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