationUpdate_ = now;
+		hasNpcCarPresentationSample_ = true;
+	}
+
+	Location::NpcCarPresentationSample
+	Location::interpolatedNpcCarPresentation(const NpcCar& car) const
+	{
+		NpcCarPresentationSample result;
+		result.position = car.position;
+		result.rotation = car.rotation;
+		result.wheelAngle = car.wheelAngle;
+		result.steeringAngle = car.steeringAngle;
+		if (!hasNpcCarPresentationSample_) return result;
+
+		constexpr float kSimulationTickMs = 100.0f;
+		const float elapsedMs = static_cast<float>(
+			std::chrono::duration_cast<std::chrono::milliseconds>(
+				std::chrono::steady_clock::now() - lastNpcCarPresentationUpdate_).count());
+		const float alpha = (std::max)(0.0f,
+			(std::min)(1.0f, elapsedMs / kSimulationTickMs));
+
+		result.position = previousNpcCarPresentation_.position +
+			alpha * (currentNpcCarPresentation_.position -
+				previousNpcCarPresentation_.position);
+		result.wheelAngle = previousNpcCarPresentation_.wheelAngle +
+			alpha * (currentNpcCarPresentation_.wheelAngle -
+				previousNpcCarPresentation_.wheelAngle);
+		result.steeringAngle = previousNpcCarPresentation_.steeringAngle +
+			alpha * (currentNpcCarPresentation_.steeringAngle -
+				previousNpcCarPresentation_.steeringAngle);
+
+		constexpr float kPi = 3.14159265358979323846f;
+		constexpr float kTwoPi = 2.0f * kPi;
+		float rotationDelta = currentNpcCarPresentation_.rotation -
+			previousNpcCarPresentation_.rotation;
+		while (rotationDelta > kPi) rotationDelta -= kTwoPi;
+		while (rotationDelta < -kPi) rotationDelta += kTwoPi;
+		result.rotation = previousNpcCarPresentation_.rotation + alpha * rotationDelta;
+		return result;
+	}
+
 	void Location::drawNpcCar()
 	{
 		auto locationState = stateSnapshot();
 		if (!locationState) return;
+		const NpcCarPresentationSample car =
+			interpolatedNpcCarPresentation(locationState->taxiCar);
 		renderer.PushMatrix();
-		renderer.TranslateMatrix(locationState->taxiCar.position);
+		renderer.TranslateMatrix(car.position);
 		renderer.TranslateMatrix({ 0, 0.7f - 0.25f +x, 0 });
-		renderer.RotateMatrix(Eigen::Quaternionf(Eigen::AngleAxisf(locationState->taxiCar.rotation, Eigen::Vector3f::UnitY())).toRotationMatrix());
+		renderer.RotateMatrix(Eigen::Quaternionf(Eigen::AngleAxisf(car.rotation, Eigen::Vector3f::UnitY())).toRotationMatrix());
 		glBindTexture(GL_TEXTURE_2D, carTexture->getTexID());
 		renderer.DrawVertexRenderStruct(carMesh);
 
@@ -1480,10 +1533,10 @@ namespace FRG
 			for (int i = 0; i < 4; ++i) {
 				renderer.PushMatrix();
 				renderer.TranslateMatrix(wheelPositions[i]);
-				renderer.RotateMatrix(Eigen::Quaternionf(Eigen::AngleAxisf(locationState->taxiCar.wheelAngle, -Eigen::Vector3f::UnitX())).toRotationMatrix());
+				renderer.RotateMatrix(Eigen::Quaternionf(Eigen::AngleAxisf(car.wheelAngle, -Eigen::Vector3f::UnitX())).toRotationMatrix());
 
 				if (isFront[i]) {
-					renderer.RotateMatrix(Eigen::Quaternionf(Eigen::AngleAxisf(locationState->taxiCar.steeringAngle, Eigen::Vector3f::UnitY())).toRotationMatrix());
+					renderer.RotateMatrix(Eigen::Quaternionf(Eigen::AngleAxisf(car.steeringAngle, Eigen::Vector3f::UnitY())).toRotationMatrix());
 				}
 				renderer.DrawVertexRenderStruct(carWheelMesh);
 				renderer.PopMatrix();
@@ -1800,6 +1853,7 @@ namespace FRG
 		if (!locationState) return;
 		auto gameSnapshot = gameServer_.snapshot();
 		if (!gameSnapshot) return;
+		captureNpcCarPresentation(locationState->taxiCar);
 		if (events.taxiArrived)
 			scriptEngine.callCallTaxiCallback();
 
@@ -1936,6 +1990,8 @@ namespace FRG
 			}
 		}
 
+		for (auto& intObj : interactiveObjects)
+			intObj.capturePresentationState();
 	}
 
 	void Location::handleDown(int64_t fingerId, int eventX, int eventY, int mx, int my)

src/Location.h

@@ -19,6 +19,7 @@
 #include "LocationGameState.h"
 #include <functional>
 #include <cstdint>
+#include <chrono>
 #include <unordered_map>
 #include "Character.h"
 
@@ -265,6 +266,21 @@ namespace FRG
 
 		PathVisualization pathVisualization;
 
+		struct NpcCarPresentationSample {
+			Eigen::Vector3f position = Eigen::Vector3f::Zero();
+			float rotation = 0.f;
+			float wheelAngle = 0.f;
+			float steeringAngle = 0.f;
+		};
+
+		NpcCarPresentationSample previousNpcCarPresentation_;
+		NpcCarPresentationSample currentNpcCarPresentation_;
+		std::chrono::steady_clock::time_point lastNpcCarPresentationUpdate_;
+		bool hasNpcCarPresentationSample_ = false;
+
+		void captureNpcCarPresentation(const NpcCar& car);
+		NpcCarPresentationSample interpolatedNpcCarPresentation(const NpcCar& car) const;
+
 	};
 
 } // namespace FRG

src/items/InteractiveObject.cpp

@@ -5,6 +5,8 @@
 #include <iostream>
 #include <string>
 #include <algorithm>
+#include <chrono>
+#include <cmath>
 #include <Eigen/Geometry>
 
 namespace FRG {
@@ -68,8 +70,72 @@ namespace FRG {
     }
 
 
+    void InteractiveObject::capturePresentationState()
+    {
+        PresentationSample sample;
+        sample.position = state.position;
+        sample.rotationY = state.rotationY;
+        sample.scale = state.scale;
+        sample.alpha = state.alpha;
+        sample.isActive = state.isActive;
+
+        const auto now = std::chrono::steady_clock::now();
+        const bool largeGap = hasPresentationSample_ &&
+            std::chrono::duration_cast<std::chrono::milliseconds>(
+                now - lastPresentationUpdate_).count() > 250;
+        if (!hasPresentationSample_ || largeGap ||
+            currentPresentationSample_.isActive != sample.isActive) {
+            previousPresentationSample_ = sample;
+        } else {
+            previousPresentationSample_ = currentPresentationSample_;
+        }
+        currentPresentationSample_ = sample;
+        lastPresentationUpdate_ = now;
+        hasPresentationSample_ = true;
+    }
+
+    InteractiveObject::PresentationSample
+    InteractiveObject::interpolatedPresentationState() const
+    {
+        PresentationSample result;
+        result.position = state.position;
+        result.rotationY = state.rotationY;
+        result.scale = state.scale;
+        result.alpha = state.alpha;
+        result.isActive = state.isActive;
+        if (!hasPresentationSample_) return result;
+
+        constexpr float kSimulationTickMs = 100.0f;
+        const float elapsedMs = static_cast<float>(
+            std::chrono::duration_cast<std::chrono::milliseconds>(
+                std::chrono::steady_clock::now() - lastPresentationUpdate_).count());
+        const float alpha = (std::max)(0.0f,
+            (std::min)(1.0f, elapsedMs / kSimulationTickMs));
+
+        result.position = previousPresentationSample_.position +
+            alpha * (currentPresentationSample_.position -
+                     previousPresentationSample_.position);
+        result.scale = previousPresentationSample_.scale +
+            alpha * (currentPresentationSample_.scale -
+                     previousPresentationSample_.scale);
+        result.alpha = previousPresentationSample_.alpha +
+            alpha * (currentPresentationSample_.alpha -
+                     previousPresentationSample_.alpha);
+
+        constexpr float kPi = 3.14159265358979323846f;
+        constexpr float kTwoPi = 2.0f * kPi;
+        float rotationDelta = currentPresentationSample_.rotationY -
+            previousPresentationSample_.rotationY;
+        while (rotationDelta > kPi) rotationDelta -= kTwoPi;
+        while (rotationDelta < -kPi) rotationDelta += kTwoPi;
+        result.rotationY = previousPresentationSample_.rotationY +
+            alpha * rotationDelta;
+        return result;
+    }
+
     void InteractiveObject::drawDarklands(Renderer& renderer) const {
         if (!state.isActive || !loadedObject.textureDarklands) return;
+        const PresentationSample presentation = interpolatedPresentationState();
 
         if (state.alpha < 0.999f) {
             glEnable(GL_BLEND);
@@ -77,16 +143,16 @@ namespace FRG {
         }
 
         renderer.PushMatrix();
-        renderer.TranslateMatrix(state.position);
+        renderer.TranslateMatrix(presentation.position);
-        if (state.rotationY != 0.f) {
+        if (presentation.rotationY != 0.f) {
             renderer.TranslateMatrix(state.pivot);
-            renderer.RotateMatrix(Eigen::AngleAxisf(state.rotationY, Eigen::Vector3f::UnitY()).toRotationMatrix());
+            renderer.RotateMatrix(Eigen::AngleAxisf(presentation.rotationY, Eigen::Vector3f::UnitY()).toRotationMatrix());
             renderer.TranslateMatrix(-state.pivot);
         }
-        if (state.scale != 1.f)
+        if (presentation.scale != 1.f)
-            renderer.ScaleMatrix(state.scale);
+            renderer.ScaleMatrix(presentation.scale);
         renderer.RenderUniform1i(textureUniformName, 0);
-        renderer.RenderUniform1f("uAlpha", state.alpha);
+        renderer.RenderUniform1f("uAlpha", presentation.alpha);
         glBindTexture(GL_TEXTURE_2D, loadedObject.textureDarklands->getTexID());
         renderer.DrawVertexRenderStruct(loadedObject.mesh);
         renderer.PopMatrix();
@@ -96,6 +162,7 @@ namespace FRG {
 
     void InteractiveObject::draw(Renderer& renderer) const {
         if (!state.isActive || !loadedObject.texture) return;
+        const PresentationSample presentation = interpolatedPresentationState();
 
         if (state.alpha < 0.999f) {
             glEnable(GL_BLEND);
@@ -103,16 +170,16 @@ namespace FRG {
         }
 
         renderer.PushMatrix();
-        renderer.TranslateMatrix(state.position);
+        renderer.TranslateMatrix(presentation.position);
-        if (state.rotationY != 0.f) {
+        if (presentation.rotationY != 0.f) {
             renderer.TranslateMatrix(state.pivot);
-            renderer.RotateMatrix(Eigen::AngleAxisf(state.rotationY, Eigen::Vector3f::UnitY()).toRotationMatrix());
+            renderer.RotateMatrix(Eigen::AngleAxisf(presentation.rotationY, Eigen::Vector3f::UnitY()).toRotationMatrix());
             renderer.TranslateMatrix(-state.pivot);
         }
-        if (state.scale != 1.f)
+        if (presentation.scale != 1.f)
-            renderer.ScaleMatrix(state.scale);
+            renderer.ScaleMatrix(presentation.scale);
         renderer.RenderUniform1i(textureUniformName, 0);
-        renderer.RenderUniform1f("uAlpha", state.alpha);
+        renderer.RenderUniform1f("uAlpha", presentation.alpha);
         glBindTexture(GL_TEXTURE_2D, loadedObject.texture->getTexID());
         renderer.DrawVertexRenderStruct(loadedObject.mesh);
         renderer.PopMatrix();
@@ -120,4 +187,23 @@ namespace FRG {
         renderer.RenderUniform1f("uAlpha", 1.0f);
     }
 
+    void InteractiveObject::drawShadowDepth(Renderer& renderer) const
+    {
+        if (!state.isActive) return;
+        const PresentationSample presentation = interpolatedPresentationState();
+
+        renderer.PushMatrix();
+        renderer.TranslateMatrix(presentation.position);
+        if (presentation.rotationY != 0.f) {
+            renderer.TranslateMatrix(state.pivot);
+            renderer.RotateMatrix(Eigen::AngleAxisf(
+                presentation.rotationY, Eigen::Vector3f::UnitY()).toRotationMatrix());
+            renderer.TranslateMatrix(-state.pivot);
+        }
+        if (presentation.scale != 1.f)
+            renderer.ScaleMatrix(presentation.scale);
+        renderer.DrawVertexRenderStruct(loadedObject.mesh);
+        renderer.PopMatrix();
+    }
+
 } // namespace FRG

src/items/InteractiveObject.h

@@ -4,6 +4,7 @@
 #include <Eigen/Core>
 #include "render/Renderer.h"
 #include "InteractiveObjectState.h"
+#include <chrono>
 
 namespace FRG {
 
@@ -30,6 +31,8 @@ namespace FRG {
 
 		void draw(Renderer& renderer) const;
 		void drawDarklands(Renderer& renderer) const;
+		void drawShadowDepth(Renderer& renderer) const;
+		void capturePresentationState();
 		const std::string& entityId() const { return id; }
 
 	private:
@@ -38,6 +41,21 @@ namespace FRG {
 		friend class LocationEditor;
 		friend class ScriptEngine;
 		InteractiveObjectState& state; // non-owning binding to LocationGameState
+
+		struct PresentationSample {
+			Eigen::Vector3f position = Eigen::Vector3f::Zero();
+			float rotationY = 0.f;
+			float scale = 1.f;
+			float alpha = 1.f;
+			bool isActive = true;
+		};
+
+		PresentationSample previousPresentationSample_;
+		PresentationSample currentPresentationSample_;
+		std::chrono::steady_clock::time_point lastPresentationUpdate_;
+		bool hasPresentationSample_ = false;
+
+		PresentationSample interpolatedPresentationState() const;
 	};
 
 } // namespace FRG