Now points move towards a cursor via a click

src/app.cpp

@@ -24,13 +24,13 @@ App* app_init(App_config conf) {
     }
     app->conf = conf;
     
-    app->mouse = new_mouse(Vec2{0, 0}, 30);
+    app->mouse = new_mouse(Vec2{0, 0}, 50);
     app->window = new_window(conf.win_name, conf.window_dimensions);
     app->cloth = new_cloth(
         conf.cloth_startpos,
         conf.cloth_dimensions,
         conf.cloth_spacing,
-        conf.efficiency_factor,
+        conf.efficiency_factor, 
         conf.friction_factor,
         Vec2{0, 0}, Vec2{app->window->dimensions.x-5, app->window->dimensions.y-5}
     );
@@ -66,13 +66,13 @@ void app_handle_input(App* app) {
                     break; 
                 
                 case SDLK_LEFT:
-                    if (app->conf.timestep >= 0.25) {
-                        app->conf.timestep -= 0.25;
+                    if (app->conf.timestep >= 0.15f) {
+                        app->conf.timestep -= 0.15f;
                     }
                     break;
                 
                 case SDLK_RIGHT:
-                    app->conf.timestep += 0.25;
+                    app->conf.timestep += 0.15f;
                     break;
             }
 

src/cloth.cpp

@@ -37,7 +37,7 @@ Cloth* new_cloth(
             };
             new_cloth->points.push_back(new_point);
 
-            if (x > 0) {
+            if (x != 0) {
                 Point* p0_left = new_cloth->points[new_cloth->points.size() - 2];
                 Connection* new_conn = new Connection{*p0_left, *new_point};
                 new_cloth->connections.push_back(new_conn);
@@ -77,11 +77,7 @@ void destroy_cloth(Cloth* cloth) {
 // calculate forces, move points and satisfy constraints 
 void cloth_step(Cloth* cloth, Mouse* mouse, Vec2f gravity_vec, float timedelta) {
     for (Point* p : cloth->points) {
-        if (p->frozen) {
-            continue;
-        }
-
-        // handle mouse
+        // check if this point is in pointer's area 
         // ((x0 - x1)^2 + (y0 - y1)^2)^0.5
         float distance_to_point = std::sqrt(pow(p->pos.x - mouse->pos.x, 2.0f)+pow(p->pos.y - mouse->pos.y, 2.0f));
         if (distance_to_point <= mouse->cursor_radius_size) {
@@ -90,23 +86,34 @@ void cloth_step(Cloth* cloth, Mouse* mouse, Vec2f gravity_vec, float timedelta)
             p->selected = false;
         }
 
-        if (p->selected && mouse->left_button_clicked) {
-            p->pos = Vec2f{(float) mouse->pos.x, (float) mouse->pos.y};
+        // skip any calculations if this point is frozen
+        if (p->frozen) {
+            continue;
         }
 
         // calculate velocity
-        p->velocity.x = (p->velocity.x + (gravity_vec.x/p->mass)) * timedelta;
-        p->velocity.y = (p->velocity.y + (gravity_vec.y/p->mass)) * timedelta;
+        p->acceleration.x = gravity_vec.x / p->mass;
+        p->acceleration.y = gravity_vec.y / p->mass;
 
-        // move point
-        p->pos.x += p->velocity.x;
-        p->pos.y += p->velocity.y;
+        if (p->selected && mouse->left_button_clicked) {
+            Vec2f difference = {
+                (float) (mouse->pos.x - p->pos.x) * cloth->efficiency_factor,
+                (float) (mouse->pos.y - p->pos.y) * cloth->efficiency_factor,
+            };
+
+            p->acceleration.x = difference.x / p->mass;
+            p->acceleration.y = difference.y / p->mass;
+        }
+
+        // apply calculated velocity
+        p->velocity.x = p->velocity.x + p->acceleration.x * timedelta;
+        p->velocity.y = p->velocity.y + p->acceleration.y * timedelta;
 
         // now handle constraints
         // bottom
         if (p->pos.y >= cloth->constraint_bottom_right.y) {
-            p->pos.y = cloth->constraint_bottom_right.y;            
-            p->velocity.x = (p->velocity.x * cloth->friction_factor);
+            p->pos.y = cloth->constraint_bottom_right.y; 
+            p->velocity.x = p->velocity.x * cloth->friction_factor; // friction on the floor
             p->velocity.y = -p->velocity.y * cloth->efficiency_factor;
         }
 
@@ -127,5 +134,9 @@ void cloth_step(Cloth* cloth, Mouse* mouse, Vec2f gravity_vec, float timedelta)
             p->pos.y = cloth->constraint_top_left.y;
             p->velocity.y = -p->velocity.y * cloth->efficiency_factor;
         }
+        
+        // move point
+        p->pos.x += p->velocity.x;
+        p->pos.y += p->velocity.y;
     }
 }

src/main.cpp

@@ -64,11 +64,11 @@ int main(const int argc, char** argv) {
 
     App_config config = {
         .win_name = window_name.c_str(),
-        .window_dimensions = Vec2{800, 700},
+        .window_dimensions = Vec2{750, 700},
         .cloth_startpos = Vec2{50, 50},
         .cloth_dimensions = Vec2{400, 400},
         .cloth_spacing = 20,
-        .gravity = Vec2f{0.5f, 0.75f},
+        .gravity = Vec2f{0.65f, 0.85f},
         .efficiency_factor = 0.25f,
         .timestep = 1.0f,
         .background_color = RGB{205, 222, 242},

src/point.hpp

@@ -9,5 +9,6 @@ struct Point {
     bool frozen;
     bool selected;
     float radius;
+    Vec2f acceleration;
     Vec2f velocity;
 };