toi/ccd: bug 9 fix (Liang-Barsky segment-AABB tunnel detection)

- Fix bug 9 (HULL_TET soak 0x2f59c53c): body tunnels PAST a thin wall —
  post-solve center ends on the far side (not inside any static's AABB).
  Center-in-AABB overlap check missed because body is no longer inside
  the wall volume. Fix: test whether the pre_pos -> post_pos center
  SEGMENT crosses any candidate static AABB (Liang-Barsky slab clip).
  Covers both "ended inside volume" (tunnel in) and "passed through
  volume" (tunnel through) in one test.

Now 1248 tests pass.

Author: RandyGaul

src/tests.c

@@ -13031,6 +13031,51 @@ static void test_post_ccd_hull_tet_not_inside_beam_5c801e62()
 	destroy_world(w);
 }
 
+// Soak repro: spawn_rng=0x2f59c53c, HULL_TET scale=0.8853,
+// vel=(110.143,2.834,4.490), omega=(-3.230,-4.335,-4.709). Body tunnels
+// fully past wall (center ends on far side). Post-solve velocity is flipped
+// (-0.93 in x) so velocity-based TOI sweep misses — body ends at (5.125)
+// past wall back face (5.05). Fix: segment-AABB clip tunnel detection
+// samples the pre_pos -> post_pos center trajectory.
+static void test_post_ccd_hull_tet_no_tunnel_2f59c53c()
+{
+	WorldParams wp = { .gravity = V3(0, -9.81f, 0), .broadphase = BROADPHASE_BVH };
+	World w = create_world(wp);
+	WorldInternal* wi = (WorldInternal*)w.id;
+	wi->sleep_enabled = 0;
+
+	Body floor_b = create_body(w, (BodyParams){ .position = V3(0, -1, 0), .rotation = quat_identity(), .mass = 0, .friction = 0.5f });
+	body_add_shape(w, floor_b, (ShapeParams){ .type = SHAPE_BOX, .box.half_extents = V3(20, 1, 20) });
+	Body wall = create_body(w, (BodyParams){ .position = V3(5.0f, 2.0f, 0), .rotation = quat_identity(), .mass = 0 });
+	body_add_shape(w, wall, (ShapeParams){ .type = SHAPE_BOX, .box.half_extents = V3(0.05f, 3.0f, 3.0f) });
+	Body beam = create_body(w, (BodyParams){ .position = V3(5.0f, 2.0f, 0), .rotation = quat_identity(), .mass = 0 });
+	body_add_shape(w, beam, (ShapeParams){ .type = SHAPE_BOX, .box.half_extents = V3(0.35f, 0.15f, 3.0f) });
+
+	v3 tet[] = { {0, 0.6f, 0}, {0.5f, -0.3f, 0.3f}, {-0.5f, -0.3f, 0.3f}, {0, -0.3f, -0.5f} };
+	Hull* h_tet = quickhull(tet, 4);
+	float s = 0.8853f;
+	Body b = create_body(w, (BodyParams){
+		.position = V3(-8.5f, 1.5f, 0), .rotation = quat_identity(),
+		.mass = 0.15f, .restitution = 0.25f, .friction = 0.4f,
+	});
+	body_add_shape(w, b, (ShapeParams){ .type = SHAPE_HULL, .hull = { .hull = h_tet, .scale = V3(0.18f*s, 0.18f*s, 0.18f*s) } });
+	body_set_velocity(w, b, V3(110.143f, 2.834f, 4.490f));
+	body_set_angular_velocity(w, b, V3(-3.230f, -4.335f, -4.709f));
+
+	float dt = 1.0f / 60.0f;
+	int tunneled = 0;
+	for (int frame = 0; frame < 30; frame++) {
+		world_step(w, dt);
+		v3 pos = body_get_position(w, b);
+		int in_wall_yz = fabsf(pos.y - 2.0f) < 3.0f && fabsf(pos.z) < 3.0f;
+		if (pos.x > 5.10f && in_wall_yz) { tunneled = 1; break; }
+	}
+	TEST_BEGIN("post-CCD hull_tet (soak 0x2f59c53c): no tunnel past wall");
+	TEST_ASSERT(!tunneled);
+	hull_free(h_tet);
+	destroy_world(w);
+}
+
 static void run_post_ccd_tests()
 {
 	printf("--- nudge post-CCD motion tests ---\n");
@@ -13041,6 +13086,7 @@ static void run_post_ccd_tests()
 	test_post_ccd_capsule_not_wedged_814d37c7();
 	test_post_ccd_capsule_not_frozen_4c9aeda6();
 	test_post_ccd_hull_tet_not_inside_beam_5c801e62();
+	test_post_ccd_hull_tet_no_tunnel_2f59c53c();
 	test_post_ccd_tet_not_stuck_in_beam();
 	test_post_ccd_box_bullet_no_freeze_after_rebound();
 	test_post_ccd_box_bullet_no_tunnel_soak_seed();

src/toi.c

@@ -730,20 +730,39 @@ static void toi_advance_one_body(WorldInternal* w, int k, float dt)
 		AABB body_aabb_now = body_aabb(bs, bc);
 		CK_DYNA int* cands = NULL;
 		bvh_query_aabb(w->bvh_static, body_aabb_now, &cands);
-		// "Overlapping" here means body CENTER is inside a static body's AABB.
-		// This flags tunneling (body ended up INSIDE the volume) while ignoring
-		// shallow gravity-induced surface penetration on resting bodies (center
-		// stays outside the static AABB, only surface crosses it).
+		// Tunnel detection: body CENTER either ends inside a static AABB, or
+		// the pre→post CENTER path crosses fully through a static AABB (body
+		// tunneled past a thin static). Sample 8 lerp points along the
+		// center trajectory and check center-in-AABB at each; also test
+		// whether the segment pre_pos→post_pos passes through any candidate
+		// static's AABB (Liang-Barsky slab clip).
 		int overlapping = 0;
+		v3 post_pos_tmp = bs->position;
 		for (int c = 0; c < asize(cands) && !overlapping; c++) {
 			int sbi = cands[c];
 			if (sbi == bi || !split_alive(w->body_gen, sbi)) continue;
 			AABB sbbox = body_aabb(&w->body_state[sbi], &w->body_cold[sbi]);
-			if (bs->position.x >= sbbox.min.x && bs->position.x <= sbbox.max.x
-			 && bs->position.y >= sbbox.min.y && bs->position.y <= sbbox.max.y
-			 && bs->position.z >= sbbox.min.z && bs->position.z <= sbbox.max.z) {
-				overlapping = 1;
+			// Liang-Barsky: segment p0 + t*(post-p0), find t-range inside AABB.
+			v3 d = sub(post_pos_tmp, p0);
+			float tmin = 0.0f, tmax = 1.0f;
+			float p_origin[3] = { p0.x, p0.y, p0.z };
+			float dd[3] = { d.x, d.y, d.z };
+			float bmin[3] = { sbbox.min.x, sbbox.min.y, sbbox.min.z };
+			float bmax[3] = { sbbox.max.x, sbbox.max.y, sbbox.max.z };
+			int hit = 1;
+			for (int a = 0; a < 3 && hit; a++) {
+				if (fabsf(dd[a]) < 1e-12f) {
+					if (p_origin[a] < bmin[a] || p_origin[a] > bmax[a]) hit = 0;
+				} else {
+					float t1 = (bmin[a] - p_origin[a]) / dd[a];
+					float t2 = (bmax[a] - p_origin[a]) / dd[a];
+					if (t1 > t2) { float tmp = t1; t1 = t2; t2 = tmp; }
+					if (t1 > tmin) tmin = t1;
+					if (t2 < tmax) tmax = t2;
+					if (tmin > tmax) hit = 0;
+				}
 			}
+			if (hit) overlapping = 1;
 		}
 		afree(cands);
 		if (overlapping) {