src/world/world.cpp

   1 #include "Entity.hpp"
   2 #include "EntityController.hpp"
   3 #include "EntityDerivative.hpp"
   4 #include "EntityState.hpp"
   5 #include "Player.hpp"
   6 #include "World.hpp"
   7
   8 #include "ChunkIndex.hpp"
   9 #include "EntityCollision.hpp"
  10 #include "WorldCollision.hpp"
  11 #include "../app/Assets.hpp"
  12 #include "../geometry/const.hpp"
  13 #include "../geometry/distance.hpp"
  14 #include "../graphics/Format.hpp"
  15 #include "../graphics/Viewport.hpp"
  16
  17 #include <algorithm>
  18 #include <cmath>
  19 #include <iostream>
  20 #include <limits>
  21 #include <glm/gtx/euler_angles.hpp>
  22 #include <glm/gtx/io.hpp>
  23 #include <glm/gtx/projection.hpp>
  24 #include <glm/gtx/quaternion.hpp>
  25 #include <glm/gtx/rotate_vector.hpp>
  26 #include <glm/gtx/transform.hpp>
  27
  28
  29 namespace blank {
  30
  31 Entity::Entity() noexcept
  32 : ctrl(nullptr)
  33 , model()
  34 , id(-1)
  35 , name("anonymous")
  36 , bounds()
  37 , radius(0.0f)
  38 , state()
  39 , heading(0.0f, 0.0f, -1.0f)
  40 , max_vel(5.0f)
  41 , max_force(25.0f)
  42 , ref_count(0)
  43 , world_collision(false)
  44 , dead(false)
  45 , owns_controller(false) {
  46
  47 }
  48
  49 Entity::~Entity() noexcept {
  50         UnsetController();
  51 }
  52
  53 Entity::Entity(const Entity &other) noexcept
  54 : ctrl(other.ctrl)
  55 , model(other.model)
  56 , id(-1)
  57 , name(other.name)
  58 , bounds(other.bounds)
  59 , state(other.state)
  60 , model_transform(1.0f)
  61 , view_transform(1.0f)
  62 , speed(0.0f)
  63 , heading(0.0f, 0.0f, -1.0f)
  64 , max_vel(other.max_vel)
  65 , max_force(other.max_force)
  66 , ref_count(0)
  67 , world_collision(other.world_collision)
  68 , dead(other.dead)
  69 , owns_controller(false) {
  70
  71 }
  72
  73 void Entity::SetController(EntityController *c) noexcept {
  74         UnsetController();
  75         ctrl = c;
  76         owns_controller = true;
  77 }
  78
  79 void Entity::SetController(EntityController &c) noexcept {
  80         UnsetController();
  81         ctrl = &c;
  82         owns_controller = false;
  83 }
  84
  85 void Entity::UnsetController() noexcept {
  86         if (ctrl && owns_controller) {
  87                 delete ctrl;
  88         }
  89         ctrl = nullptr;
  90 }
  91
  92 glm::vec3 Entity::ControlForce(const EntityState &s) const noexcept {
  93         if (HasController()) {
  94                 return GetController().ControlForce(*this, s);
  95         } else {
  96                 return -s.velocity;
  97         }
  98 }
  99
 100 void Entity::Position(const glm::ivec3 &c, const glm::vec3 &b) noexcept {
 101         state.pos.chunk = c;
 102         state.pos.block = b;
 103 }
 104
 105 void Entity::Position(const glm::vec3 &pos) noexcept {
 106         state.pos.block = pos;
 107         state.AdjustPosition();
 108 }
 109
 110 void Entity::TurnHead(float dp, float dy) noexcept {
 111         SetHead(state.pitch + dp, state.yaw + dy);
 112 }
 113
 114 void Entity::SetHead(float p, float y) noexcept {
 115         state.pitch = p;
 116         state.yaw = y;
 117 }
 118
 119 glm::mat4 Entity::Transform(const glm::ivec3 &reference) const noexcept {
 120         return glm::translate(glm::vec3((state.pos.chunk - reference) * ExactLocation::Extent())) * model_transform;
 121 }
 122
 123 glm::mat4 Entity::ViewTransform(const glm::ivec3 &reference) const noexcept {
 124         return Transform(reference) * view_transform;
 125 }
 126
 127 Ray Entity::Aim(const ExactLocation::Coarse &chunk_offset) const noexcept {
 128         glm::mat4 transform = ViewTransform(chunk_offset);
 129         return Ray{ glm::vec3(transform[3]), -glm::vec3(transform[2]) };
 130 }
 131
 132 void Entity::Update(float dt) {
 133         UpdateTransforms();
 134         UpdateHeading();
 135         if (HasController()) {
 136                 GetController().Update(*this, dt);
 137         }
 138         UpdateModel(dt);
 139 }
 140
 141 void Entity::UpdateTransforms() noexcept {
 142         // model transform is the one given by current state
 143         model_transform = state.Transform(state.pos.chunk);
 144         // view transform is either the model's eyes transform or,
 145         // should the entity have no model, the pitch (yaw already is
 146         // in model transform)
 147         if (model) {
 148                 view_transform = model.EyesTransform();
 149         } else {
 150                 view_transform = toMat4(glm::quat(glm::vec3(state.pitch, state.yaw, 0.0f)));
 151         }
 152 }
 153
 154 void Entity::UpdateHeading() noexcept {
 155         speed = length(Velocity());
 156         if (speed > std::numeric_limits<float>::epsilon()) {
 157                 heading = Velocity() / speed;
 158         } else {
 159                 speed = 0.0f;
 160                 // use -Z (forward axis) of model transform (our "chest")
 161                 heading = -glm::vec3(model_transform[2]);
 162         }
 163 }
 164
 165 void Entity::UpdateModel(float dt) noexcept {
 166         // first, sanitize the pitch and yaw fields of state (our input)
 167         // those indicate the head orientation in the entity's local cosystem
 168         state.AdjustHeading();
 169         // TODO: this flickers horrible and also shouldn't be based on velocity, but on control force
 170         //OrientBody(dt);
 171         OrientHead(dt);
 172 }
 173
 174 void Entity::OrientBody(float dt) noexcept {
 175         // maximum body rotation per second (due to velocity orientation) (90°)
 176         constexpr float max_body_turn_per_second = PI_0p5;
 177         const float max_body_turn = max_body_turn_per_second * dt;
 178         // minimum speed to apply body correction
 179         constexpr float min_speed = 0.0625f;
 180         // use local Y as up
 181         const glm::vec3 up(model_transform[1]);
 182         if (speed > min_speed) {
 183                 // check if our orientation and velocity are aligned
 184                 const glm::vec3 forward(-model_transform[2]);
 185                 // facing is local -Z rotated about local Y by yaw and transformed into world space
 186                 const glm::vec3 facing(normalize(glm::vec3(glm::vec4(rotateY(glm::vec3(0.0f, 0.0f, -1.0f), state.yaw), 0.0f) * transpose(model_transform))));
 187                 // only adjust if velocity isn't almost parallel to up
 188                 float vel_dot_up = dot(Velocity(), up);
 189                 if (std::abs(1.0f - std::abs(vel_dot_up)) > std::numeric_limits<float>::epsilon()) {
 190                         // get direction of velocity projected onto model plane
 191                         glm::vec3 direction(normalize(Velocity() - (Velocity() * vel_dot_up)));
 192                         // if velocity points away from our facing (with a little bias), flip it around
 193                         // (the entity is "walking backwards")
 194                         if (dot(facing, direction) < -0.1f) {
 195                                 direction = -direction;
 196                         }
 197                         // calculate the difference between forward and direction
 198                         const float absolute_difference = std::acos(dot(forward, direction));
 199                         // if direction is clockwise with respect to up vector, invert the angle
 200                         const float relative_difference = dot(cross(forward, direction), up) < 0.0f
 201                                 ? -absolute_difference
 202                                 : absolute_difference;
 203                         // only correct by half the difference max
 204                         const float correction = glm::clamp(relative_difference * 0.5f, -max_body_turn, max_body_turn);
 205                         if (ID() == 1) {
 206                                 std::cout << "orientation before: " << state.orient << std::endl;
 207                                 std::cout << "up:        " << up << std::endl;
 208                                 std::cout << "forward:   " << forward << std::endl;
 209                                 std::cout << "facing:    " << facing << std::endl;
 210                                 std::cout << "direction: " << direction << std::endl;
 211                                 std::cout << "difference: " << glm::degrees(relative_difference) << "°" << std::endl;
 212                                 std::cout << "correction: " << glm::degrees(correction) << "°" << std::endl;
 213                                 std::cout << std::endl;
 214                         }
 215                         // now rotate body by correction and head by -correction
 216                         state.orient = rotate(state.orient, correction, up);
 217                         state.yaw -= correction;
 218                 }
 219         }
 220 }
 221
 222 void Entity::OrientHead(float dt) noexcept {
 223         // maximum yaw of head (60°)
 224         constexpr float max_head_yaw = PI / 3.0f;
 225         // use local Y as up
 226         const glm::vec3 up(model_transform[1]);
 227         // if yaw is bigger than max, rotate the body to accomodate
 228         if (std::abs(state.yaw) > max_head_yaw) {
 229                 float deviation = state.yaw < 0.0f ? state.yaw + max_head_yaw : state.yaw - max_head_yaw;
 230                 // rotate the entity by deviation about local Y
 231                 state.orient = rotate(state.orient, deviation, up);
 232                 // and remove from head yaw
 233                 state.yaw -= deviation;
 234                 // shouldn't be necessary if max_head_yaw is < PI, but just to be sure :p
 235                 state.AdjustHeading();
 236         }
 237         // update model if any
 238         if (model) {
 239                 model.EyesState().orientation = glm::quat(glm::vec3(state.pitch, state.yaw, 0.0f));
 240         }
 241 }
 242
 243
 244 EntityController::~EntityController() {
 245
 246 }
 247
 248 bool EntityController::MaxOutForce(
 249         glm::vec3 &out,
 250         const glm::vec3 &add,
 251         float max
 252 ) noexcept {
 253         if (iszero(add) || any(isnan(add))) {
 254                 return false;
 255         }
 256         float current = iszero(out) ? 0.0f : length(out);
 257         float remain = max - current;
 258         if (remain <= 0.0f) {
 259                 return true;
 260         }
 261         float additional = length(add);
 262         if (additional > remain) {
 263                 out += normalize(add) * remain;
 264                 return true;
 265         } else {
 266                 out += add;
 267                 return false;
 268         }
 269 }
 270
 271
 272 EntityState::EntityState()
 273 : pos()
 274 , velocity(0.0f)
 275 , orient(1.0f, 0.0f, 0.0f, 0.0f)
 276 , pitch(0.0f)
 277 , yaw(0.0f) {
 278
 279 }
 280
 281 void EntityState::AdjustPosition() noexcept {
 282         pos.Correct();
 283 }
 284
 285 void EntityState::AdjustHeading() noexcept {
 286         pitch = glm::clamp(pitch, -PI_0p5, PI_0p5);
 287         while (yaw > PI) {
 288                 yaw -= PI_2p0;
 289         }
 290         while (yaw < -PI) {
 291                 yaw += PI_2p0;
 292         }
 293 }
 294
 295 glm::mat4 EntityState::Transform(const glm::ivec3 &reference) const noexcept {
 296         const glm::vec3 translation = RelativePosition(reference);
 297         glm::mat4 transform(toMat4(orient));
 298         transform[3] = glm::vec4(translation, 1.0f);
 299         return transform;
 300 }
 301
 302
 303 Player::Player(Entity &e, ChunkIndex &c)
 304 : entity(e)
 305 , chunks(c)
 306 , inv_slot(0) {
 307
 308 }
 309
 310 Player::~Player() {
 311
 312 }
 313
 314 bool Player::SuitableSpawn(BlockLookup &spawn_block) const noexcept {
 315         if (!spawn_block || spawn_block.GetType().collide_block) {
 316                 return false;
 317         }
 318
 319         BlockLookup head_block(spawn_block.Next(Block::FACE_UP));
 320         if (!head_block || head_block.GetType().collide_block) {
 321                 return false;
 322         }
 323
 324         return true;
 325 }
 326
 327 void Player::Update(int dt) {
 328         chunks.Rebase(entity.ChunkCoords());
 329 }
 330
 331
 332 World::World(const BlockTypeRegistry &types, const Config &config)
 333 : config(config)
 334 , block_type(types)
 335 , chunks(types)
 336 , players()
 337 , entities()
 338 , light_direction(config.light_direction)
 339 , fog_density(config.fog_density) {
 340
 341 }
 342
 343 World::~World() {
 344         for (Entity &e : entities) {
 345                 e.Kill();
 346         }
 347         std::size_t removed = 0;
 348         do {
 349                 removed = 0;
 350                 for (auto e = entities.begin(), end = entities.end(); e != end; ++e) {
 351                         if (e->CanRemove()) {
 352                                 e = RemoveEntity(e);
 353                                 end = entities.end();
 354                                 ++removed;
 355                         }
 356                 }
 357         } while (removed > 0 && !entities.empty());
 358 }
 359
 360
 361 Player *World::AddPlayer(const std::string &name) {
 362         for (Player &p : players) {
 363                 if (p.Name() == name) {
 364                         return nullptr;
 365                 }
 366         }
 367         Entity &entity = AddEntity();
 368         entity.Name(name);
 369         entity.Bounds({ { -0.4f, -0.9f, -0.4f }, { 0.4f, 0.9f, 0.4f } });
 370         entity.WorldCollidable(true);
 371         ChunkIndex &index = chunks.MakeIndex(entity.ChunkCoords(), 6);
 372         players.emplace_back(entity, index);
 373         return &players.back();
 374 }
 375
 376 Player *World::AddPlayer(const std::string &name, std::uint32_t id) {
 377         for (Player &p : players) {
 378                 if (p.Name() == name) {
 379                         return nullptr;
 380                 }
 381         }
 382         Entity *entity = AddEntity(id);
 383         if (!entity) {
 384                 return nullptr;
 385         }
 386         entity->Name(name);
 387         entity->Bounds({ { -0.4f, -0.9f, -0.4f }, { 0.4f, 0.9f, 0.4f } });
 388         entity->WorldCollidable(true);
 389         ChunkIndex &index = chunks.MakeIndex(entity->ChunkCoords(), 6);
 390         players.emplace_back(*entity, index);
 391         return &players.back();
 392 }
 393
 394 Entity &World::AddEntity() {
 395         if (entities.empty()) {
 396                 entities.emplace_back();
 397                 entities.back().ID(1);
 398                 return entities.back();
 399         }
 400         if (entities.back().ID() < std::numeric_limits<std::uint32_t>::max()) {
 401                 std::uint32_t id = entities.back().ID() + 1;
 402                 entities.emplace_back();
 403                 entities.back().ID(id);
 404                 return entities.back();
 405         }
 406         std::uint32_t id = 1;
 407         auto position = entities.begin();
 408         auto end = entities.end();
 409         while (position != end && position->ID() == id) {
 410                 ++id;
 411                 ++position;
 412         }
 413         auto entity = entities.emplace(position);
 414         entity->ID(id);
 415         return *entity;
 416 }
 417
 418 Entity *World::AddEntity(std::uint32_t id) {
 419         if (entities.empty() || entities.back().ID() < id) {
 420                 entities.emplace_back();
 421                 entities.back().ID(id);
 422                 return &entities.back();
 423         }
 424
 425         auto position = entities.begin();
 426         auto end = entities.end();
 427         while (position != end && position->ID() < id) {
 428                 ++position;
 429         }
 430         if (position != end && position->ID() == id) {
 431                 return nullptr;
 432         }
 433         auto entity = entities.emplace(position);
 434         entity->ID(id);
 435         return &*entity;
 436 }
 437
 438 Entity &World::ForceAddEntity(std::uint32_t id) {
 439         if (entities.empty() || entities.back().ID() < id) {
 440                 entities.emplace_back();
 441                 entities.back().ID(id);
 442                 return entities.back();
 443         }
 444
 445         auto position = entities.begin();
 446         auto end = entities.end();
 447         while (position != end && position->ID() < id) {
 448                 ++position;
 449         }
 450         if (position != end && position->ID() == id) {
 451                 return *position;
 452         }
 453         auto entity = entities.emplace(position);
 454         entity->ID(id);
 455         return *entity;
 456 }
 457
 458
 459 namespace {
 460
 461 struct Candidate {
 462         Chunk *chunk;
 463         float dist;
 464 };
 465
 466 bool CandidateLess(const Candidate &a, const Candidate &b) {
 467         return a.dist < b.dist;
 468 }
 469
 470 std::vector<Candidate> candidates;
 471
 472 }
 473
 474 bool World::Intersection(
 475         const Ray &ray,
 476         const ExactLocation::Coarse &reference,
 477         WorldCollision &coll
 478 ) {
 479         candidates.clear();
 480
 481         for (Chunk &cur_chunk : chunks) {
 482                 float cur_dist;
 483                 if (cur_chunk.Intersection(ray, reference, cur_dist)) {
 484                         candidates.push_back({ &cur_chunk, cur_dist });
 485                 }
 486         }
 487
 488         if (candidates.empty()) return false;
 489
 490         std::sort(candidates.begin(), candidates.end(), CandidateLess);
 491
 492         coll.chunk = nullptr;
 493         coll.block = -1;
 494         coll.depth = std::numeric_limits<float>::infinity();
 495
 496         for (Candidate &cand : candidates) {
 497                 if (cand.dist > coll.depth) continue;
 498                 WorldCollision cur_coll;
 499                 if (cand.chunk->Intersection(ray, reference, cur_coll)) {
 500                         if (cur_coll.depth < coll.depth) {
 501                                 coll = cur_coll;
 502                         }
 503                 }
 504         }
 505
 506         return coll.chunk;
 507 }
 508
 509 bool World::Intersection(
 510         const Ray &ray,
 511         const Entity &reference,
 512         EntityCollision &coll
 513 ) {
 514         coll.entity = nullptr;
 515         coll.depth = std::numeric_limits<float>::infinity();
 516         for (Entity &cur_entity : entities) {
 517                 if (&cur_entity == &reference) {
 518                         continue;
 519                 }
 520                 float cur_dist;
 521                 glm::vec3 cur_normal;
 522                 if (blank::Intersection(ray, cur_entity.Bounds(), cur_entity.Transform(reference.ChunkCoords()), &cur_dist, &cur_normal)) {
 523                         // TODO: fine grained check goes here? maybe?
 524                         if (cur_dist < coll.depth) {
 525                                 coll.entity = &cur_entity;
 526                                 coll.depth = cur_dist;
 527                                 coll.normal = cur_normal;
 528                         }
 529                 }
 530         }
 531
 532         return coll.entity;
 533 }
 534
 535 bool World::Intersection(const Entity &e, const EntityState &s, std::vector<WorldCollision> &col) {
 536         // TODO: make special case for entities here and in Chunk::Intersection so entity's bounding radius
 537         //       doesn't have to be calculated over and over again (sqrt)
 538         glm::ivec3 reference = s.pos.chunk;
 539         glm::mat4 M = s.Transform(reference);
 540
 541         ExactLocation::Coarse begin(reference - 1);
 542         ExactLocation::Coarse end(reference + 2);
 543
 544         bool any = false;
 545         for (ExactLocation::Coarse pos(begin); pos.z < end.y; ++pos.z) {
 546                 for (pos.y = begin.y; pos.y < end.y; ++pos.y) {
 547                         for (pos.x = begin.x; pos.x < end.x; ++pos.x) {
 548                                 Chunk *chunk = chunks.Get(pos);
 549                                 if (chunk && chunk->Intersection(e, M, chunk->Transform(reference), col)) {
 550                                         any = true;
 551                                 }
 552                         }
 553                 }
 554         }
 555         return any;
 556 }
 557
 558 bool World::Intersection(
 559         const AABB &box,
 560         const glm::mat4 &M,
 561         const glm::ivec3 &reference,
 562         std::vector<WorldCollision> &col
 563 ) {
 564         bool any = false;
 565         for (Chunk &cur_chunk : chunks) {
 566                 if (manhattan_radius(cur_chunk.Position() - reference) > 1) {
 567                         // chunk is not one of the 3x3x3 surrounding the entity
 568                         // since there's no entity which can extent over 16 blocks, they can be skipped
 569                         continue;
 570                 }
 571                 if (cur_chunk.Intersection(box, M, cur_chunk.Transform(reference), col)) {
 572                         any = true;
 573                 }
 574         }
 575         return any;
 576 }
 577
 578 void World::Update(int dt) {
 579         float fdt(dt * 0.001f);
 580         for (Entity &entity : entities) {
 581                 Update(entity, fdt);
 582         }
 583         for (Entity &entity : entities) {
 584                 entity.Update(fdt);
 585         }
 586         for (Player &player : players) {
 587                 player.Update(dt);
 588         }
 589         for (auto iter = entities.begin(), end = entities.end(); iter != end;) {
 590                 if (iter->CanRemove()) {
 591                         iter = RemoveEntity(iter);
 592                 } else {
 593                         ++iter;
 594                 }
 595         }
 596 }
 597
 598 void World::Update(Entity &entity, float dt) {
 599         EntityState state(entity.GetState());
 600
 601         EntityDerivative a(CalculateStep(entity, state, 0.0f, EntityDerivative()));
 602         EntityDerivative b(CalculateStep(entity, state, dt * 0.5f, a));
 603         EntityDerivative c(CalculateStep(entity, state, dt * 0.5f, b));
 604         EntityDerivative d(CalculateStep(entity, state, dt, c));
 605
 606         EntityDerivative f;
 607         constexpr float sixth = 1.0f / 6.0f;
 608         f.position = sixth * (a.position + 2.0f * (b.position + c.position) + d.position);
 609         f.velocity = sixth * (a.velocity + 2.0f * (b.velocity + c.velocity) + d.velocity);
 610
 611         state.pos.block += f.position * dt;
 612         state.velocity += f.velocity * dt;
 613         CollisionFix(entity, state);
 614         state.AdjustPosition();
 615
 616         entity.SetState(state);
 617 }
 618
 619 EntityDerivative World::CalculateStep(
 620         const Entity &entity,
 621         const EntityState &cur,
 622         float dt,
 623         const EntityDerivative &delta
 624 ) {
 625         EntityState next(cur);
 626         next.pos.block += delta.position * dt;
 627         next.velocity += delta.velocity * dt;
 628         CollisionFix(entity, next);
 629         next.AdjustPosition();
 630
 631         if (dot(next.velocity, next.velocity) > entity.MaxVelocity() * entity.MaxVelocity()) {
 632                 next.velocity = normalize(next.velocity) * entity.MaxVelocity();
 633         }
 634
 635         EntityDerivative out;
 636         out.position = next.velocity;
 637         out.velocity = CalculateForce(entity, next); // by mass = 1kg
 638         return out;
 639 }
 640
 641 glm::vec3 World::CalculateForce(
 642         const Entity &entity,
 643         const EntityState &state
 644 ) {
 645         glm::vec3 force(ControlForce(entity, state));
 646         if (dot(force, force) > entity.MaxControlForce() * entity.MaxControlForce()) {
 647                 force = normalize(force) * entity.MaxControlForce();
 648         }
 649         return force + Gravity(entity, state);
 650 }
 651
 652 glm::vec3 World::ControlForce(
 653         const Entity &entity,
 654         const EntityState &state
 655 ) {
 656         return entity.ControlForce(state);
 657 }
 658
 659 namespace {
 660
 661 std::vector<WorldCollision> col;
 662
 663 }
 664
 665 void World::CollisionFix(
 666         const Entity &entity,
 667         EntityState &state
 668 ) {
 669         col.clear();
 670         if (!entity.WorldCollidable() || !Intersection(entity, state, col)) {
 671                 // no collision, no fix
 672                 return;
 673         }
 674         glm::vec3 correction = CombinedInterpenetration(state, col);
 675         // correction may be zero in which case normalize() returns NaNs
 676         if (iszero(correction)) {
 677                 return;
 678         }
 679         // if entity is already going in the direction of correction,
 680         // let the problem resolve itself
 681         if (dot(state.velocity, correction) >= 0.0f) {
 682                 return;
 683         }
 684         // apply correction, maybe could use some damping, gotta test
 685         state.pos.block += correction;
 686         // kill velocity?
 687         glm::vec3 normal_velocity(proj(state.velocity, correction));
 688         state.velocity -= normal_velocity;
 689         // apply force proportional to penetration
 690         // use velocity projected onto correction as damper
 691         //constexpr float k = 1000.0f; // spring constant
 692         //constexpr float b = 10.0f; // damper constant
 693         //const glm::vec3 x(-correction); // endpoint displacement from equilibrium in m
 694         //const glm::vec3 v(normal_velocity); // relative velocity between endpoints in m/s
 695         //return (((-k) * x) - (b * v)); // times 1kg/s, in kg*m/s²
 696 }
 697
 698 glm::vec3 World::CombinedInterpenetration(
 699         const EntityState &state,
 700         const std::vector<WorldCollision> &col
 701 ) noexcept {
 702         // determine displacement for each cardinal axis and move entity accordingly
 703         glm::vec3 min_pen(0.0f);
 704         glm::vec3 max_pen(0.0f);
 705         for (const WorldCollision &c : col) {
 706                 if (!c.Blocks()) continue;
 707                 glm::vec3 normal(c.normal);
 708                 // swap if neccessary (normal may point away from the entity)
 709                 if (dot(normal, state.RelativePosition(c.ChunkPos()) - c.BlockCoords()) < 0) {
 710                         normal = -normal;
 711                 }
 712                 // check if block surface is "inside"
 713                 Block::Face coll_face = Block::NormalFace(normal);
 714                 BlockLookup neighbor(c.chunk, c.BlockPos(), coll_face);
 715                 if (neighbor && neighbor.FaceFilled(Block::Opposite(coll_face))) {
 716                         // yep, so ignore this contact
 717                         continue;
 718                 }
 719                 glm::vec3 local_pen(normal * c.depth);
 720                 min_pen = min(min_pen, local_pen);
 721                 max_pen = max(max_pen, local_pen);
 722         }
 723         glm::vec3 pen(0.0f);
 724         // only apply correction for axes where penetration is only in one direction
 725         for (std::size_t i = 0; i < 3; ++i) {
 726                 if (min_pen[i] < -std::numeric_limits<float>::epsilon()) {
 727                         if (max_pen[i] < std::numeric_limits<float>::epsilon()) {
 728                                 pen[i] = min_pen[i];
 729                         }
 730                 } else {
 731                         pen[i] = max_pen[i];
 732                 }
 733         }
 734         return pen;
 735 }
 736
 737 glm::vec3 World::Gravity(
 738         const Entity &entity,
 739         const EntityState &state
 740 ) {
 741         glm::vec3 force(0.0f);
 742         ExactLocation::Coarse begin(state.pos.chunk - 1);
 743         ExactLocation::Coarse end(state.pos.chunk + 2);
 744
 745         for (ExactLocation::Coarse pos(begin); pos.z < end.z; ++pos.z) {
 746                 for (pos.y = begin.y; pos.y < end.y; ++pos.y) {
 747                         for (pos.x = begin.x; pos.x < end.x; ++pos.x) {
 748                                 Chunk *chunk = chunks.Get(pos);
 749                                 if (chunk) {
 750                                         force += chunk->GravityAt(state.pos);
 751                                 }
 752                         }
 753                 }
 754         }
 755
 756         return force;
 757 }
 758
 759 World::EntityHandle World::RemoveEntity(EntityHandle &eh) {
 760         // check for player
 761         for (auto player = players.begin(), end = players.end(); player != end;) {
 762                 if (&player->GetEntity() == &*eh) {
 763                         chunks.UnregisterIndex(player->GetChunks());
 764                         player = players.erase(player);
 765                         end = players.end();
 766                 } else {
 767                         ++player;
 768                 }
 769         }
 770         return entities.erase(eh);
 771 }
 772
 773
 774 void World::Render(Viewport &viewport) {
 775         DirectionalLighting &entity_prog = viewport.EntityProgram();
 776         entity_prog.SetFogDensity(fog_density);
 777
 778         glm::vec3 light_dir;
 779         glm::vec3 light_col;
 780         glm::vec3 ambient_col;
 781         for (Entity &entity : entities) {
 782                 glm::mat4 M(entity.Transform(players.front().GetEntity().ChunkCoords()));
 783                 if (!CullTest(entity.Bounds(), entity_prog.GetVP() * M)) {
 784                         GetLight(entity, light_dir, light_col, ambient_col);
 785                         entity_prog.SetLightDirection(light_dir);
 786                         entity_prog.SetLightColor(light_col);
 787                         entity_prog.SetAmbientColor(ambient_col);
 788                         entity.Render(M, entity_prog);
 789                 }
 790         }
 791 }
 792
 793 // this should interpolate based on the fractional part of entity's block position
 794 void World::GetLight(
 795         const Entity &e,
 796         glm::vec3 &dir,
 797         glm::vec3 &col,
 798         glm::vec3 &amb
 799 ) {
 800         Chunk *chunk = chunks.Get(e.ChunkCoords());
 801         if (!chunk) {
 802                 // chunk unavailable, so make it really dark and from
 803                 // some arbitrary direction
 804                 dir = glm::vec3(1.0f, 2.0f, 3.0f);
 805                 col = glm::vec3(0.025f); // ~0.8^15
 806                 return;
 807         }
 808         glm::ivec3 base(e.Position());
 809         int base_light = chunk->GetLight(base);
 810         int max_light = 0;
 811         int min_light = 15;
 812         glm::ivec3 acc(0, 0, 0);
 813         for (glm::ivec3 offset(-1, -1, -1); offset.z < 2; ++offset.z) {
 814                 for (offset.y = -1; offset.y < 2; ++offset.y) {
 815                         for (offset.x = -1; offset.x < 2; ++offset.x) {
 816                                 BlockLookup block(chunk, base + offset);
 817                                 if (!block) {
 818                                         // missing, just ignore it
 819                                         continue;
 820                                 }
 821                                 // otherwise, accumulate the difference times direction
 822                                 acc += offset * (base_light - block.GetLight());
 823                                 max_light = std::max(max_light, block.GetLight());
 824                                 min_light = std::min(min_light, block.GetLight());
 825                         }
 826                 }
 827         }
 828         dir = acc;
 829         col = glm::vec3(std::pow(0.8f, 15 - max_light));
 830         amb = glm::vec3(std::pow(0.8f, 15 - min_light));
 831 }
 832
 833 namespace {
 834
 835 PrimitiveMesh::Buffer debug_buf;
 836
 837 }
 838
 839 void World::RenderDebug(Viewport &viewport) {
 840         PrimitiveMesh debug_mesh;
 841         PlainColor &prog = viewport.WorldColorProgram();
 842         for (const Entity &entity : entities) {
 843                 debug_buf.OutlineBox(entity.Bounds(), glm::vec4(1.0f, 0.0f, 0.0f, 1.0f));
 844                 debug_mesh.Update(debug_buf);
 845                 prog.SetM(entity.Transform(players.front().GetEntity().ChunkCoords()));
 846                 debug_mesh.DrawLines();
 847         }
 848 }
 849
 850 }