X-Git-Url: https://git.localhorst.tv/?a=blobdiff_plain;f=src%2Fworld%2FWorld.cpp;h=dcac95eb72708791b37b15f4a29a76035aa0e503;hb=ba1cd7abc93eaacc3c25c0ad1b923b2ce7b280e2;hp=206105ba3d9c3cdf1ffdc5bd943fb3058e9cee99;hpb=3694504331ca888f2cacbcb841a83c402d26934a;p=gworm.git

diff --git a/src/world/World.cpp b/src/world/World.cpp
index 206105b..dcac95e 100644
--- a/src/world/World.cpp
+++ b/src/world/World.cpp
@@ -15,10 +15,105 @@ World::World(Vector<int> size)
 
 
 void World::Update(float dt) {
+	constexpr float fricDyn = 0.75f;
+	constexpr float fricStat = 2.5f;
+	constexpr float dragFact = 0.05f;
+
 	for (Entity &e : entities) {
-		e.acc = ForceAt(e.pos, e.mass) / e.mass;
+		const Vector<float> gravity = ForceAt(e.pos, e.mass);
+		const Vector<float> drag = Rotate180(e.vel) * dragFact;
+		// TODO: drag should be inverse square. and not onmipresent
+
+		e.acc = (gravity + drag) / e.mass;
 		e.Update(dt);
+
+		Vector<float> at;
+		if (WorldCollision(e, at)) {
+			float speed = Length(e.vel);
+			Vector<float> normVel = e.vel / speed;
+			float steps = 0;
+			while (MassAt(e.pos) > 0) {
+				e.pos -= normVel;
+				steps += 1.0f;
+			}
+			const Vector<float> normal = NormalAt(e.pos + normVel);
+			e.vel = Reflect(e.vel, normal);
+			speed = Length(e.vel);
+			normVel = e.vel / speed;
+			// some kind of friction, depends on angle to normal
+			speed *= (fricDyn * (std::abs(Dot(normVel, normal))));
+			if (speed > fricStat) {
+				speed -= fricStat;
+				e.vel = normVel * speed;
+				e.pos += normVel * steps;
+			} else {
+				e.vel = Vector<float>(0, 0);
+			}
+		}
+	}
+}
+
+
+bool World::WorldCollision(const Entity &e, Vector<float> &at) const {
+	if (InBounds(e.pos) && MassAt(e.pos) > 0) {
+		at = e.pos;
+		return true;
+	} else {
+		return false;
+	}
+}
+
+Vector<float> World::NormalAt(Vector<float> pos) const {
+	constexpr Vector<float> check[] = {
+		{  0,        -2        },
+		{  0.765367, -1.84776  },
+		{  1.41421,  -1.41421  },
+		{  1.84776,  -0.765367 },
+		{  2,         0        },
+		{  1.84776,   0.765367 },
+		{  1.41421,   1.41421  },
+		{  0.765367,  1.84776  },
+		{  0,         2        },
+		{ -0.765367,  1.84776  },
+		{ -1.41421,   1.41421  },
+		{ -1.84776,   0.765367 },
+		{ -2,         0        },
+		{ -1.84776,  -0.765367 },
+		{ -1.41421,  -1.41421  },
+		{ -0.765367, -1.84776  },
+	};
+	Vector<float> normal;
+	for (auto v : check) {
+		if (MassAt(pos + v) == 0) {
+			normal += v;
+		}
 	}
+	return Norm(normal);
+}
+
+//Vector<float> World::NormalAt(Vector<float> pos) const {
+//	Vector<int> begin(pos - Vector<float>(3, 3));
+//	Vector<int> end(pos + Vector<float>(3, 3));
+//
+//	Vector<float> normal;
+//	for (Vector<int> cur(begin); cur.y < end.y; ++cur.y) {
+//		for (cur.x = begin.x; cur.x < end.x; ++cur.x) {
+//			if (IsSurface(cur) > 0) {
+//				const Vector<float> dir = pos - Vector<float>(cur);
+//				normal += Rotate90(dir);
+//			}
+//		}
+//	}
+//
+//	return Norm(normal);
+//}
+
+bool World::IsSurface(Vector<int> pos) const {
+	return MassAt(pos) > 0 && (
+			MassAt(pos - Vector<int>(1, 0)) == 0 ||
+			MassAt(pos + Vector<int>(1, 0)) == 0 ||
+			MassAt(pos - Vector<int>(0, 1)) == 0 ||
+			MassAt(pos + Vector<int>(0, 1)) == 0);
 }
 
 
@@ -28,6 +123,8 @@ Entity &World::AddEntity(const Entity &e) {
 }
 
 
+// returns <1.37136364,1.37136734> for 1 mass at <0,0>
+/*
 Vector<float> World::ForceAt(Vector<float> p1, float m1) const {
 	Vector<float> force(0, 0);
 
@@ -48,5 +145,33 @@ Vector<float> World::ForceAt(Vector<float> p1, float m1) const {
 
 	return force;
 }
+*/
+
+// returns <1.37136674,1.37136662> for 1 mass at <0,0>
+// (should be less prone to rounding loss, i.e. more accurate)
+Vector<float> World::ForceAt(Vector<float> p1, float m1) const {
+	Vector<float> force(0, 0);
+
+	for (Vector<int> p2(0, 0); p2.y < size.y; ++p2.y) {
+		Vector<float> rowForce(0, 0);
+		for (p2.x = 0; p2.x < size.x; ++p2.x) {
+			const int i = Index(p2);
+			if (p1 == Vector<float>(p2)) continue;
+
+			const Vector<float> diff(Vector<float>(p2) - p1);
+			const Vector<float> dir(Norm(diff));
+
+			const float m2 = masses[i];
+			const float r2 = Dot(diff, diff);
+
+			const float mag = G * ((m1 * m2) / r2) * 2; // double because m2 is our reference frame
+
+			rowForce += dir * mag;
+		}
+		force += rowForce;
+	}
+
+	return force;
+}
 
 }