some lousy world collision, friction, and drag

diff --git a/src/app/Application.cpp b/src/app/Application.cpp
index d798b37c757f89b75aab6b41a524ed727caaa076..b7983aa0fcc56323e9bc07629cdcf53409c249c5 100644 (file)
--- a/src/app/Application.cpp
+++ b/src/app/Application.cpp
@@ -220,6 +220,7 @@ void Application::RenderUI() {
                canvas.Arrow(screenPos, screenPos + Vector<int>(e.vel * 10.0f));
 
                cout << "entity: pos " << e.pos << ", vel " << e.vel << ", acc " << e.acc << endl;
+               cout << "        vel mag: " << Length(e.vel) << ", acc mag: " << Length(e.acc) << endl;
        }
 }
 

diff --git a/src/graphics/Vector.h b/src/graphics/Vector.h
index d35cf33fcb119be8fb67351c9a3ac6d89951fe80..6565cc116b0f0545cf480a2002b8468a17d77da3 100644 (file)
--- a/src/graphics/Vector.h
+++ b/src/graphics/Vector.h
@@ -3,6 +3,7 @@
 
 #include <algorithm>
 #include <cmath>
+#include <limits>
 #include <ostream>
 #include <SDL.h>
 
@@ -36,6 +37,16 @@ public:
                y -= other.y;
                return *this;
        }
+       Vector<Scalar> &operator *=(Scalar factor) {
+               x *= factor;
+               y *= factor;
+               return *this;
+       }
+       Vector<Scalar> &operator /=(Scalar factor) {
+               x /= factor;
+               y /= factor;
+               return *this;
+       }
 
        SDL_Point ToPoint() const {
                SDL_Point p;
@@ -142,6 +153,13 @@ constexpr bool operator !=(Vector<Scalar> lhs, Vector<Scalar> rhs) {
 }
 
 
+template<class Scalar>
+constexpr bool IsZero(Vector<Scalar> v) {
+       return std::abs(v.x) < std::numeric_limits<Scalar>::epsilon()
+               && std::abs(v.y) < std::numeric_limits<Scalar>::epsilon();
+}
+
+
 template<class Scalar>
 constexpr Scalar Cross2D(Vector<Scalar> lhs, Vector<Scalar> rhs) {
        return (lhs.x * rhs.y) - (lhs.y * rhs.x);
@@ -171,6 +189,19 @@ template<class Scalar>
 constexpr Vector<Scalar> Rotate270(Vector<Scalar> v) {
        return Vector<Scalar>(v.y, -v.x);
 }
+template<class Scalar, class Float>
+inline Vector<Scalar> Rotate(Vector<Scalar> v, Float by) {
+       Float sine(std::sin(by));
+       Float cosine(std::cos(by));
+       return Vector<Scalar>(v.x * cosine - v.y * sine, v.x * sine + v.y * cosine);
+}
+
+/// reflect v along normalized n
+template<class Scalar>
+inline Vector<Scalar> Reflect(Vector<Scalar> v, Vector<Scalar> n) {
+       const Scalar dd = Scalar(2) * Dot(v, n);
+       return Vector<Scalar>(v.x - (dd * n.x), v.y - (dd * n.y));
+}
 
 
 template<class Scalar>

diff --git a/src/gworm.cpp b/src/gworm.cpp
index efd5757324b36bcd89b8d71fe12ba6c21038f707..3f22adea95abfe73638eae6490bffcc8ca6b55c3 100644 (file)
--- a/src/gworm.cpp
+++ b/src/gworm.cpp
@@ -1,11 +1,15 @@
 #include "app/Application.h"
 #include "app/SDL.h"
+#include "graphics/const.h"
 #include "graphics/Canvas.h"
 #include "graphics/Window.h"
 #include "world/Entity.h"
 #include "world/World.h"
 
+#include <iostream>
+
 using namespace gworm;
+using namespace std;
 
 
 namespace {
@@ -48,10 +52,19 @@ int main(int argc, const char *argv[]) {
        World world(Vector<int>(500, 500));
        make_planet(world, Vector<int>(250, 250), 220);
 
-       Entity e;
-       e.vel = Vector<float>(-19, 19);
-       e.mass = 1;
-       world.AddEntity(e);
+       Entity orb;
+       orb.vel = Vector<float>(-19, 19);
+       orb.mass = 1;
+       world.AddEntity(orb);
+
+       Entity coll;
+       coll.pos = Vector<float>(250, -25);
+       coll.vel = Vector<float>(-10, 0);
+       coll.mass = 2;
+       world.AddEntity(coll);
+
+       cout << "normal at top: " << world.NormalAt(Vector<float>(250, 30)) << endl;
+       cout << "normal at left: " << world.NormalAt(Vector<float>(30, 250)) << endl;
 
        Application app(canv, world);
        app.Run();

diff --git a/src/world/World.cpp b/src/world/World.cpp
index 53115dc386360b73558a07ae5ee00bafe381c9e2..dcac95eb72708791b37b15f4a29a76035aa0e503 100644 (file)
--- a/src/world/World.cpp
+++ b/src/world/World.cpp
@@ -15,12 +15,107 @@ 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);
+}
+
 
 Entity &World::AddEntity(const Entity &e) {
        entities.emplace_back(e);

diff --git a/src/world/World.h b/src/world/World.h
index f15d43b8ae818c0a9a6cacf51baa230b48866763..8a00f60541302a489d8e34565c916eecea3f7b5d 100644 (file)
--- a/src/world/World.h
+++ b/src/world/World.h
@@ -22,6 +22,8 @@ public:
 public:
        void Update(float dt);
 
+       bool InBounds(Vector<int> pos) const
+               { return pos.x > 0 && pos.y > 0 && pos.x < size.x && pos.y < size.y; }
        int Index(Vector<int> pos) const { return pos.x * size.y + pos.y; }
 
        float MassAt(Vector<int> pos) const { return masses[Index(pos)]; }
@@ -33,6 +35,9 @@ public:
        Entity &AddEntity(const Entity &);
 
        Vector<float> ForceAt(Vector<float>, float m) const;
+       bool WorldCollision(const Entity &, Vector<float> &) const;
+       Vector<float> NormalAt(Vector<float>) const;
+       bool IsSurface(Vector<int>) const;
 
 private:
        Vector<int> size;