Finish basic spline movement

The speed isn't chosen correctly yet, but the basic movement along the spline is functional!

There are opportunities for a performance increase: Some calculations which we currently do every frame, are actually only necessary once we choose a new point for moving towards.

ECS/Components/PathMove.h

@@ -6,16 +6,18 @@
 
 struct PathMove {
     struct Path {
+        Path(std::vector<glm::vec3> points) : points(points) {}
+        
         std::vector<glm::vec3> points;
     };
 
-    PathMove(double speed) : speed(speed) {}
+    PathMove(double speed, Path path) : speed(speed), path(path) {}
 
     double speed;
 
     Path path;
 
-    int current_point_index;
+    int current_point_index = 0;
 
     float time_passed = 0.0;
 };

ECS/Systems/PathMoveSystem.h

@@ -75,24 +75,70 @@ class PathMoveSystem : public EntitySystem, public EventSubscriber<InputEvent> {
     }
 
     void tick(World *pWorld, float deltaTime) override {
-        PathMove::Path path;
-
-        path.points = std::vector<glm::vec3>{
-            glm::vec3(0.0, 2.0, 0.0),
-            glm::vec3(0.0, 2.0, 1.0),
-            glm::vec3(2.0, 2.0, 2.0),
-            glm::vec3(1.0, 3.0, 3.0),
-            glm::vec3(-2.0, 2.0, 4.0),
-            glm::vec3(2.0, 2.0, 4.0),
-        };
-
         pWorld->each<Transform, PathMove>(
                 [&](Entity *ent, ComponentHandle<Transform> transform, ComponentHandle<PathMove> pathmove) {
+                    // Shorthand for the path (we'll use this a lot)
+                    PathMove::Path path = pathmove->path;
+
+                    // Add the passed time
                     pathmove->time_passed += deltaTime;
 
-                    // Move from the second to the third point for now
+                    // Shorthand for number of points in the path
-                    glm::vec3 point = catmul(0.5f, path.points[0], path.points[1], path.points[2], path.points[3], pathmove->time_passed * 0.5);
+                    int num_points = path.points.size();
+
+                    if (pathmove->time_passed >= 1.0) {
+                        // If we passed the last target, set the current_point_index to that target
+                        pathmove->time_passed -= 1.0;
+                        pathmove->current_point_index += 1;
+
+                        // If the point index is greater than the second to last one, reset
+                        // (The point index specifies the point we're coming from, not the one we're moving towards)
+                        if (pathmove->current_point_index >= num_points - 1) {
+                            pathmove->current_point_index = 0;
+                        }
+                    }
+
+                    // The four points which are needed for the spline
+                    // p1 and p2 are always the same (the current origin and the current target), but the rest depends on edge cases
+                    glm::vec3 p0;
+                    glm::vec3 p1 = path.points[pathmove->current_point_index];
+                    glm::vec3 p2 = path.points[pathmove->current_point_index + 1];
+                    glm::vec3 p3;
+
+                    if (pathmove->current_point_index == num_points - 2) {
+                        // We're moving towards the last point, so the point after that needs to be interpolated.
+                        // We interpolate linearly along the line from this point to the target point.
+                        glm::vec3 interp_direction = p2 - p1;
+                        p3 = p2 + interp_direction * 2.0f;
+                    } else {
+                        // We're fine - use the point after the target for p3
+                        p2 = path.points[pathmove->current_point_index + 1];
+                        p3 = path.points[pathmove->current_point_index + 2];
+                    }
+
+                    if (pathmove->current_point_index == 0) {
+                        // We're at the first point, so the point before this needs to be interpolated.
+                        // We interpolate linearly along the line from this to the next point (backwards).
+                        glm::vec3 interp_direction = path.points[pathmove->current_point_index] - path.points[pathmove->current_point_index + 1];
+                        p0 = path.points[pathmove->current_point_index] + interp_direction;
+                    } else {
+                        // We're fine - use the point before the current point
+                        p0 = path.points[pathmove->current_point_index - 1];
+                    }
+
+                    // Calculate the point on the spline
+                    glm::vec3 point = catmul(0.5f,
+                            p0,
+                            p1,
+                            p2,
+                            p3,
+                            pathmove->time_passed);
+                    
+                    // Apply
                     transform->set_position(point);
+
+                    // FIXME: Debugging output
+                    std::cout << point.x << ", " << point.y << ", " << point.z << std::endl;
                 });
     }
 

main.cpp

@@ -91,7 +91,15 @@ int main() {
     //player->assign<Movement>(glm::vec3(2.f, 2.f, 2.f));
     //player->assign<MouseLook>(0.1);
     player->assign<Camera>(70.0f, 1280, 720, 0.1f, 100.0f);
-    player->assign<PathMove>(10.0);
+    player->assign<PathMove>(10.0, PathMove::Path(std::vector<glm::vec3>{
+            glm::vec3(0.0, 2.0, 0.0),
+            glm::vec3(0.0, 2.0, 1.0),
+            glm::vec3(2.0, 2.0, 2.0),
+            glm::vec3(1.0, 3.0, 3.0),
+            glm::vec3(-2.0, 2.0, 4.0),
+            glm::vec3(2.0, 2.0, 4.0),
+            glm::vec3(0.0, 2.0, 10.0)
+        }));
     player->get<Transform>()->translate(glm::vec3(0.0f, 1.0f, 2.0f));
 
     Entity *monkey = world->create();