]> git.localhorst.tv Git - blank.git/blobdiff - src/world/world.cpp
indexed iteration in ray/world collision tests
[blank.git] / src / world / world.cpp
index d2b05d66850e96923704bfd262335af5cc464832..243fb8a81b439655193b21615a84eddc7b70c389 100644 (file)
@@ -1,4 +1,5 @@
 #include "Entity.hpp"
+#include "EntityCollision.hpp"
 #include "EntityController.hpp"
 #include "EntityDerivative.hpp"
 #include "EntityState.hpp"
@@ -11,6 +12,7 @@
 #include "../app/Assets.hpp"
 #include "../geometry/const.hpp"
 #include "../geometry/distance.hpp"
+#include "../geometry/rotation.hpp"
 #include "../graphics/Format.hpp"
 #include "../graphics/Viewport.hpp"
 
 
 namespace blank {
 
+namespace {
+
+/// used as a buffer for merging collisions
+std::vector<WorldCollision> col;
+
+}
+
 Entity::Entity() noexcept
-: ctrl(nullptr)
+: steering(*this)
+, ctrl(nullptr)
 , model()
 , id(-1)
 , name("anonymous")
@@ -51,7 +61,8 @@ Entity::~Entity() noexcept {
 }
 
 Entity::Entity(const Entity &other) noexcept
-: ctrl(other.ctrl)
+: steering(*this)
+, ctrl(other.ctrl)
 , model(other.model)
 , id(-1)
 , name(other.name)
@@ -90,11 +101,7 @@ void Entity::UnsetController() noexcept {
 }
 
 glm::vec3 Entity::ControlForce(const EntityState &s) const noexcept {
-       if (HasController()) {
-               return GetController().ControlForce(*this, s);
-       } else {
-               return -s.velocity;
-       }
+       return steering.Force(s);
 }
 
 void Entity::Position(const glm::ivec3 &c, const glm::vec3 &b) noexcept {
@@ -129,15 +136,58 @@ Ray Entity::Aim(const ExactLocation::Coarse &chunk_offset) const noexcept {
        return Ray{ glm::vec3(transform[3]), -glm::vec3(transform[2]) };
 }
 
-void Entity::Update(float dt) {
-       UpdateTransforms();
-       UpdateHeading();
+void Entity::Update(World &world, float dt) {
        if (HasController()) {
                GetController().Update(*this, dt);
        }
+       steering.Update(world, dt);
+       UpdatePhysics(world, dt);
+       UpdateTransforms();
+       UpdateHeading();
        UpdateModel(dt);
 }
 
+void Entity::UpdatePhysics(World &world, float dt) {
+       EntityState s(state);
+
+       EntityDerivative a(CalculateStep(world, s, 0.0f, EntityDerivative()));
+       EntityDerivative b(CalculateStep(world, s, dt * 0.5f, a));
+       EntityDerivative c(CalculateStep(world, s, dt * 0.5f, b));
+       EntityDerivative d(CalculateStep(world, s, dt, c));
+
+       EntityDerivative f;
+       constexpr float sixth = 1.0f / 6.0f;
+       f.position = sixth * (a.position + 2.0f * (b.position + c.position) + d.position);
+       f.velocity = sixth * (a.velocity + 2.0f * (b.velocity + c.velocity) + d.velocity);
+
+       s.pos.block += f.position * dt;
+       s.velocity += f.velocity * dt;
+       limit(s.velocity, max_vel);
+       world.ResolveWorldCollision(*this, s);
+       s.AdjustPosition();
+
+       SetState(s);
+}
+
+EntityDerivative Entity::CalculateStep(
+       World &world,
+       const EntityState &cur,
+       float dt,
+       const EntityDerivative &delta
+) const {
+       EntityState next(cur);
+       next.pos.block += delta.position * dt;
+       next.velocity += delta.velocity * dt;
+       limit(next.velocity, max_vel);
+       next.AdjustPosition();
+
+       EntityDerivative out;
+       out.position = next.velocity;
+       out.velocity = ControlForce(next) + world.GravityAt(next.pos); // by mass = 1kg
+       return out;
+}
+
+
 void Entity::UpdateTransforms() noexcept {
        // model transform is the one given by current state
        model_transform = state.Transform(state.pos.chunk);
@@ -210,7 +260,7 @@ void Entity::OrientBody(float dt) noexcept {
                                std::cout << "direction: " << direction << std::endl;
                                std::cout << "difference: " << glm::degrees(relative_difference) << "°" << std::endl;
                                std::cout << "correction: " << glm::degrees(correction) << "°" << std::endl;
-                               std::cout  << std::endl;
+                               std::cout << std::endl;
                        }
                        // now rotate body by correction and head by -correction
                        state.orient = rotate(state.orient, correction, up);
@@ -241,31 +291,46 @@ void Entity::OrientHead(float dt) noexcept {
 }
 
 
-EntityController::~EntityController() {
+EntityCollision::EntityCollision(Entity *e, float d, const glm::vec3 &n)
+: depth(d)
+, normal(n)
+, entity(e) {
+       if (entity) {
+               entity->Ref();
+       }
+}
 
+EntityCollision::~EntityCollision() {
+       if (entity) {
+               entity->UnRef();
+       }
 }
 
-bool EntityController::MaxOutForce(
-       glm::vec3 &out,
-       const glm::vec3 &add,
-       float max
-) noexcept {
-       if (iszero(add) || any(isnan(add))) {
-               return false;
+EntityCollision::EntityCollision(const EntityCollision &other)
+: depth(other.depth)
+, normal(other.normal)
+, entity(other.entity) {
+       if (entity) {
+               entity->Ref();
        }
-       float current = iszero(out) ? 0.0f : length(out);
-       float remain = max - current;
-       if (remain <= 0.0f) {
-               return true;
+}
+
+EntityCollision &EntityCollision::operator =(const EntityCollision &other) {
+       if (entity) {
+               entity->UnRef();
        }
-       float additional = length(add);
-       if (additional > remain) {
-               out += normalize(add) * remain;
-               return true;
-       } else {
-               out += add;
-               return false;
+       depth = other.depth;
+       normal = other.normal;
+       entity = other.entity;
+       if (entity) {
+               entity->Ref();
        }
+       return *this;
+}
+
+
+EntityController::~EntityController() {
+
 }
 
 
@@ -329,15 +394,253 @@ void Player::Update(int dt) {
 }
 
 
+Steering::Steering(const Entity &e)
+: entity(e)
+, target_entity(nullptr)
+, target_velocity(0.0f)
+, accel(1.0f)
+, speed(entity.MaxVelocity())
+, wander_radius(1.0f)
+, wander_dist(2.0f)
+, wander_disp(1.0f)
+, wander_pos(1.0f, 0.0f, 0.0f)
+, obstacle_dir(0.0f)
+, enabled(0) {
+
+}
+
+Steering::~Steering() {
+       ClearTargetEntity();
+}
+
+Steering &Steering::SetTargetEntity(Entity &e) noexcept {
+       ClearTargetEntity();
+       target_entity = &e;
+       e.Ref();
+       return *this;
+}
+
+Steering &Steering::ClearTargetEntity() noexcept {
+       if (target_entity) {
+               target_entity->UnRef();
+               target_entity = nullptr;
+       }
+       return *this;
+}
+
+void Steering::Update(World &world, float dt) {
+       if (AnyEnabled(WANDER)) {
+               UpdateWander(world, dt);
+       }
+       if (AnyEnabled(OBSTACLE_AVOIDANCE)) {
+               UpdateObstacle(world);
+       }
+}
+
+void Steering::UpdateWander(World &world, float dt) {
+       glm::vec3 displacement(
+               world.Random().SNorm() * wander_disp,
+               world.Random().SNorm() * wander_disp,
+               world.Random().SNorm() * wander_disp
+       );
+       if (!iszero(displacement)) {
+               wander_pos = normalize(wander_pos + displacement * dt) * wander_radius;
+       }
+}
+
+void Steering::UpdateObstacle(World &world) {
+       if (!entity.Moving()) {
+               obstacle_dir = glm::vec3(0.0f);
+               return;
+       }
+       AABB box(entity.Bounds());
+       box.min.z = -entity.Speed();
+       box.max.z = 0.0f;
+       glm::mat4 transform(find_rotation(glm::vec3(0.0f, 0.0f, -1.0f), entity.Heading()));
+       transform[3] = glm::vec4(entity.Position(), 1.0f);
+       // check if that box intersects with any blocks
+       col.clear();
+       if (!world.Intersection(box, transform, entity.ChunkCoords(), col)) {
+               obstacle_dir = glm::vec3(0.0f);
+               return;
+       }
+       // if so, pick the nearest collision
+       const WorldCollision *nearest = nullptr;
+       glm::vec3 difference(0.0f);
+       float distance = std::numeric_limits<float>::infinity();
+       for (const WorldCollision &c : col) {
+               // diff points from block to state
+               glm::vec3 diff = entity.GetState().RelativePosition(c.ChunkPos()) - c.BlockCoords();
+               float dist = length2(diff);
+               if (dist < distance) {
+                       nearest = &c;
+                       difference = diff;
+                       distance = dist;
+               }
+       }
+       if (!nearest) {
+               // intersection test lied to us
+               obstacle_dir = glm::vec3(0.0f);
+               return;
+       }
+       // and try to avoid it
+       float to_go = dot(difference, entity.Heading());
+       glm::vec3 point(entity.Position() + entity.Heading() * to_go);
+       obstacle_dir = normalize(point - nearest->BlockCoords()) * (entity.Speed() / std::sqrt(distance));
+}
+
+glm::vec3 Steering::Force(const EntityState &state) const noexcept {
+       glm::vec3 force(0.0f);
+       if (!enabled) {
+               return force;
+       }
+       const float max = entity.MaxControlForce();
+       if (AnyEnabled(HALT)) {
+               if (SumForce(force, Halt(state), max)) {
+                       return force;
+               }
+       }
+       if (AnyEnabled(TARGET_VELOCITY)) {
+               if (SumForce(force, TargetVelocity(state, target_velocity), max)) {
+                       return force;
+               }
+       }
+       if (AnyEnabled(OBSTACLE_AVOIDANCE)) {
+               if (SumForce(force, ObstacleAvoidance(state), max)) {
+                       return force;
+               }
+       }
+       if (AnyEnabled(EVADE_TARGET)) {
+               if (HasTargetEntity()) {
+                       if (SumForce(force, Evade(state, GetTargetEntity()), max)) {
+                               return force;
+                       }
+               } else {
+                       std::cout << "Steering: evade enabled, but target entity not set" << std::endl;
+               }
+       }
+       if (AnyEnabled(PURSUE_TARGET)) {
+               if (HasTargetEntity()) {
+                       if (SumForce(force, Pursuit(state, GetTargetEntity()), max)) {
+                               return force;
+                       }
+               } else {
+                       std::cout << "Steering: pursuit enabled, but target entity not set" << std::endl;
+               }
+       }
+       if (AnyEnabled(WANDER)) {
+               if (SumForce(force, Wander(state), max)) {
+                       return force;
+               }
+       }
+       return force;
+}
+
+bool Steering::SumForce(glm::vec3 &out, const glm::vec3 &in, float max) noexcept {
+       if (iszero(in) || any(isnan(in))) {
+               return false;
+       }
+       float current = iszero(out) ? 0.0f : length(out);
+       float remain = max - current;
+       if (remain <= 0.0f) {
+               return true;
+       }
+       float additional = length(in);
+       if (additional > remain) {
+               out += normalize(in) * remain;
+               return true;
+       } else {
+               out += in;
+               return false;
+       }
+}
+
+glm::vec3 Steering::Halt(const EntityState &state) const noexcept {
+       return state.velocity * -accel;
+}
+
+glm::vec3 Steering::TargetVelocity(const EntityState &state, const glm::vec3 &vel) const noexcept {
+       return (vel - state.velocity) * accel;
+}
+
+glm::vec3 Steering::Seek(const EntityState &state, const ExactLocation &loc) const noexcept {
+       const glm::vec3 diff(loc.Difference(state.pos).Absolute());
+       if (iszero(diff)) {
+               return glm::vec3(0.0f);
+       } else {
+               return TargetVelocity(state, normalize(diff) * speed);
+       }
+}
+
+glm::vec3 Steering::Flee(const EntityState &state, const ExactLocation &loc) const noexcept {
+       const glm::vec3 diff(state.pos.Difference(loc).Absolute());
+       if (iszero(diff)) {
+               return glm::vec3(0.0f);
+       } else {
+               return TargetVelocity(state, normalize(diff) * speed);
+       }
+}
+
+glm::vec3 Steering::Arrive(const EntityState &state, const ExactLocation &loc) const noexcept {
+       const glm::vec3 diff(loc.Difference(state.pos).Absolute());
+       const float dist = length(diff);
+       if (dist < std::numeric_limits<float>::epsilon()) {
+               return glm::vec3(0.0f);
+       } else {
+               const float att_speed = std::min(dist * accel, speed);
+               return TargetVelocity(state, diff * att_speed / dist);
+       }
+}
+
+glm::vec3 Steering::Pursuit(const EntityState &state, const Entity &other) const noexcept {
+       const glm::vec3 diff(state.Diff(other.GetState()));
+       if (iszero(diff)) {
+               return TargetVelocity(state, other.Velocity());
+       } else {
+               const float time_estimate = length(diff) / speed;
+               ExactLocation prediction(other.ChunkCoords(), other.Position() + (other.Velocity() * time_estimate));
+               return Seek(state, prediction);
+       }
+}
+
+glm::vec3 Steering::Evade(const EntityState &state, const Entity &other) const noexcept {
+       const glm::vec3 diff(state.Diff(other.GetState()));
+       if (iszero(diff)) {
+               return TargetVelocity(state, -other.Velocity());
+       } else {
+               const float time_estimate = length(diff) / speed;
+               ExactLocation prediction(other.ChunkCoords(), other.Position() + (other.Velocity() * time_estimate));
+               return Flee(state, prediction);
+       }
+}
+
+glm::vec3 Steering::Wander(const EntityState &state) const noexcept {
+       return TargetVelocity(state, normalize(entity.Heading() * wander_dist + wander_pos) * speed);
+}
+
+glm::vec3 Steering::ObstacleAvoidance(const EntityState &state) const noexcept {
+       return obstacle_dir;
+}
+
+
 World::World(const BlockTypeRegistry &types, const Config &config)
 : config(config)
 , block_type(types)
 , chunks(types)
 , players()
 , entities()
+, rng(
+#ifdef BLANK_PROFILING
+0
+#else
+std::time(nullptr)
+#endif
+)
 , light_direction(config.light_direction)
 , fog_density(config.fog_density) {
-
+       for (int i = 0; i < 4; ++i) {
+               rng.Next<int>();
+       }
 }
 
 World::~World() {
@@ -476,12 +779,22 @@ bool World::Intersection(
        const ExactLocation::Coarse &reference,
        WorldCollision &coll
 ) {
+       // only consider chunks of the idex closest to reference
+       // this makes the ray not be infinite anymore (which means it's
+       // actually a line segment), but oh well
+       ChunkIndex *index = chunks.ClosestIndex(reference);
+       if (!index) {
+               return false;
+       }
+
        candidates.clear();
 
-       for (Chunk &cur_chunk : chunks) {
+       // TODO: convert to coords based iteration and trim based
+       //       on ray direction
+       for (Chunk *cur_chunk : *index) {
                float cur_dist;
-               if (cur_chunk.Intersection(ray, reference, cur_dist)) {
-                       candidates.push_back({ &cur_chunk, cur_dist });
+               if (cur_chunk && cur_chunk->Intersection(ray, reference, cur_dist)) {
+                       candidates.push_back({ cur_chunk, cur_dist });
                }
        }
 
@@ -511,8 +824,7 @@ bool World::Intersection(
        const Entity &reference,
        EntityCollision &coll
 ) {
-       coll.entity = nullptr;
-       coll.depth = std::numeric_limits<float>::infinity();
+       coll = EntityCollision(nullptr, std::numeric_limits<float>::infinity(), glm::vec3(0.0f));
        for (Entity &cur_entity : entities) {
                if (&cur_entity == &reference) {
                        continue;
@@ -522,19 +834,15 @@ bool World::Intersection(
                if (blank::Intersection(ray, cur_entity.Bounds(), cur_entity.Transform(reference.ChunkCoords()), &cur_dist, &cur_normal)) {
                        // TODO: fine grained check goes here? maybe?
                        if (cur_dist < coll.depth) {
-                               coll.entity = &cur_entity;
-                               coll.depth = cur_dist;
-                               coll.normal = cur_normal;
+                               coll = EntityCollision(&cur_entity, cur_dist, cur_normal);
                        }
                }
        }
 
-       return coll.entity;
+       return coll;
 }
 
 bool World::Intersection(const Entity &e, const EntityState &s, std::vector<WorldCollision> &col) {
-       // TODO: make special case for entities here and in Chunk::Intersection so entity's bounding radius
-       //       doesn't have to be calculated over and over again (sqrt)
        glm::ivec3 reference = s.pos.chunk;
        glm::mat4 M = s.Transform(reference);
 
@@ -542,7 +850,7 @@ bool World::Intersection(const Entity &e, const EntityState &s, std::vector<Worl
        ExactLocation::Coarse end(reference + 2);
 
        bool any = false;
-       for (ExactLocation::Coarse pos(begin); pos.z < end.y; ++pos.z) {
+       for (ExactLocation::Coarse pos(begin); pos.z < end.z; ++pos.z) {
                for (pos.y = begin.y; pos.y < end.y; ++pos.y) {
                        for (pos.x = begin.x; pos.x < end.x; ++pos.x) {
                                Chunk *chunk = chunks.Get(pos);
@@ -561,15 +869,19 @@ bool World::Intersection(
        const glm::ivec3 &reference,
        std::vector<WorldCollision> &col
 ) {
+       // this only works if box's diameter is < than 16
+       ExactLocation::Coarse begin(reference - 1);
+       ExactLocation::Coarse end(reference + 2);
+
        bool any = false;
-       for (Chunk &cur_chunk : chunks) {
-               if (manhattan_radius(cur_chunk.Position() - reference) > 1) {
-                       // chunk is not one of the 3x3x3 surrounding the entity
-                       // since there's no entity which can extent over 16 blocks, they can be skipped
-                       continue;
-               }
-               if (cur_chunk.Intersection(box, M, cur_chunk.Transform(reference), col)) {
-                       any = true;
+       for (ExactLocation::Coarse pos(begin); pos.z < end.z; ++pos.z) {
+               for (pos.y = begin.y; pos.y < end.y; ++pos.y) {
+                       for (pos.x = begin.x; pos.x < end.x; ++pos.x) {
+                               Chunk *chunk = chunks.Get(pos);
+                               if (chunk && chunk->Intersection(box, M, chunk->Transform(reference), col)) {
+                                       any = true;
+                               }
+                       }
                }
        }
        return any;
@@ -578,10 +890,7 @@ bool World::Intersection(
 void World::Update(int dt) {
        float fdt(dt * 0.001f);
        for (Entity &entity : entities) {
-               Update(entity, fdt);
-       }
-       for (Entity &entity : entities) {
-               entity.Update(fdt);
+               entity.Update(*this, fdt);
        }
        for (Player &player : players) {
                player.Update(dt);
@@ -595,99 +904,30 @@ void World::Update(int dt) {
        }
 }
 
-void World::Update(Entity &entity, float dt) {
-       EntityState state(entity.GetState());
-
-       EntityDerivative a(CalculateStep(entity, state, 0.0f, EntityDerivative()));
-       EntityDerivative b(CalculateStep(entity, state, dt * 0.5f, a));
-       EntityDerivative c(CalculateStep(entity, state, dt * 0.5f, b));
-       EntityDerivative d(CalculateStep(entity, state, dt, c));
-
-       EntityDerivative f;
-       constexpr float sixth = 1.0f / 6.0f;
-       f.position = sixth * (a.position + 2.0f * (b.position + c.position) + d.position);
-       f.velocity = sixth * (a.velocity + 2.0f * (b.velocity + c.velocity) + d.velocity);
-
-       state.pos.block += f.position * dt;
-       state.velocity += f.velocity * dt;
-       state.AdjustPosition();
-
-       entity.SetState(state);
-}
-
-EntityDerivative World::CalculateStep(
+void World::ResolveWorldCollision(
        const Entity &entity,
-       const EntityState &cur,
-       float dt,
-       const EntityDerivative &delta
+       EntityState &state
 ) {
-       EntityState next(cur);
-       next.pos.block += delta.position * dt;
-       next.velocity += delta.velocity * dt;
-       next.AdjustPosition();
-
-       if (dot(next.velocity, next.velocity) > entity.MaxVelocity() * entity.MaxVelocity()) {
-               next.velocity = normalize(next.velocity) * entity.MaxVelocity();
+       col.clear();
+       if (!entity.WorldCollidable() || !Intersection(entity, state, col)) {
+               // no collision, no fix
+               return;
        }
-
-       EntityDerivative out;
-       out.position = next.velocity;
-       out.velocity = CalculateForce(entity, next); // by mass = 1kg
-       return out;
-}
-
-glm::vec3 World::CalculateForce(
-       const Entity &entity,
-       const EntityState &state
-) {
-       glm::vec3 force(ControlForce(entity, state) + CollisionForce(entity, state) + Gravity(entity, state));
-       if (dot(force, force) > entity.MaxControlForce() * entity.MaxControlForce()) {
-               return normalize(force) * entity.MaxControlForce();
-       } else {
-               return force;
+       glm::vec3 correction = CombinedInterpenetration(state, col);
+       // correction may be zero in which case normalize() returns NaNs
+       if (iszero(correction)) {
+               return;
        }
-}
-
-glm::vec3 World::ControlForce(
-       const Entity &entity,
-       const EntityState &state
-) {
-       return entity.ControlForce(state);
-}
-
-namespace {
-
-std::vector<WorldCollision> col;
-
-}
-
-glm::vec3 World::CollisionForce(
-       const Entity &entity,
-       const EntityState &state
-) {
-       col.clear();
-       if (entity.WorldCollidable() && Intersection(entity, state, col)) {
-               glm::vec3 correction = -CombinedInterpenetration(state, col);
-               // correction may be zero in which case normalize() returns NaNs
-               if (iszero(correction)) {
-                       return glm::vec3(0.0f);
-               }
-               // if entity is already going in the direction of correction,
-               // let the problem resolve itself
-               if (dot(state.velocity, correction) >= 0.0f) {
-                       return glm::vec3(0.0f);
-               }
-               glm::vec3 normal_velocity(proj(state.velocity, correction));
-               // apply force proportional to penetration
-               // use velocity projected onto correction as damper
-               constexpr float k = 1000.0f; // spring constant
-               constexpr float b = 10.0f; // damper constant
-               const glm::vec3 x(-correction); // endpoint displacement from equilibrium in m
-               const glm::vec3 v(normal_velocity); // relative velocity between endpoints in m/s
-               return (((-k) * x) - (b * v)); // times 1kg/s, in kg*m/s²
-       } else {
-               return glm::vec3(0.0f);
+       // if entity is already going in the direction of correction,
+       // let the problem resolve itself
+       if (dot(state.velocity, correction) >= 0.0f) {
+               return;
        }
+       // apply correction, maybe could use some damping, gotta test
+       state.pos.block += correction;
+       // kill velocity?
+       glm::vec3 normal_velocity(proj(state.velocity, correction));
+       state.velocity -= normal_velocity;
 }
 
 glm::vec3 World::CombinedInterpenetration(
@@ -699,11 +939,19 @@ glm::vec3 World::CombinedInterpenetration(
        glm::vec3 max_pen(0.0f);
        for (const WorldCollision &c : col) {
                if (!c.Blocks()) continue;
-               glm::vec3 local_pen(c.normal * c.depth);
+               glm::vec3 normal(c.normal);
                // swap if neccessary (normal may point away from the entity)
-               if (dot(c.normal, state.RelativePosition(c.ChunkPos()) - c.BlockCoords()) > 0) {
-                       local_pen *= -1;
+               if (dot(normal, state.RelativePosition(c.ChunkPos()) - c.BlockCoords()) < 0) {
+                       normal = -normal;
+               }
+               // check if block surface is "inside"
+               Block::Face coll_face = Block::NormalFace(normal);
+               BlockLookup neighbor(c.chunk, c.BlockPos(), coll_face);
+               if (neighbor && neighbor.FaceFilled(Block::Opposite(coll_face))) {
+                       // yep, so ignore this contact
+                       continue;
                }
+               glm::vec3 local_pen(normal * c.depth);
                min_pen = min(min_pen, local_pen);
                max_pen = max(max_pen, local_pen);
        }
@@ -721,20 +969,17 @@ glm::vec3 World::CombinedInterpenetration(
        return pen;
 }
 
-glm::vec3 World::Gravity(
-       const Entity &entity,
-       const EntityState &state
-) {
+glm::vec3 World::GravityAt(const ExactLocation &loc) const noexcept {
        glm::vec3 force(0.0f);
-       ExactLocation::Coarse begin(state.pos.chunk - 1);
-       ExactLocation::Coarse end(state.pos.chunk + 2);
+       ExactLocation::Coarse begin(loc.chunk - 1);
+       ExactLocation::Coarse end(loc.chunk + 2);
 
        for (ExactLocation::Coarse pos(begin); pos.z < end.z; ++pos.z) {
                for (pos.y = begin.y; pos.y < end.y; ++pos.y) {
                        for (pos.x = begin.x; pos.x < end.x; ++pos.x) {
-                               Chunk *chunk = chunks.Get(pos);
+                               const Chunk *chunk = chunks.Get(pos);
                                if (chunk) {
-                                       force += chunk->GravityAt(state.pos);
+                                       force += chunk->GravityAt(loc);
                                }
                        }
                }
@@ -784,23 +1029,23 @@ void World::GetLight(
        glm::vec3 &col,
        glm::vec3 &amb
 ) {
-       Chunk *chunk = chunks.Get(e.ChunkCoords());
-       if (!chunk) {
+       BlockLookup center(chunks.Get(e.ChunkCoords()), e.Position());
+       if (!center) {
                // chunk unavailable, so make it really dark and from
                // some arbitrary direction
                dir = glm::vec3(1.0f, 2.0f, 3.0f);
                col = glm::vec3(0.025f); // ~0.8^15
                return;
        }
-       glm::ivec3 base(e.Position());
-       int base_light = chunk->GetLight(base);
+       glm::ivec3 base(center.GetBlockPos());
+       int base_light = center.GetLight();
        int max_light = 0;
        int min_light = 15;
        glm::ivec3 acc(0, 0, 0);
        for (glm::ivec3 offset(-1, -1, -1); offset.z < 2; ++offset.z) {
                for (offset.y = -1; offset.y < 2; ++offset.y) {
                        for (offset.x = -1; offset.x < 2; ++offset.x) {
-                               BlockLookup block(chunk, base + offset);
+                               BlockLookup block(&center.GetChunk(), center.GetBlockPos() + offset);
                                if (!block) {
                                        // missing, just ignore it
                                        continue;