set aim joint correction rate dynamically based on dt

src/config.h

@@ -33,6 +33,7 @@
 #define SPACE_CELL_BUCKETS_SQRT (256)
 #define SPACE_CELL_SIZE 1.0f
 
+
 #define GAME_FPS 50.0
 #define GAME_TIMESCALE 1
 

src/game.c

@@ -229,7 +229,6 @@ INTERNAL void spawn_test_entities(void)
     }
 
     /* Enemy */
-#if 1
     {
         struct entity *e = entity_alloc(root);
 
@@ -249,7 +248,6 @@ INTERNAL void spawn_test_entities(void)
         e->linear_ground_friction = 250;
         e->angular_ground_friction = 200;
     }
-#endif
 
 
     /* Big box */
@@ -984,12 +982,15 @@ INTERNAL void game_update(struct game_cmd_array game_cmds)
                 struct phys_motor_joint_def def = ZI;
                 def.e0 = joint_ent->handle;  /* Re-using joint entity as e0 */
                 def.e1 = ent->handle;
-                def.correction_rate = 0.1f;
                 def.max_force = 0;
                 def.max_torque = ent->control_torque;
                 joint_ent->motor_joint_data = motor_joint_from_def(def);
             }
 
+            /* Set correction rate dynamically since motor velocity is only set for one frame */
+            joint_ent->motor_joint_data.correction_rate = 10 * dt;
+
+
             /* Solve for final angle using law of sines */
             f32 new_angle;
             {
@@ -1039,6 +1040,7 @@ INTERNAL void game_update(struct game_cmd_array game_cmds)
                 struct xform joint_xf = entity_get_xform(joint_ent);
                 f32 diff = math_unwind_angle(new_angle - xform_get_rotation(joint_xf));
                 if (math_fabs(diff) > angle_error_allowed) {
+                    /* Instantly snap joint ent to new angle */
                     new_vel = diff / dt;
                 }
             }

src/mixer.h

@@ -50,6 +50,5 @@ void mixer_set_listener(struct v2 pos, struct v2 dir);
 
 /* Mixing */
 struct mixed_pcm_f32 mixer_update(struct arena *arena, u64 frame_request_count);
-void mixer_advance(u64 frames_written_count);
 
 #endif

src/phys.c

@@ -717,23 +717,23 @@ void phys_solve_motor_joints(struct phys_ctx *ctx, f32 dt)
         f32 w0 = e0->angular_velocity;
         f32 w1 = e1->angular_velocity;
 
-        f32 correction_rate = joint->correction_rate / dt;
+        f32 correction_rate = joint->correction_rate;
+        f32 inv_dt = 1.f / dt;
 
         /* Angular constraint */
         {
             f32 max_impulse = joint->max_torque * dt;
-
             f32 angular_separation = math_unwind_angle(xform_get_rotation(e1_xf) - xform_get_rotation(e0_xf));
-            f32 angular_bias = angular_separation * correction_rate;
 
-            f32 impulse = -joint->angular_mass * (w1 - w0 + angular_bias);
+            f32 angular_bias = angular_separation * correction_rate * inv_dt;
 
             f32 old_impulse = joint->angular_impulse;
-            joint->angular_impulse = clamp_f32(joint->angular_impulse + impulse, -max_impulse, max_impulse);
+            f32 new_impulse = clamp_f32(old_impulse + (-joint->angular_mass * (w1 - w0 + angular_bias)), -max_impulse, max_impulse);
-            impulse = joint->angular_impulse - old_impulse;
+            joint->angular_impulse = new_impulse;
 
-            w0 -= impulse * inv_i0;
+            f32 delta = new_impulse - old_impulse;
-            w1 += impulse * inv_i1;
+            w0 -= delta * inv_i0;
+            w1 += delta * inv_i1;
         }
 
         /* Linear constraint */
@@ -744,19 +744,20 @@ void phys_solve_motor_joints(struct phys_ctx *ctx, f32 dt)
             f32 max_impulse = joint->max_force * dt;
 
             struct v2 linear_separation = v2_sub(v2_add(e1_xf.og, vcp1), v2_add(e0_xf.og, vcp0));
-            struct v2 linear_bias = v2_mul(linear_separation, correction_rate);
+            struct v2 linear_bias = v2_mul(linear_separation, correction_rate * inv_dt);
 
             struct v2 vrel = v2_sub(v2_add(v1, v2_perp_mul(vcp1, w1)), v2_add(v0, v2_perp_mul(vcp0, w0)));
             struct v2 impulse = v2_neg(xform_basis_mul_v2(joint->linear_mass_xf, v2_add(vrel, linear_bias)));
 
             struct v2 old_impulse = joint->linear_impulse;
-            joint->linear_impulse = v2_clamp_len(v2_add(joint->linear_impulse, impulse), max_impulse);
+            struct v2 new_impulse = v2_clamp_len(v2_add(old_impulse, impulse), max_impulse);
-            impulse = v2_sub(joint->linear_impulse, old_impulse);
+            joint->linear_impulse = new_impulse;
 
-            v0 = v2_sub(v0, v2_mul(impulse, inv_m0));
+            struct v2 delta = v2_sub(new_impulse, old_impulse);
-            v1 = v2_add(v1, v2_mul(impulse, inv_m1));
+            v0 = v2_sub(v0, v2_mul(delta, inv_m0));
-            w0 -= v2_wedge(vcp0, impulse) * inv_i0;
+            v1 = v2_add(v1, v2_mul(delta, inv_m1));
-            w1 += v2_wedge(vcp1, impulse) * inv_i1;
+            w0 -= v2_wedge(vcp0, delta) * inv_i0;
+            w1 += v2_wedge(vcp1, delta) * inv_i1;
         }
 
         entity_set_linear_velocity(e0, v0);

src/user.c

@@ -936,7 +936,7 @@ INTERNAL void user_update(void)
 
             b32 skip_debug_draw = !G.debug_camera && ent == active_camera;
             b32 skip_debug_draw_transform = entity_has_prop(ent, ENTITY_PROP_CAMERA);
-            skip_debug_draw_transform = true;
+            //skip_debug_draw_transform = true;
 
             struct xform sprite_xform = xf;
 
@@ -1005,8 +1005,8 @@ INTERNAL void user_update(void)
 
                 /* Draw xform */
                 if (!skip_debug_draw_transform) {
-                    u32 color_x = RGBA_32_F(1, 0, 0, 0.3);
+                    u32 color_x = RGBA_32_F(1, 0, 0, 0.5);
-                    u32 color_y = RGBA_32_F(0, 1, 0, 0.3);
+                    u32 color_y = RGBA_32_F(0, 1, 0, 0.5);
                     debug_draw_xform(xf, color_x, color_y);
                 }