Somewhat cloth-like feel

src/app.cpp

@@ -24,7 +24,7 @@ App* app_init(App_config conf) {
     }
     app->conf = conf;
     
-    app->mouse = new_mouse(Vec2{0, 0}, 50);
+    app->mouse = new_mouse(Vec2{0, 0}, conf.cursor_radius);
     app->window = new_window(conf.win_name, conf.window_dimensions);
     app->cloth = new_cloth(
         conf.cloth_startpos,

src/app.hpp

@@ -15,6 +15,7 @@ struct App_config {
     float efficiency_factor;
     float friction_factor;
     float timestep;
+    float cursor_radius;
     RGB background_color;
     RGB point_color;
     RGB point_selected_color;

src/cloth.cpp

@@ -4,6 +4,7 @@
 #include <cmath>
 #include <cstddef>
 #include <cstdio>
+#include <math.h>
 #include <vector>
 
 Cloth* new_cloth(
@@ -39,13 +40,33 @@ Cloth* new_cloth(
 
             if (x != 0) {
                 Point* p0_left = new_cloth->points[new_cloth->points.size() - 2];
-                Connection* new_conn = new Connection{*p0_left, *new_point};
+                float length = std::sqrt(
+                    pow(p0_left->pos.x - new_point->pos.x, 2.0f)+
+                    pow(p0_left->pos.y - new_point->pos.y, 2.0f)
+                );
+                
+                Connection* new_conn = new Connection{
+                    .p0 = *p0_left,
+                    .p1 = *new_point,
+                    .initial_length = length,
+                    .length = length,
+                };
                 new_cloth->connections.push_back(new_conn);
             }
 
             if (y != 0) {
                 Point* p0_up = new_cloth->points[new_cloth->points.size()-1 - dimensions.x/spacing];
-                Connection* new_conn = new Connection{*p0_up, *new_point};
+                float length = std::sqrt(
+                    pow(p0_up->pos.x - new_point->pos.x, 2.0f)+
+                    pow(p0_up->pos.y - new_point->pos.y, 2.0f)
+                );
+
+                Connection* new_conn = new Connection{
+                    .p0 = *p0_up,
+                    .p1 = *new_point,
+                    .initial_length = length,
+                    .length = length,
+                };
                 new_cloth->connections.push_back(new_conn);
             }
         }
@@ -139,4 +160,24 @@ void cloth_step(Cloth* cloth, Mouse* mouse, Vec2f gravity_vec, float timedelta)
         p->pos.x += p->velocity.x;
         p->pos.y += p->velocity.y;
     }
+
+    for (Connection* c : cloth->connections) {
+        if (c->p0.frozen || c->p1.frozen) {
+            continue;
+        }
+
+        float distance = std::sqrt(
+            std::pow(c->p0.pos.x - c->p1.pos.x, 2.0f) +
+            std::pow(c->p0.pos.y - c->p1.pos.y, 2.0f)
+        );
+        float diff_factor = (c->length - distance) / distance;
+
+        Vec2f offset = {
+            (c->p0.pos.x - c->p1.pos.x) * diff_factor * 0.75f,
+            (c->p0.pos.y - c->p1.pos.y) * diff_factor * 0.75f
+        };
+
+        c->p0.pos = Vec2f{c->p0.pos.x + offset.x, c->p0.pos.y + offset.y};
+        c->p1.pos = Vec2f{c->p1.pos.x - offset.x, c->p1.pos.y - offset.y};
+    }
 }

src/cloth.hpp

@@ -9,6 +9,7 @@
 struct Cloth {
     float efficiency_factor;
     float friction_factor;
+    float rigidity;
     Vec2 startpos;
     Vec2 dimensions;
     Vec2 constraint_top_left;

src/connection.hpp

@@ -5,4 +5,7 @@
 struct Connection {
     Point& p0;
     Point& p1;
+    float rigidity;
+    float initial_length;
+    float length;
 };

src/main.cpp

@@ -68,9 +68,10 @@ int main(const int argc, char** argv) {
         .cloth_startpos = Vec2{50, 50},
         .cloth_dimensions = Vec2{400, 400},
         .cloth_spacing = 20,
-        .gravity = Vec2f{0.65f, 0.85f},
+        .gravity = Vec2f{0.45f, 0.65f},
         .efficiency_factor = 0.25f,
         .timestep = 1.0f,
+        .cursor_radius = 75.0f,
         .background_color = RGB{205, 222, 242},
         .point_color = RGB{2, 10, 1},
         .point_selected_color = RGB{200, 40, 12},