revert to using euler integration

src/entity.c

@@ -16,7 +16,6 @@ READONLY struct entity _g_entity_nil = {
     .local_xform = XFORM_IDENT_NOCAST,
     .cached_global_xform = XFORM_IDENT_NOCAST,
     .cached_global_xform_dirty = false,
-    .verlet_xform = XFORM_IDENT_NOCAST,
     .mass_unscaled = 1,
     .sprite_local_xform = XFORM_IDENT_NOCAST,
     .sprite_tint = COLOR_WHITE
@@ -27,7 +26,6 @@ GLOBAL READONLY struct entity g_entity_default = {
     .local_xform = XFORM_IDENT_NOCAST,
     .cached_global_xform = XFORM_IDENT_NOCAST,
     .cached_global_xform_dirty = true,
-    .verlet_xform = XFORM_IDENT_NOCAST,
     .mass_unscaled = 1,
     .sprite_local_xform = XFORM_IDENT_NOCAST,
     .sprite_tint = COLOR_WHITE

src/entity.h

@@ -148,8 +148,8 @@ struct entity {
     f32 mass_unscaled;  /* Mass of entity in kg before any transformations */
     f32 ground_friction;
 
-    /* Xform of the entity from the previous frame (used to calculate velocity) */
+    struct v2 linear_velocity;  /* m/s */
-    struct xform verlet_xform;
+    //f32 angular_velocity;       /* rad/s */
 
     /* ====================================================================== */
     /* Impulse */

src/game.c

@@ -105,7 +105,6 @@ INTERNAL void activate_now(struct entity *ent)
 {
     entity_enable_prop(ent, ENTITY_PROP_ACTIVE);
     ent->activation_tick = G.tick.tick_id;
-    ent->verlet_xform = entity_get_xform(ent);
     ++ent->continuity_gen;
 }
 
@@ -596,9 +595,7 @@ INTERNAL void game_update(struct game_cmd_array game_cmds)
         if (!(ent->valid && entity_has_prop(ent, ENTITY_PROP_ACTIVE))) continue;
         if (!entity_has_prop(ent, ENTITY_PROP_PHYSICAL)) continue;
         if (ent->ground_friction != 0) {
-            struct xform verlet_xform = ent->verlet_xform;
+            struct v2 linear_velocity = ent->linear_velocity;
-            struct xform xf = entity_get_xform(ent);
-            struct v2 linear_velocity = v2_div(v2_sub(xf.og, verlet_xform.og), dt);
 
             if (!v2_eq(linear_velocity, V2(0, 0))) {
                 /* FIXME: Incorrect behavior at low FPS & low entity density */
@@ -612,6 +609,7 @@ INTERNAL void game_update(struct game_cmd_array game_cmds)
                     activate_now(force);
                 } else {
                     /* If linear_velocity is below clamp_epsilon, stop entity movement. */
+                    struct xform xf = entity_get_xform(ent);
                     f32 mass = ent->mass_unscaled * math_fabs(xform_get_determinant(xf));
                     struct entity *impulse = entity_alloc(ent);
                     entity_enable_prop(impulse, ENTITY_PROP_IMPULSE);
@@ -635,25 +633,24 @@ INTERNAL void game_update(struct game_cmd_array game_cmds)
         f32 mass = ent->mass_unscaled * math_fabs(xform_get_determinant(xf));
 
         /* Determine acceleration from forces and impulses */
-        struct v2 acceleration = V2(0, 0);
+        struct v2 tick_acceleration = V2(0, 0);
         for (struct entity *child = entity_from_handle(store, ent->first); child->valid; child = entity_from_handle(store, child->next)) {
             if (entity_has_prop(child, ENTITY_PROP_IMPULSE)) {
-                acceleration = v2_add(acceleration, child->force);
+                tick_acceleration = v2_add(tick_acceleration, child->force);
                 entity_enable_prop(child, ENTITY_PROP_RELEASE);
             } else if (entity_has_prop(child, ENTITY_PROP_FORCE)) {
-                acceleration = v2_add(acceleration, v2_mul(child->force, dt));
+                tick_acceleration = v2_add(tick_acceleration, v2_mul(child->force, dt));
                 entity_enable_prop(child, ENTITY_PROP_RELEASE);
             }
         }
-        acceleration = v2_div(acceleration, mass);
+        tick_acceleration = v2_div(tick_acceleration, mass);
-
-        /* Verlet integration */
-        struct v2 tick_velocity = v2_sub(xf.og, ent->verlet_xform.og);
-        tick_velocity = v2_add(tick_velocity, v2_mul(acceleration, dt));
-        ent->verlet_xform = xf;
 
+        /* Integrate */
+        struct v2 tick_velocity = v2_mul(ent->linear_velocity, dt);
+        tick_velocity = v2_add(tick_velocity, v2_mul(tick_acceleration, dt));
         xf.og = v2_add(xf.og, tick_velocity);
         ent->predicted_xform = xf;
+        ent->linear_velocity = v2_div(tick_velocity, dt);
     }
 
     /* ========================== *
@@ -882,7 +879,6 @@ INTERNAL void game_update(struct game_cmd_array game_cmds)
 
             struct xform xf = XFORM_TRS(.t = pos, .r = v2_angle(velocity) + PI / 2);
             entity_set_xform(ent, xf);
-            ent->verlet_xform = xf;
             entity_enable_prop(ent, ENTITY_PROP_PHYSICAL);
 
             /* Create impulse */

src/gjk.c

@@ -286,7 +286,7 @@ struct gjk_extended_result gjk_extended(struct v2_array shape0, struct v2_array
 
             /* Insert point into prototype */
             /* FIXME: Preserve winding order */
-            arena_push(scratch.arena, struct v2);
+            arena_push(scratch.arena, struct gjk_menkowski_point);
             ++proto_count;
             for (u32 i = proto_count - 1; i > pen_pe_index; --i) {
                 u32 shift_from = (i > 0) ? i - 1 : proto_count - 1;
@@ -685,7 +685,7 @@ struct gjk_extended_result gjk_extended(struct v2_array shape0, struct v2_array
 
                 /* Insert point into prototype */
                 /* FIXME: Preserve winding order */
-                arena_push(scratch.arena, struct v2);
+                arena_push(scratch.arena, struct gjk_menkowski_point);
                 ++proto_count;
                 for (u32 i = proto_count - 1; i > pen_pe_index; --i) {
                     u32 shift_from = (i > 0) ? i - 1 : proto_count - 1;

src/user.c

@@ -393,7 +393,7 @@ INTERNAL void debug_draw_movement(struct entity *ent)
     u32 color_vel = RGBA_32_F(1, 0.5, 0, 1);
 
     struct xform xf = entity_get_xform(ent);
-    struct v2 velocity = v2_div(v2_sub(xf.og, ent->verlet_xform.og), G.world.dt);
+    struct v2 velocity = ent->linear_velocity;
 
     struct v2 pos       = xform_mul_v2(G.world_view, xf.og);
     struct v2 vel_ray   = xform_basis_mul_v2(G.world_view, velocity);
@@ -498,6 +498,9 @@ INTERNAL void user_update(void)
 
                     e->control_move_force = math_lerp(e0->control_move_force, e1->control_move_force, tick_blend);
 
+                    e->linear_velocity = v2_lerp(e0->linear_velocity, e1->linear_velocity, tick_blend);
+                    e->angular_velocity = math_lerp(e0->angular_velocity, e1->angular_velocity, tick_blend);
+
                     e->control.move = v2_lerp(e0->control.move, e1->control.move, tick_blend);
                     e->control.focus = v2_lerp(e0->control.focus, e1->control.focus, tick_blend);