]> git.localhorst.tv Git - blank.git/blobdiff - src/world/world.cpp
some annotations
[blank.git] / src / world / world.cpp
index e77192b277b46c8a592c9049f00601c59be1a08f..d2b05d66850e96923704bfd262335af5cc464832 100644 (file)
@@ -9,6 +9,8 @@
 #include "EntityCollision.hpp"
 #include "WorldCollision.hpp"
 #include "../app/Assets.hpp"
+#include "../geometry/const.hpp"
+#include "../geometry/distance.hpp"
 #include "../graphics/Format.hpp"
 #include "../graphics/Viewport.hpp"
 
 #include <cmath>
 #include <iostream>
 #include <limits>
+#include <glm/gtx/euler_angles.hpp>
 #include <glm/gtx/io.hpp>
+#include <glm/gtx/projection.hpp>
 #include <glm/gtx/quaternion.hpp>
+#include <glm/gtx/rotate_vector.hpp>
 #include <glm/gtx/transform.hpp>
 
 
@@ -29,7 +34,9 @@ Entity::Entity() noexcept
 , id(-1)
 , name("anonymous")
 , bounds()
+, radius(0.0f)
 , state()
+, heading(0.0f, 0.0f, -1.0f)
 , max_vel(5.0f)
 , max_force(25.0f)
 , ref_count(0)
@@ -50,6 +57,10 @@ Entity::Entity(const Entity &other) noexcept
 , name(other.name)
 , bounds(other.bounds)
 , state(other.state)
+, model_transform(1.0f)
+, view_transform(1.0f)
+, speed(0.0f)
+, heading(0.0f, 0.0f, -1.0f)
 , max_vel(other.max_vel)
 , max_force(other.max_force)
 , ref_count(0)
@@ -80,19 +91,19 @@ void Entity::UnsetController() noexcept {
 
 glm::vec3 Entity::ControlForce(const EntityState &s) const noexcept {
        if (HasController()) {
-               return GetController().ControlForce(s);
+               return GetController().ControlForce(*this, s);
        } else {
                return -s.velocity;
        }
 }
 
 void Entity::Position(const glm::ivec3 &c, const glm::vec3 &b) noexcept {
-       state.chunk_pos = c;
-       state.block_pos = b;
+       state.pos.chunk = c;
+       state.pos.block = b;
 }
 
 void Entity::Position(const glm::vec3 &pos) noexcept {
-       state.block_pos = pos;
+       state.pos.block = pos;
        state.AdjustPosition();
 }
 
@@ -103,48 +114,129 @@ void Entity::TurnHead(float dp, float dy) noexcept {
 void Entity::SetHead(float p, float y) noexcept {
        state.pitch = p;
        state.yaw = y;
-       // TODO: I feel like this could be delayed
-       UpdateModel();
 }
 
 glm::mat4 Entity::Transform(const glm::ivec3 &reference) const noexcept {
-       return state.Transform(reference);
+       return glm::translate(glm::vec3((state.pos.chunk - reference) * ExactLocation::Extent())) * model_transform;
 }
 
 glm::mat4 Entity::ViewTransform(const glm::ivec3 &reference) const noexcept {
-       glm::mat4 transform = Transform(reference);
+       return Transform(reference) * view_transform;
+}
+
+Ray Entity::Aim(const ExactLocation::Coarse &chunk_offset) const noexcept {
+       glm::mat4 transform = ViewTransform(chunk_offset);
+       return Ray{ glm::vec3(transform[3]), -glm::vec3(transform[2]) };
+}
+
+void Entity::Update(float dt) {
+       UpdateTransforms();
+       UpdateHeading();
+       if (HasController()) {
+               GetController().Update(*this, dt);
+       }
+       UpdateModel(dt);
+}
+
+void Entity::UpdateTransforms() noexcept {
+       // model transform is the one given by current state
+       model_transform = state.Transform(state.pos.chunk);
+       // view transform is either the model's eyes transform or,
+       // should the entity have no model, the pitch (yaw already is
+       // in model transform)
        if (model) {
-               transform *= model.EyesTransform();
+               view_transform = model.EyesTransform();
+       } else {
+               view_transform = toMat4(glm::quat(glm::vec3(state.pitch, state.yaw, 0.0f)));
        }
-       return transform;
 }
 
-Ray Entity::Aim(const Chunk::Pos &chunk_offset) const noexcept {
-       glm::mat4 transform = ViewTransform(chunk_offset);
-       glm::vec4 from = transform * glm::vec4(0.0f, 0.0f, 0.0f, 1.0f);
-       from /= from.w;
-       glm::vec4 to = transform * glm::vec4(0.0f, 0.0f, -1.0f, 1.0f);
-       to /= to.w;
-       return Ray{ glm::vec3(from), glm::normalize(glm::vec3(to - from)) };
+void Entity::UpdateHeading() noexcept {
+       speed = length(Velocity());
+       if (speed > std::numeric_limits<float>::epsilon()) {
+               heading = Velocity() / speed;
+       } else {
+               speed = 0.0f;
+               // use -Z (forward axis) of model transform (our "chest")
+               heading = -glm::vec3(model_transform[2]);
+       }
 }
 
-void Entity::UpdateModel() noexcept {
+void Entity::UpdateModel(float dt) noexcept {
+       // first, sanitize the pitch and yaw fields of state (our input)
+       // those indicate the head orientation in the entity's local cosystem
        state.AdjustHeading();
-       if (model) {
-               Part::State &body_state = model.BodyState();
-               Part::State &eyes_state = model.EyesState();
-               if (&body_state != &eyes_state) {
-                       body_state.orientation = glm::quat(glm::vec3(0.0f, state.yaw, 0.0f));
-                       eyes_state.orientation = glm::quat(glm::vec3(state.pitch, 0.0f, 0.0f));
-               } else {
-                       eyes_state.orientation = glm::quat(glm::vec3(state.pitch, state.yaw, 0.0f));
+       // TODO: this flickers horrible and also shouldn't be based on velocity, but on control force
+       //OrientBody(dt);
+       OrientHead(dt);
+}
+
+void Entity::OrientBody(float dt) noexcept {
+       // maximum body rotation per second (due to velocity orientation) (90°)
+       constexpr float max_body_turn_per_second = PI_0p5;
+       const float max_body_turn = max_body_turn_per_second * dt;
+       // minimum speed to apply body correction
+       constexpr float min_speed = 0.0625f;
+       // use local Y as up
+       const glm::vec3 up(model_transform[1]);
+       if (speed > min_speed) {
+               // check if our orientation and velocity are aligned
+               const glm::vec3 forward(-model_transform[2]);
+               // facing is local -Z rotated about local Y by yaw and transformed into world space
+               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))));
+               // only adjust if velocity isn't almost parallel to up
+               float vel_dot_up = dot(Velocity(), up);
+               if (std::abs(1.0f - std::abs(vel_dot_up)) > std::numeric_limits<float>::epsilon()) {
+                       // get direction of velocity projected onto model plane
+                       glm::vec3 direction(normalize(Velocity() - (Velocity() * vel_dot_up)));
+                       // if velocity points away from our facing (with a little bias), flip it around
+                       // (the entity is "walking backwards")
+                       if (dot(facing, direction) < -0.1f) {
+                               direction = -direction;
+                       }
+                       // calculate the difference between forward and direction
+                       const float absolute_difference = std::acos(dot(forward, direction));
+                       // if direction is clockwise with respect to up vector, invert the angle
+                       const float relative_difference = dot(cross(forward, direction), up) < 0.0f
+                               ? -absolute_difference
+                               : absolute_difference;
+                       // only correct by half the difference max
+                       const float correction = glm::clamp(relative_difference * 0.5f, -max_body_turn, max_body_turn);
+                       if (ID() == 1) {
+                               std::cout << "orientation before: " << state.orient << std::endl;
+                               std::cout << "up:        " << up << std::endl;
+                               std::cout << "forward:   " << forward << std::endl;
+                               std::cout << "facing:    " << facing << std::endl;
+                               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;
+                       }
+                       // now rotate body by correction and head by -correction
+                       state.orient = rotate(state.orient, correction, up);
+                       state.yaw -= correction;
                }
        }
 }
 
-void Entity::Update(float dt) {
-       if (HasController()) {
-               GetController().Update(*this, dt);
+void Entity::OrientHead(float dt) noexcept {
+       // maximum yaw of head (60°)
+       constexpr float max_head_yaw = PI / 3.0f;
+       // use local Y as up
+       const glm::vec3 up(model_transform[1]);
+       // if yaw is bigger than max, rotate the body to accomodate
+       if (std::abs(state.yaw) > max_head_yaw) {
+               float deviation = state.yaw < 0.0f ? state.yaw + max_head_yaw : state.yaw - max_head_yaw;
+               // rotate the entity by deviation about local Y
+               state.orient = rotate(state.orient, deviation, up);
+               // and remove from head yaw
+               state.yaw -= deviation;
+               // shouldn't be necessary if max_head_yaw is < PI, but just to be sure :p
+               state.AdjustHeading();
+       }
+       // update model if any
+       if (model) {
+               model.EyesState().orientation = glm::quat(glm::vec3(state.pitch, state.yaw, 0.0f));
        }
 }
 
@@ -153,10 +245,32 @@ EntityController::~EntityController() {
 
 }
 
+bool EntityController::MaxOutForce(
+       glm::vec3 &out,
+       const glm::vec3 &add,
+       float max
+) noexcept {
+       if (iszero(add) || any(isnan(add))) {
+               return false;
+       }
+       float current = iszero(out) ? 0.0f : length(out);
+       float remain = max - current;
+       if (remain <= 0.0f) {
+               return true;
+       }
+       float additional = length(add);
+       if (additional > remain) {
+               out += normalize(add) * remain;
+               return true;
+       } else {
+               out += add;
+               return false;
+       }
+}
+
 
 EntityState::EntityState()
-: chunk_pos(0)
-, block_pos(0.0f)
+: pos()
 , velocity(0.0f)
 , orient(1.0f, 0.0f, 0.0f, 0.0f)
 , pitch(0.0f)
@@ -165,53 +279,23 @@ EntityState::EntityState()
 }
 
 void EntityState::AdjustPosition() noexcept {
-       while (block_pos.x >= Chunk::width) {
-               block_pos.x -= Chunk::width;
-               ++chunk_pos.x;
-       }
-       while (block_pos.x < 0) {
-               block_pos.x += Chunk::width;
-               --chunk_pos.x;
-       }
-       while (block_pos.y >= Chunk::height) {
-               block_pos.y -= Chunk::height;
-               ++chunk_pos.y;
-       }
-       while (block_pos.y < 0) {
-               block_pos.y += Chunk::height;
-               --chunk_pos.y;
-       }
-       while (block_pos.z >= Chunk::depth) {
-               block_pos.z -= Chunk::depth;
-               ++chunk_pos.z;
-       }
-       while (block_pos.z < 0) {
-               block_pos.z += Chunk::depth;
-               --chunk_pos.z;
-       }
+       pos.Correct();
 }
 
 void EntityState::AdjustHeading() noexcept {
-       while (pitch > PI / 2) {
-               pitch = PI / 2;
-       }
-       while (pitch < -PI / 2) {
-               pitch = -PI / 2;
-       }
+       pitch = glm::clamp(pitch, -PI_0p5, PI_0p5);
        while (yaw > PI) {
-               yaw -= PI * 2;
+               yaw -= PI_2p0;
        }
        while (yaw < -PI) {
-               yaw += PI * 2;
+               yaw += PI_2p0;
        }
 }
 
 glm::mat4 EntityState::Transform(const glm::ivec3 &reference) const noexcept {
        const glm::vec3 translation = RelativePosition(reference);
        glm::mat4 transform(toMat4(orient));
-       transform[3].x = translation.x;
-       transform[3].y = translation.y;
-       transform[3].z = translation.z;
+       transform[3] = glm::vec4(translation, 1.0f);
        return transform;
 }
 
@@ -257,7 +341,20 @@ World::World(const BlockTypeRegistry &types, const Config &config)
 }
 
 World::~World() {
-
+       for (Entity &e : entities) {
+               e.Kill();
+       }
+       std::size_t removed = 0;
+       do {
+               removed = 0;
+               for (auto e = entities.begin(), end = entities.end(); e != end; ++e) {
+                       if (e->CanRemove()) {
+                               e = RemoveEntity(e);
+                               end = entities.end();
+                               ++removed;
+                       }
+               }
+       } while (removed > 0 && !entities.empty());
 }
 
 
@@ -376,15 +473,14 @@ std::vector<Candidate> candidates;
 
 bool World::Intersection(
        const Ray &ray,
-       const glm::mat4 &M,
-       const Chunk::Pos &reference,
+       const ExactLocation::Coarse &reference,
        WorldCollision &coll
 ) {
        candidates.clear();
 
        for (Chunk &cur_chunk : chunks) {
                float cur_dist;
-               if (cur_chunk.Intersection(ray, M * cur_chunk.Transform(reference), cur_dist)) {
+               if (cur_chunk.Intersection(ray, reference, cur_dist)) {
                        candidates.push_back({ &cur_chunk, cur_dist });
                }
        }
@@ -400,7 +496,7 @@ bool World::Intersection(
        for (Candidate &cand : candidates) {
                if (cand.dist > coll.depth) continue;
                WorldCollision cur_coll;
-               if (cand.chunk->Intersection(ray, M * cand.chunk->Transform(reference), cur_coll)) {
+               if (cand.chunk->Intersection(ray, reference, cur_coll)) {
                        if (cur_coll.depth < coll.depth) {
                                coll = cur_coll;
                        }
@@ -412,7 +508,6 @@ bool World::Intersection(
 
 bool World::Intersection(
        const Ray &ray,
-       const glm::mat4 &M,
        const Entity &reference,
        EntityCollision &coll
 ) {
@@ -424,7 +519,7 @@ bool World::Intersection(
                }
                float cur_dist;
                glm::vec3 cur_normal;
-               if (blank::Intersection(ray, cur_entity.Bounds(), M * cur_entity.Transform(reference.ChunkCoords()), &cur_dist, &cur_normal)) {
+               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;
@@ -438,9 +533,34 @@ bool World::Intersection(
 }
 
 bool World::Intersection(const Entity &e, const EntityState &s, std::vector<WorldCollision> &col) {
-       AABB box = e.Bounds();
-       Chunk::Pos reference = s.chunk_pos;
+       // 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);
+
+       ExactLocation::Coarse begin(reference - 1);
+       ExactLocation::Coarse end(reference + 2);
+
+       bool any = false;
+       for (ExactLocation::Coarse pos(begin); pos.z < end.y; ++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(e, M, chunk->Transform(reference), col)) {
+                                       any = true;
+                               }
+                       }
+               }
+       }
+       return any;
+}
+
+bool World::Intersection(
+       const AABB &box,
+       const glm::mat4 &M,
+       const glm::ivec3 &reference,
+       std::vector<WorldCollision> &col
+) {
        bool any = false;
        for (Chunk &cur_chunk : chunks) {
                if (manhattan_radius(cur_chunk.Position() - reference) > 1) {
@@ -455,14 +575,13 @@ bool World::Intersection(const Entity &e, const EntityState &s, std::vector<Worl
        return any;
 }
 
-
 void World::Update(int dt) {
        float fdt(dt * 0.001f);
        for (Entity &entity : entities) {
-               entity.Update(fdt);
+               Update(entity, fdt);
        }
        for (Entity &entity : entities) {
-               Update(entity, fdt);
+               entity.Update(fdt);
        }
        for (Player &player : players) {
                player.Update(dt);
@@ -486,10 +605,10 @@ void World::Update(Entity &entity, float dt) {
 
        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);
+       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.block_pos += f.position * dt;
+       state.pos.block += f.position * dt;
        state.velocity += f.velocity * dt;
        state.AdjustPosition();
 
@@ -503,10 +622,14 @@ EntityDerivative World::CalculateStep(
        const EntityDerivative &delta
 ) {
        EntityState next(cur);
-       next.block_pos += delta.position * dt;
+       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();
+       }
+
        EntityDerivative out;
        out.position = next.velocity;
        out.velocity = CalculateForce(entity, next); // by mass = 1kg
@@ -517,7 +640,12 @@ glm::vec3 World::CalculateForce(
        const Entity &entity,
        const EntityState &state
 ) {
-       return ControlForce(entity, state) + CollisionForce(entity, state) + Gravity(entity, 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 World::ControlForce(
@@ -539,38 +667,19 @@ glm::vec3 World::CollisionForce(
 ) {
        col.clear();
        if (entity.WorldCollidable() && Intersection(entity, state, col)) {
-               // determine displacement for each cardinal axis and move entity accordingly
-               glm::vec3 min_pen(0.0f);
-               glm::vec3 max_pen(0.0f);
-               for (const WorldCollision &c : col) {
-                       if (!c.Blocks()) continue;
-                       glm::vec3 local_pen(c.normal * c.depth);
-                       // swap if neccessary (normal may point away from the entity)
-                       if (dot(c.normal, state.RelativePosition(c.ChunkPos()) - c.BlockCoords()) > 0) {
-                               local_pen *= -1;
-                       }
-                       min_pen = min(min_pen, local_pen);
-                       max_pen = max(max_pen, local_pen);
-               }
-               glm::vec3 correction(0.0f);
-               // only apply correction for axes where penetration is only in one direction
-               for (std::size_t i = 0; i < 3; ++i) {
-                       if (min_pen[i] < -std::numeric_limits<float>::epsilon()) {
-                               if (max_pen[i] < std::numeric_limits<float>::epsilon()) {
-                                       correction[i] = -min_pen[i];
-                               }
-                       } else {
-                               correction[i] = -max_pen[i];
-                       }
-               }
+               glm::vec3 correction = -CombinedInterpenetration(state, col);
                // correction may be zero in which case normalize() returns NaNs
-               if (dot(correction, correction) < std::numeric_limits<float>::epsilon()) {
+               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(normalize(correction));
-               glm::vec3 normal_velocity(normal * dot(state.velocity, normal));
+               glm::vec3 normal_velocity(proj(state.velocity, correction));
                // apply force proportional to penetration
-               // use velocity projected onto normal as damper
+               // 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
@@ -581,11 +690,57 @@ glm::vec3 World::CollisionForce(
        }
 }
 
+glm::vec3 World::CombinedInterpenetration(
+       const EntityState &state,
+       const std::vector<WorldCollision> &col
+) noexcept {
+       // determine displacement for each cardinal axis and move entity accordingly
+       glm::vec3 min_pen(0.0f);
+       glm::vec3 max_pen(0.0f);
+       for (const WorldCollision &c : col) {
+               if (!c.Blocks()) continue;
+               glm::vec3 local_pen(c.normal * c.depth);
+               // swap if neccessary (normal may point away from the entity)
+               if (dot(c.normal, state.RelativePosition(c.ChunkPos()) - c.BlockCoords()) > 0) {
+                       local_pen *= -1;
+               }
+               min_pen = min(min_pen, local_pen);
+               max_pen = max(max_pen, local_pen);
+       }
+       glm::vec3 pen(0.0f);
+       // only apply correction for axes where penetration is only in one direction
+       for (std::size_t i = 0; i < 3; ++i) {
+               if (min_pen[i] < -std::numeric_limits<float>::epsilon()) {
+                       if (max_pen[i] < std::numeric_limits<float>::epsilon()) {
+                               pen[i] = min_pen[i];
+                       }
+               } else {
+                       pen[i] = max_pen[i];
+               }
+       }
+       return pen;
+}
+
 glm::vec3 World::Gravity(
        const Entity &entity,
        const EntityState &state
 ) {
-       return glm::vec3(0.0f);
+       glm::vec3 force(0.0f);
+       ExactLocation::Coarse begin(state.pos.chunk - 1);
+       ExactLocation::Coarse end(state.pos.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);
+                               if (chunk) {
+                                       force += chunk->GravityAt(state.pos);
+                               }
+                       }
+               }
+       }
+
+       return force;
 }
 
 World::EntityHandle World::RemoveEntity(EntityHandle &eh) {
@@ -605,11 +760,77 @@ World::EntityHandle World::RemoveEntity(EntityHandle &eh) {
 
 void World::Render(Viewport &viewport) {
        DirectionalLighting &entity_prog = viewport.EntityProgram();
-       entity_prog.SetLightDirection(light_direction);
        entity_prog.SetFogDensity(fog_density);
 
+       glm::vec3 light_dir;
+       glm::vec3 light_col;
+       glm::vec3 ambient_col;
        for (Entity &entity : entities) {
-               entity.Render(entity.Transform(players.front().GetEntity().ChunkCoords()), entity_prog);
+               glm::mat4 M(entity.Transform(players.front().GetEntity().ChunkCoords()));
+               if (!CullTest(entity.Bounds(), entity_prog.GetVP() * M)) {
+                       GetLight(entity, light_dir, light_col, ambient_col);
+                       entity_prog.SetLightDirection(light_dir);
+                       entity_prog.SetLightColor(light_col);
+                       entity_prog.SetAmbientColor(ambient_col);
+                       entity.Render(M, entity_prog);
+               }
+       }
+}
+
+// this should interpolate based on the fractional part of entity's block position
+void World::GetLight(
+       const Entity &e,
+       glm::vec3 &dir,
+       glm::vec3 &col,
+       glm::vec3 &amb
+) {
+       Chunk *chunk = chunks.Get(e.ChunkCoords());
+       if (!chunk) {
+               // 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);
+       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);
+                               if (!block) {
+                                       // missing, just ignore it
+                                       continue;
+                               }
+                               // otherwise, accumulate the difference times direction
+                               acc += offset * (base_light - block.GetLight());
+                               max_light = std::max(max_light, block.GetLight());
+                               min_light = std::min(min_light, block.GetLight());
+                       }
+               }
+       }
+       dir = acc;
+       col = glm::vec3(std::pow(0.8f, 15 - max_light));
+       amb = glm::vec3(std::pow(0.8f, 15 - min_light));
+}
+
+namespace {
+
+PrimitiveMesh::Buffer debug_buf;
+
+}
+
+void World::RenderDebug(Viewport &viewport) {
+       PrimitiveMesh debug_mesh;
+       PlainColor &prog = viewport.WorldColorProgram();
+       for (const Entity &entity : entities) {
+               debug_buf.OutlineBox(entity.Bounds(), glm::vec4(1.0f, 0.0f, 0.0f, 1.0f));
+               debug_mesh.Update(debug_buf);
+               prog.SetM(entity.Transform(players.front().GetEntity().ChunkCoords()));
+               debug_mesh.DrawLines();
        }
 }