Implement collision groups, category and masks

examples/chains.c

@@ -29,8 +29,11 @@ void setup(Example *example) {
             (nv_Material){1.0, 0.0, 0.0},
             width, height
         );
-
+        chain_part->collision_group = 1;
         nv_Space_add(example->space, chain_part);
+
+        // Temporary solution to avoid constraints exploding
+        nv_Body_apply_force(chain_part, NV_VEC2((nv_float)(i%10)*50.0, 0.0)); 
     }
 
     // Link chain parts
@@ -69,10 +72,10 @@ void setup(Example *example) {
             (nv_Material){1.0, 0.0, 0.0},
             radius
         );
-
+        chain_part->collision_group = 2;
         nv_Space_add(example->space, chain_part);
 
-        // Temporary solution to circle chain going crazy
+        // Temporary solution to avoid constraints exploding
         nv_Body_apply_force(chain_part, NV_VEC2((nv_float)(i%10)*50.0, 0.0)); 
     }
 
@@ -110,7 +113,7 @@ void setup(Example *example) {
             (nv_Material){1.0, 0.0, 0.0},
             size, size / 3.0
         );
-
+        chain_part->collision_group = 3;
         nv_Space_add(example->space, chain_part);
     }
 

examples/example_base.h

@@ -1909,7 +1909,7 @@ void Example_run(Example *example) {
         nv_Material_WOOD,
         0.3
     );
-    mouse_body->collision = false;
+    mouse_body->enable_collision = false;
     nv_Space_add(example->space, mouse_body);
     nv_Array_add(example->sprites, NULL);
 
@@ -2184,7 +2184,7 @@ void Example_run(Example *example) {
                         nv_Material_WOOD,
                         0.3
                     );
-                    mouse_body->collision = false;
+                    mouse_body->enable_collision = false;
                     nv_Space_add(example->space, mouse_body);
 
                     example->counter = 0;

examples/spring_car.c

@@ -13,10 +13,10 @@
 
 void update(Example *example) {
     if (example->keys[SDL_SCANCODE_LEFT] || example->keys[SDL_SCANCODE_RIGHT]) {
-        nv_Body *wheel1 = (nv_Body *)example->space->bodies->data[4];
+        nv_Body *wheel1 = (nv_Body *)example->space->bodies->data[6];
         nv_Body *wheel2 = (nv_Body *)example->space->bodies->data[5];
 
-        double strength = 7.0 * 1e2;
+        double strength = 12.0 * 1e2;
         double limit = 30.0;
 
         if (example->keys[SDL_SCANCODE_LEFT]) {
@@ -82,26 +82,26 @@ void setup(Example *example) {
 
     // Create wheels
 
-    nv_Material wheel_mat = (nv_Material){1.5, 0.8, 3.0};
+    nv_Material wheel_mat = (nv_Material){1.5, 0.7, 3.0};
 
     nv_Body *wheel1 = nv_Circle_new(
         nv_BodyType_DYNAMIC,
-        NV_VEC2(49.0, 40.0),
+        NV_VEC2(53.0, 32.0),
         0.0,
         wheel_mat,
-        1.5
+        2.0
     );
-
+    wheel1->collision_group = 1;
     nv_Space_add(example->space, wheel1);
 
     nv_Body *wheel2 = nv_Circle_new(
         nv_BodyType_DYNAMIC,
-        NV_VEC2(61.0, 40.0),
+        NV_VEC2(57.0, 32.0),
         0.0,
         wheel_mat,
-        1.5
+        2.0
     );
-
+    wheel2->collision_group = 1;
     nv_Space_add(example->space, wheel2);
 
 
@@ -113,53 +113,53 @@ void setup(Example *example) {
         (nv_Material){4.0, 0.3, 0.5},
         10.0, 3.0
     );
-
+    body->collision_group = 1;
     nv_Space_add(example->space, body);
 
 
     // Create spring constraints
 
-    double suspension_length = 2.5;
-    double suspension_strength = 1500.0;
+    double suspension_length = 2.3;
+    double suspension_strength = 2700.0;
     double suspension_damping = 150.00;
 
     nv_Constraint *spring1 = nv_Spring_new(
         wheel1, body,
-        NV_VEC2(0.0, 0.0), NV_VEC2(-4.0, 1.5),
+        NV_VEC2(0.0, 0.0), NV_VEC2(-4.0, 0.0),
         suspension_length,
-        suspension_strength,
+        suspension_strength * 1.0,
         suspension_damping
     );
 
     nv_Space_add_constraint(example->space, spring1);
 
     nv_Constraint *spring2 = nv_Spring_new(
         wheel1, body,
-        NV_VEC2(0.0, 0.0), NV_VEC2(-1.5, 1.5),
+        NV_VEC2(0.0, 0.0), NV_VEC2(-1.5, 0.0),
         suspension_length,
-        suspension_strength * 3.0,
-        suspension_damping
+        suspension_strength * 6.0,
+        suspension_damping * 2.0
     );
 
 
     nv_Space_add_constraint(example->space, spring2);
 
     nv_Constraint *spring3 = nv_Spring_new(
         wheel2, body,
-        NV_VEC2(0.0, 0.0), NV_VEC2(4.0, 1.5),
+        NV_VEC2(0.0, 0.0), NV_VEC2(4.0, 0.0),
         suspension_length,
-        suspension_strength,
+        suspension_strength * 1.0,
         suspension_damping
     );
 
     nv_Space_add_constraint(example->space, spring3);
 
     nv_Constraint *spring4 = nv_Spring_new(
         wheel2, body,
-        NV_VEC2(0.0, 0.0), NV_VEC2(1.5, 1.5),
+        NV_VEC2(0.0, 0.0), NV_VEC2(1.5, 0.0),
         suspension_length,
-        suspension_strength * 3.0,
-        suspension_damping
+        suspension_strength * 6.0,
+        suspension_damping * 2.0
     );
 
     nv_Space_add_constraint(example->space, spring4);

include/novaphysics/body.h

@@ -103,7 +103,11 @@ typedef struct {
 
     bool is_attractor; /**< Flag reporting if the body is an attractor. */
 
-    bool collision;
+    bool enable_collision; /**< Whether to collide this body with other bodies or not. */
+    nv_uint32 collision_group; /**< Collision group of the body.
+                                    Bodies that share the same non-zero group do not collide. */
+    nv_uint32 collision_category; /**< Bitmask defining this body's collision category. */
+    nv_uint32 collision_mask; /**< Bitmask defining this body's collision mask. */
 } nv_Body;
 
 /**

src/body.c

@@ -66,7 +66,10 @@ nv_Body *nv_Body_new(
 
     body->is_attractor = false;
 
-    body->collision = true;
+    body->enable_collision = true;
+    body->collision_group = 0;
+    body->collision_category = 0b11111111111111111111111111111111;
+    body->collision_mask = 0b11111111111111111111111111111111;
 
     nv_Body_calc_mass_and_inertia(body);
 

src/broadphase.c

@@ -30,7 +30,7 @@ static inline bool nv_BroadPhase_early_out(nv_Space *space, nv_Body *a, nv_Body
     if (a == b)
         return true;
 
-    if (!a->collision || !b->collision)
+    if (!a->enable_collision || !b->enable_collision)
         return true;
 
     // Two static bodies do not need to interact
@@ -48,6 +48,15 @@ static inline bool nv_BroadPhase_early_out(nv_Space *space, nv_Body *a, nv_Body
             return true;
     }
 
+    // Bodies share the same non-zero group
+    if (a->collision_group == b->collision_group && a->collision_group != 0)
+        return true;
+
+    // One of the collision mask doesn't fit the category
+    if (a->collision_mask & b->collision_category == 0 ||
+        b->collision_mask & a->collision_category == 0)
+        return true;
+
     return false;
 }