From: Daniel Karbach <daniel.karbach@localhorst.tv>
Date: Mon, 27 Nov 2017 21:05:20 +0000 (+0100)
Subject: use RK4 to integrate creature state
X-Git-Url: https://git.localhorst.tv/?a=commitdiff_plain;h=b0e73e632f0b681a0af78f889dd82d370563944a;p=blobs.git

use RK4 to integrate creature state
---

diff --git a/src/creature/Creature.hpp b/src/creature/Creature.hpp
index 7c06cc8..e2f9b44 100644
--- a/src/creature/Creature.hpp
+++ b/src/creature/Creature.hpp
@@ -94,15 +94,14 @@ public:
 	Steering &GetSteering() noexcept { return steering; }
 	const Steering &GetSteering() const noexcept { return steering; }
 
-	void Velocity(const glm::dvec3 &v) noexcept { vel = v; }
-	const glm::dvec3 &Velocity() const noexcept { return vel; }
-	bool Moving() const noexcept { return glm::length2(vel) < 0.00000001; }
-
 	glm::dmat4 LocalTransform() noexcept;
 
 	void BuildVAO();
 	void Draw(graphics::Viewport &);
 
+private:
+	Situation::Derivative Step(const Situation::Derivative &ds, double dt) const noexcept;
+
 private:
 	world::Simulation &sim;
 	std::string name;
@@ -127,8 +126,6 @@ private:
 	Situation situation;
 	Steering steering;
 
-	glm::dvec3 vel;
-
 	struct Attributes {
 		glm::vec3 position;
 		glm::vec3 normal;
diff --git a/src/creature/Situation.hpp b/src/creature/Situation.hpp
index a60aeb7..a12f422 100644
--- a/src/creature/Situation.hpp
+++ b/src/creature/Situation.hpp
@@ -14,6 +14,24 @@ namespace creature {
 
 class Situation {
 
+public:
+	struct State {
+		glm::dvec3 pos;
+		glm::dvec3 vel;
+		State(
+			const glm::dvec3 &pos = glm::dvec3(0.0),
+			const glm::dvec3 &vel = glm::dvec3(0.0))
+		: pos(pos), vel(vel) { }
+	};
+	struct Derivative {
+		glm::dvec3 vel;
+		glm::dvec3 acc;
+		Derivative(
+			const glm::dvec3 &vel = glm::dvec3(0.0),
+			const glm::dvec3 &acc = glm::dvec3(0.0))
+		: vel(vel), acc(acc) { }
+	};
+
 public:
 	Situation();
 	~Situation();
@@ -29,18 +47,22 @@ public:
 	world::Planet &GetPlanet() const noexcept { return *planet; }
 	bool OnSurface() const noexcept;
 	int Surface() const noexcept { return surface; }
-	const glm::dvec3 &Position() const noexcept { return position; }
+	const glm::dvec3 &Position() const noexcept { return state.pos; }
 	bool OnTile() const noexcept;
 	glm::ivec2 SurfacePosition() const noexcept;
 	world::Tile &GetTile() const noexcept;
 	const world::TileType &GetTileType() const noexcept;
 
+	void SetState(const State &s) noexcept { state = s; }
+	const State &GetState() const noexcept { return state; }
+
+	bool Moving() const noexcept { return glm::length2(state.vel) < 0.00000001; }
 	void Move(const glm::dvec3 &dp) noexcept;
 	void SetPlanetSurface(world::Planet &, int srf, const glm::dvec3 &pos) noexcept;
 
 public:
 	world::Planet *planet;
-	glm::dvec3 position;
+	State state;
 	int surface;
 	enum {
 		LOST,
diff --git a/src/creature/Steering.hpp b/src/creature/Steering.hpp
index 51f2c63..3ccf9e3 100644
--- a/src/creature/Steering.hpp
+++ b/src/creature/Steering.hpp
@@ -1,14 +1,13 @@
 #ifndef BLOBS_CREATURE_STEERING_HPP_
 #define BLOBS_CREATURE_STEERING_HPP_
 
+#include "Situation.hpp"
 #include "../math/glm.hpp"
 
 
 namespace blobs {
 namespace creature {
 
-class Creature;
-
 class Steering {
 
 public:
@@ -26,7 +25,7 @@ public:
 	void Halt() noexcept;
 	void GoTo(const glm::dvec3 &) noexcept;
 
-	glm::dvec3 Acceleration(Creature &) const noexcept;
+	glm::dvec3 Acceleration(const Situation::State &) const noexcept;
 
 private:
 	bool SumForce(glm::dvec3 &out, const glm::dvec3 &in) const noexcept;
diff --git a/src/creature/creature.cpp b/src/creature/creature.cpp
index f51f52c..d870755 100644
--- a/src/creature/creature.cpp
+++ b/src/creature/creature.cpp
@@ -43,7 +43,6 @@ Creature::Creature(world::Simulation &sim)
 , goals()
 , situation()
 , steering()
-, vel(0.0)
 , vao() {
 }
 
@@ -106,10 +105,20 @@ bool GoalCompare(const std::unique_ptr<Goal> &a, const std::unique_ptr<Goal> &b)
 }
 
 void Creature::Tick(double dt) {
-	// TODO: better integration method
-	glm::dvec3 acc(steering.Acceleration(*this));
-	situation.Move(vel * dt);
-	vel += acc * dt;
+	{
+		Situation::State state(situation.GetState());
+		Situation::Derivative a(Step(Situation::Derivative(), 0.0));
+		Situation::Derivative b(Step(a, dt * 0.5));
+		Situation::Derivative c(Step(b, dt * 0.5));
+		Situation::Derivative d(Step(c, dt));
+		Situation::Derivative f(
+			(1.0 / 6.0) * (a.vel + 2.0 * (b.vel + c.vel) + d.vel),
+			(1.0 / 6.0) * (a.acc + 2.0 * (b.acc + c.acc) + d.acc)
+		);
+		state.pos += f.vel * dt;
+		state.vel += f.acc * dt;
+		situation.SetState(state);
+	}
 
 	if (Age() > properties.death_age) {
 		std::cout << "[" << int(sim.Time()) << "s] "
@@ -153,6 +162,13 @@ void Creature::Tick(double dt) {
 	}
 }
 
+Situation::Derivative Creature::Step(const Situation::Derivative &ds, double dt) const noexcept {
+	Situation::State s = situation.GetState();
+	s.pos += ds.vel * dt;
+	s.vel += ds.acc * dt;
+	return { s.vel, steering.Acceleration(s) };
+}
+
 glm::dmat4 Creature::LocalTransform() noexcept {
 	// TODO: surface transform
 	const double half_size = size * 0.5;
@@ -445,7 +461,7 @@ std::string NameGenerator::Sequential() {
 
 Situation::Situation()
 : planet(nullptr)
-, position(0.0)
+, state(glm::dvec3(0.0), glm::dvec3(0.0))
 , surface(0)
 , type(LOST) {
 }
@@ -462,34 +478,34 @@ bool Situation::OnSurface() const noexcept {
 }
 
 bool Situation::OnTile() const noexcept {
-	glm::ivec2 t(planet->SurfacePosition(surface, position));
+	glm::ivec2 t(planet->SurfacePosition(surface, state.pos));
 	return type == PLANET_SURFACE
 		&& t.x >= 0 && t.x < planet->SideLength()
 		&& t.y >= 0 && t.y < planet->SideLength();
 }
 
 glm::ivec2 Situation::SurfacePosition() const noexcept {
-	return planet->SurfacePosition(surface, position);
+	return planet->SurfacePosition(surface, state.pos);
 }
 
 world::Tile &Situation::GetTile() const noexcept {
-	glm::ivec2 t(planet->SurfacePosition(surface, position));
+	glm::ivec2 t(planet->SurfacePosition(surface, state.pos));
 	return planet->TileAt(surface, t.x, t.y);
 }
 
 const world::TileType &Situation::GetTileType() const noexcept {
-	glm::ivec2 t(planet->SurfacePosition(surface, position));
+	glm::ivec2 t(planet->SurfacePosition(surface, state.pos));
 	return planet->TypeAt(surface, t.x, t.y);
 }
 
 void Situation::Move(const glm::dvec3 &dp) noexcept {
-	position += dp;
+	state.pos += dp;
 	if (OnSurface()) {
 		// enforce ground constraint
 		if (Surface() < 3) {
-			position[(Surface() + 2) % 3] = std::max(0.0, position[(Surface() + 2) % 3]);
+			state.pos[(Surface() + 2) % 3] = std::max(0.0, state.pos[(Surface() + 2) % 3]);
 		} else {
-			position[(Surface() + 2) % 3] = std::min(0.0, position[(Surface() + 2) % 3]);
+			state.pos[(Surface() + 2) % 3] = std::min(0.0, state.pos[(Surface() + 2) % 3]);
 		}
 	}
 }
@@ -498,7 +514,7 @@ void Situation::SetPlanetSurface(world::Planet &p, int srf, const glm::dvec3 &po
 	type = PLANET_SURFACE;
 	planet = &p;
 	surface = srf;
-	position = pos;
+	state.pos = pos;
 }
 
 
@@ -524,15 +540,15 @@ void Steering::GoTo(const glm::dvec3 &t) noexcept {
 	seeking = true;
 }
 
-glm::dvec3 Steering::Acceleration(Creature &c) const noexcept {
+glm::dvec3 Steering::Acceleration(const Situation::State &s) const noexcept {
 	glm::dvec3 acc(0.0);
 	if (halting) {
-		SumForce(acc, c.Velocity() * -max_accel);
+		SumForce(acc, s.vel * -max_accel);
 	}
 	if (seeking) {
-		glm::dvec3 diff = seek_target - c.GetSituation().Position();
+		glm::dvec3 diff = seek_target - s.pos;
 		if (!allzero(diff)) {
-			SumForce(acc, ((normalize(diff) * max_speed) - c.Velocity()) * max_accel);
+			SumForce(acc, ((normalize(diff) * max_speed) - s.vel) * max_accel);
 		}
 	}
 	return acc;
diff --git a/src/creature/goal.cpp b/src/creature/goal.cpp
index 8f8a3fa..ee51a91 100644
--- a/src/creature/goal.cpp
+++ b/src/creature/goal.cpp
@@ -138,7 +138,7 @@ void LocateResourceGoal::Action() {
 		}
 	} else if (OnTargetTile()) {
 		GetSteering().Halt();
-		if (!GetCreature().Moving()) {
+		if (!GetSituation().Moving()) {
 			SetComplete();
 		}
 	} else {