render vertices in addition to edges

include/config.hpp

@@ -6,11 +6,12 @@
 constexpr int WIDTH = 800;
 constexpr int HEIGHT = 800;
 
-constexpr float VERTEX_SIZE = 5.0;
+constexpr float VERTEX_SIZE = 50.0;
 constexpr Color VERTEX_COLOR = {27, 188, 104, 255};
 constexpr Color EDGE_COLOR = {20, 133, 38, 255};
 
 constexpr float SIM_SPEED = 4.0;
+constexpr float ROTATION_SPEED = 1.0;
 constexpr float CAMERA_DISTANCE = 2.2;
 
 constexpr float DEFAULT_SPRING_CONSTANT = 1.5;

include/mass_springs.hpp

@@ -115,9 +115,7 @@ public:
 
   auto CalculateSpringForces() -> void;
 
-  auto IntegrateVelocities(const float delta_time) -> void;
-
-  auto IntegratePositions(const float delta_time) -> void;
+  auto EulerUpdate(const float delta_time) -> void;
 
   auto VerletUpdate(const float delta_time) -> void;
 };

include/renderer.hpp

@@ -8,8 +8,11 @@
 
 #include "mass_springs.hpp"
 
-using Edge2Set = std::vector<std::pair<Vector2, Vector2>>;
 using Edge3Set = std::vector<std::pair<Vector3, Vector3>>;
+using Edge2Set = std::vector<std::pair<Vector2, Vector2>>;
+using Vertex2Set =
+    std::vector<Vector3>; // Vertex2Set uses Vector3 to retain the z-coordinate
+                          // for circle size adaptation
 
 class Renderer {
 private:
@@ -40,10 +43,12 @@ private:
   auto Map(const Vector2 &a) -> Vector2;
 
 public:
-  auto Transform(Edge2Set &edges, const MassSpringSystem &mass_springs,
-                 const float angle, const float distance) -> void;
+  auto Transform(Edge2Set &edges, Vertex2Set &vertices,
+                 const MassSpringSystem &mass_springs, const float angle,
+                 const float distance) -> void;
 
-  auto Draw(const Edge2Set &edges) -> void;
+  auto DrawMassSprings(const Edge2Set &edges, const Vertex2Set &vertices)
+      -> void;
 };
 
 #endif

src/main.cpp

@@ -23,9 +23,6 @@ auto main(int argc, char *argv[]) -> int {
 
   InitWindow(WIDTH, HEIGHT, "MassSprings");
 
-  Edge3Set edges;
-  Edge2Set viewport;
-  viewport.reserve(edges.size());
 
   MassSpringSystem mass_springs;
   mass_springs.AddMass(1.0, Vector3(-0.5, 0.5, 0.0), true);
@@ -37,6 +34,10 @@ auto main(int argc, char *argv[]) -> int {
                          DEFAULT_DAMPENING_CONSTANT, DEFAULT_REST_LENGTH);
 
   Renderer renderer(WIDTH, HEIGHT);
+  Edge2Set edges;
+  edges.reserve(mass_springs.springs.size());
+  Vertex2Set vertices;
+  vertices.reserve(mass_springs.masses.size());
 
   float frametime;
   float abstime = 0.0;
@@ -48,28 +49,15 @@ auto main(int argc, char *argv[]) -> int {
 #ifdef VERLET_UPDATE
     mass_springs.VerletUpdate(frametime * SIM_SPEED);
 #else
-    mass_springs.IntegrateVelocities(frametime * SIM_SPEED);
-    mass_springs.IntegratePositions(frametime * SIM_SPEED);
+    mass_springs.EulerUpdate(frametime * SIM_SPEED);
 #endif
 
-    // std::cout << "Calculating Spring Forces: A: (" << massA.force.x << ", "
-    //           << massA.force.y << ", " << massA.force.z << ") B: ("
-    //           << massB.force.x << ", " << massB.force.y << ", " <<
-    //           massB.force.z
-    //           << ")" << std::endl;
-    // std::cout << "Calculating Velocities: A: (" << massA.velocity.x << ", "
-    //           << massA.velocity.y << ", " << massA.velocity.z << ") B: ("
-    //           << massB.velocity.x << ", " << massB.velocity.y << ", "
-    //           << massB.velocity.z << ")" << std::endl;
-    // std::cout << "Calculating Positions: A: (" << massA.position.x << ", "
-    //           << massA.position.y << ", " << massA.position.z << ") B: ("
-    //           << massB.position.x << ", " << massB.position.y << ", "
-    //           << massB.position.z << ")" << std::endl;
+    renderer.Transform(edges, vertices, mass_springs, abstime * ROTATION_SPEED,
+                       CAMERA_DISTANCE);
+    renderer.DrawMassSprings(edges, vertices);
 
-    renderer.Transform(viewport, mass_springs, 0.0, CAMERA_DISTANCE);
     renderer.Draw(viewport);
-
-    abstime += frametime * SIM_SPEED;
+    abstime += frametime;
   }
 
   CloseWindow();

src/mass_springs.cpp

@@ -104,14 +104,9 @@ auto MassSpringSystem::CalculateSpringForces() -> void {
   }
 }
 
-auto MassSpringSystem::IntegrateVelocities(const float delta_time) -> void {
+auto MassSpringSystem::EulerUpdate(const float delta_time) -> void {
   for (auto &mass : masses) {
     mass.CalculateVelocity(delta_time);
-  }
-}
-
-auto MassSpringSystem::IntegratePositions(const float delta_time) -> void {
-  for (auto &mass : masses) {
     mass.CalculatePosition(delta_time);
   }
 }

src/renderer.cpp

@@ -21,31 +21,47 @@ auto Renderer::Map(const Vector2 &a) -> Vector2 {
   return Vector2((1.0 + a.x) / 2.0 * width, (1.0 - a.y) * height / 2.0);
 }
 
-auto Renderer::Transform(Edge2Set &edges, const MassSpringSystem &mass_springs,
+auto Renderer::Transform(Edge2Set &edges, Vertex2Set &vertices,
+                         const MassSpringSystem &mass_springs,
                          const float angle, const float distance) -> void {
-  edges.clear();
-
   const float cos_angle = cos(angle);
   const float sin_angle = sin(angle);
 
+  edges.clear();
   for (const auto &spring : mass_springs.springs) {
-    Vector2 at = Map(Project(Translate(
+    Vector2 a = Map(Project(Translate(
         Rotate(spring.massA.position, cos_angle, sin_angle), distance)));
-    Vector2 bt = Map(Project(Translate(
+    Vector2 b = Map(Project(Translate(
         Rotate(spring.massB.position, cos_angle, sin_angle), distance)));
 
-    edges.emplace_back(at, bt);
+    edges.emplace_back(a, b);
+  }
+
+  // This is duplicated work, but easy to read
+  vertices.clear();
+  for (const auto &mass : mass_springs.masses) {
+    Vector3 a =
+        Translate(Rotate(mass.position, cos_angle, sin_angle), distance);
+    Vector2 b = Map(Project(a));
+
+    vertices.emplace_back(b.x, b.y, a.z);
   }
 }
 
-auto Renderer::Draw(const Edge2Set &edges) -> void {
+auto Renderer::DrawMassSprings(const Edge2Set &edges,
+                               const Vertex2Set &vertices) -> void {
   BeginTextureMode(render_target);
   ClearBackground(RAYWHITE);
   for (const auto &[a, b] : edges) {
     DrawLine(a.x, a.y, b.x, b.y, EDGE_COLOR);
-    DrawCircle(a.x, a.y, VERTEX_SIZE, VERTEX_COLOR);
-    DrawCircle(b.x, b.y, VERTEX_SIZE, VERTEX_COLOR);
   }
+  for (const auto &a : vertices) {
+    // Increase the perspective perception by squaring the z-coordinate
+    const float size = VERTEX_SIZE / (a.z * a.z);
+
+    DrawRectangle(a.x - size / 2.0, a.y - size / 2.0, size, size, VERTEX_COLOR);
+  }
+  DrawLine(0, 0, 0, height, BLACK);
   EndTextureMode();
 
   BeginDrawing();