4 files changed, 676 insertions, 0 deletions
diff --git a/src/shared/movement/movement.cc b/src/shared/movement/movement.cc
new file mode 100644
index 0000000..53d7a23
--- /dev/null
+++ b/src/shared/movement/movement.cc
@@ -0,0 +1,580 @@
+#include "shared/movement/movement.hh"
+
+namespace shared {
+namespace movement {
+
+constexpr float MAX_SPEED_XZ = 5.0f;         // max speed before sprinting
+constexpr float MAX_SPEED_XZ_LIQUID = 2.8f;  // max water speed before sprinting
+constexpr float MAX_SPEED_XZ_FLYING = 11.0f; // max water speed before sprinting
+constexpr float MAX_SPEED_Y = 80.0f;
+constexpr float MAX_SPEED_Y_LIQUID = 3.0f;
+constexpr float MAX_SPEED_Y_FLYING = 8.0f;
+constexpr float MOVE_ACCEL = 75.0f;  // base acceleration in m*s^-2
+constexpr float AIR_MULT = 0.125f;   // multiplier to acceleration if in air
+constexpr float SPRINT_MULT = 1.20f; // multiplier to acceleration if sprinting
+constexpr float SWIM_ACCEL = 50.0f;  // y-axis accel when swimming in m*s^-2
+constexpr float JUMP_ACCEL = 7.85f;  // y-axis accel when jumping in m*s^-2
+constexpr float FLY_ACCEL = 75.0f;   // y-axis accel when swimming in m*s^-2
+
+constexpr float GRAVITY = 28.0f;
+constexpr float DRAG = 0.1f;
+constexpr float FRICTION = 15.0f;
+constexpr float FLY_DRAG = FRICTION;
+constexpr float VISCOSITY = 25.0f;
+
+glm::vec3 make_relative(const shared::math::coords& base_chunk_pos,
+                        const glm::vec3& other_local_pos,
+                        const shared::math::coords& other_chunk_pos) noexcept {
+    const auto diff_x = static_cast<std::int64_t>(other_chunk_pos.x) -
+                        static_cast<std::int64_t>(base_chunk_pos.x);
+    const auto diff_z = static_cast<std::int64_t>(other_chunk_pos.z) -
+                        static_cast<std::int64_t>(base_chunk_pos.z);
+    return {
+        other_local_pos.x + static_cast<float>(world::chunk::WIDTH * diff_x),
+        other_local_pos.y,
+        other_local_pos.z + static_cast<float>(world::chunk::WIDTH * diff_z)};
+}
+
+void normalise_position(glm::vec3& local_pos,
+                        shared::math::coords& chunk_pos) noexcept {
+    const bool g_x = (local_pos.x >= world::chunk::WIDTH);
+    const bool l_x = (local_pos.x < 0.0f);
+    const bool g_z = (local_pos.z >= world::chunk::WIDTH);
+    const bool l_z = (local_pos.z < 0.0f);
+
+    chunk_pos.x += g_x - l_x;
+    local_pos.x += shared::world::chunk::WIDTH * (l_x - g_x);
+    chunk_pos.z += g_z - l_z;
+    local_pos.z += shared::world::chunk::WIDTH * (l_z - g_z);
+}
+
+glm::ivec2 get_move_xy(const std::uint32_t& tickrate,
+                       const shared::moveable& moveable) noexcept {
+    const float max_x = std::max(
+        MAX_SPEED_XZ, std::max(MAX_SPEED_XZ_LIQUID, MAX_SPEED_XZ_FLYING));
+    const float max_y =
+        std::max(MAX_SPEED_Y, std::max(MAX_SPEED_Y_LIQUID, MAX_SPEED_Y_FLYING));
+    const float mult = 1.0f / static_cast<float>(tickrate);
+    const auto& aabb = moveable.get_aabb();
+    return {max_x * mult + aabb.max.x + 1.0f, max_y * mult + aabb.max.y + 1.0f};
+}
+
+static float get_block_friction(const enum world::block::type block) noexcept {
+    if (world::block::is_liquid(block)) {
+        return VISCOSITY;
+    }
+    if (world::block::is_collidable(block)) {
+        return FRICTION;
+    }
+    return DRAG;
+}
+
+bool intersect_aabbs(const aabb& a, const aabb& b) noexcept {
+    if (a.max.x < b.min.x || a.min.x > b.max.x) {
+        return false;
+    }
+    if (a.max.y < b.min.y || a.min.y > b.max.y) {
+        return false;
+    }
+    if (a.max.z < b.min.z || a.min.z > b.max.z) {
+        return false;
+    }
+    return true;
+}
+
+static glm::vec3 plane_to_normal(const int plane) noexcept {
+    glm::vec3 normal{0.0f, 0.0f, 0.0f};
+    normal[std::abs(plane) - 1] = std::signbit(plane) ? -1.0f : 1.0f;
+    return normal;
+}
+
+std::optional<ray_aabb_ret> intersect_ray_aabb(const line& line,
+                                               const aabb& aabb) noexcept {
+    float tmin = -std::numeric_limits<float>::max();
+    float tmax = std::numeric_limits<float>::max();
+
+    int p = 0;
+    for (int i = 0; i < 3; ++i) {
+        if (std::abs(line.dir[i]) < EPSILON) {
+
+            // Ray is parallel to slab, no hit if origin not within slab.
+            if (line.origin[i] < aabb.min[i] || line.origin[i] > aabb.max[i]) {
+                return std::nullopt;
+            }
+
+        } else {
+            // Intersection t value of ray with near and far plane of slab.
+            const float ood = 1.0f / line.dir[i];
+            float t1 = (aabb.min[i] - line.origin[i]) * ood;
+            float t2 = (aabb.max[i] - line.origin[i]) * ood;
+
+            if (t1 > t2) {
+                std::swap(t1, t2);
+            }
+            auto old = tmin;
+            tmin = std::max(tmin, t1);
+            if (tmin != old) {
+                p = (i + 1);
+            }
+            tmax = std::min(tmax, t2);
+            if (tmin > tmax) {
+                return std::nullopt;
+            }
+        }
+    }
+
+    if (tmin <= 0.0f) {
+        return std::nullopt;
+    }
+
+    return ray_aabb_ret{.position = line.origin + line.dir * tmin,
+                        .time = tmin,
+                        .normal = plane_to_normal(p)};
+}
+
+std::optional<moving_aabb_ret>
+intersect_moving_aabbs(const moving_aabb& a, const moving_aabb& b) noexcept {
+
+    if (intersect_aabbs(a.aabb, b.aabb)) {
+        return std::nullopt;
+    }
+
+    const glm::vec3 velocity = b.velocity - a.velocity;
+    float tfirst = 0.0f;
+    float tlast = 10.0f;
+    int p = 0;
+
+    for (int i = 0; i < 3; ++i) {
+        if (velocity[i] < 0.0f) {
+            if (b.aabb.max[i] < a.aabb.min[i]) {
+                return std::nullopt;
+            }
+            if (a.aabb.max[i] < b.aabb.min[i]) {
+                const auto old = tfirst;
+                tfirst = std::max((a.aabb.max[i] - b.aabb.min[i]) / velocity[i],
+                                  tfirst);
+                if (tfirst != old) {
+                    p = (i + 1);
+                }
+            }
+            if (b.aabb.max[i] > a.aabb.min[i]) {
+                tlast = std::min((a.aabb.min[i] - b.aabb.max[i]) / velocity[i],
+                                 tlast);
+            }
+        } else if (velocity[i] > 0.0f) {
+            if (b.aabb.min[i] > a.aabb.max[i]) {
+                return std::nullopt;
+            }
+            if (b.aabb.max[i] < a.aabb.min[i]) {
+                const auto old = tfirst;
+                tfirst = std::max((a.aabb.min[i] - b.aabb.max[i]) / velocity[i],
+                                  tfirst);
+                if (tfirst != old) {
+                    p = -(i + 1);
+                }
+            }
+            if (a.aabb.max[i] > b.aabb.min[i]) {
+                tlast = std::min((a.aabb.max[i] - b.aabb.min[i]) / velocity[i],
+                                 tlast);
+            }
+        } else {
+            if (b.aabb.max[i] < a.aabb.min[i] ||
+                b.aabb.min[i] > a.aabb.max[i]) {
+                return std::nullopt;
+            }
+        }
+        if (tfirst > tlast) {
+            return std::nullopt;
+        }
+    }
+
+    return moving_aabb_ret{.time = tfirst, .normal = plane_to_normal(p)};
+}
+
+// Gets the closest collision of an entity to a block.
+struct collide_ret {
+    moving_aabb_ret collision;
+    shared::world::block block;
+};
+static std::optional<collide_ret> collide(const aabb& aabb,
+                                          const blocks& blocks,
+                                          const glm::vec3& move) noexcept {
+
+    const moving_aabb moving_aabb{.aabb = aabb, .velocity = move};
+
+    // TODO: It's possible we collide at the same time, but on a different block
+    // If this occurs, we will phase through it as we ignore the other
+    // collision. So fix it by doing some maths.
+    std::optional<collide_ret> collision;
+    for (const auto& block_aabb : blocks) {
+        if (!shared::world::block::is_collidable(block_aabb.block)) {
+            continue;
+        }
+
+        const struct moving_aabb block_moving_aabb {
+            .aabb = block_aabb.aabb, .velocity = { 0.0f, 0.0f, 0.0f }
+        };
+        const auto intersect =
+            intersect_moving_aabbs(moving_aabb, block_moving_aabb);
+
+        if (!intersect.has_value() || intersect->time >= 1.0f) {
+            continue;
+        }
+
+        // Update collision if it doesn't exist or if this one is closer.
+        if (!collision.has_value() ||
+            intersect->time < collision->collision.time) {
+
+            collision =
+                collide_ret{.collision = *intersect, .block = block_aabb.block};
+        }
+    }
+
+    return collision;
+}
+
+// Returns the closest ground object if such an object exists.
+static std::optional<shared::world::block>
+maybe_get_ground(const blocks& blocks, const aabb& aabb,
+                 bool (*filter)(const enum shared::world::block::type) =
+                     world::block::is_tangible) noexcept {
+    const moving_aabb moving_aabb{.aabb = aabb,
+                                  .velocity = {0.0f, -1.0f, 0.0f}};
+
+    // blockinfo, cur max distance
+    std::optional<std::pair<block, float>> ground;
+    for (const auto& block : blocks) {
+
+        if (!filter(block.block)) {
+            continue;
+        }
+
+        const struct moving_aabb block_moving_aabb {
+            .aabb = block.aabb, .velocity = { 0.0f, 0.0f, 0.0f }
+        };
+
+        if (const auto intersect =
+                intersect_moving_aabbs(moving_aabb, block_moving_aabb);
+            intersect.has_value()) {
+
+            if (intersect->time > EPSILON2) {
+                continue;
+            }
+
+            const float distance =
+                glm::distance(aabb.min, block.aabb.min); // cool hack
+
+            if (!ground.has_value()) {
+                ground.emplace(std::make_pair(block, distance));
+                continue;
+            }
+
+            const auto& [cur_max_block, cur_max_distance] = *ground;
+            if (distance >= cur_max_distance) {
+                continue;
+            }
+
+            ground.emplace(std::make_pair(block, distance));
+        }
+    }
+    if (ground.has_value()) {
+        return ground->first.block;
+    }
+    return std::nullopt;
+}
+
+static bool is_intersecting(
+    const blocks& blocks, const aabb& aabb,
+    bool (*filter)(const enum shared::world::block::type)) noexcept {
+    for (const auto& block_aabb : blocks) {
+        if (!filter(block_aabb.block)) {
+            continue;
+        }
+        if (!intersect_aabbs(block_aabb.aabb, aabb)) {
+            continue;
+        }
+        return true;
+    }
+    return false;
+}
+
+struct vectors {
+    glm::vec3 up;
+    glm::vec3 front;
+    glm::vec3 right;
+};
+
+static glm::vec3 get_accel(const blocks& blocks, const aabb& aabb,
+                           const vectors& vectors,
+                           const entity::index_t& commands) noexcept {
+    glm::vec3 acceleration{};
+
+    const auto add_input = [&](const auto& mask, const glm::vec3& dir) {
+        if (commands & mask) {
+            acceleration += dir;
+        }
+    };
+    add_input(animate::mask::forward, vectors.front);
+    add_input(animate::mask::left, -vectors.right);
+    add_input(animate::mask::backward, -vectors.front);
+    add_input(animate::mask::right, vectors.right);
+
+    acceleration.y = 0.0f; // so we don't move faster when facing up/down
+    if (acceleration != glm::vec3{}) {
+        acceleration = glm::normalize(acceleration);
+    }
+    acceleration *= MOVE_ACCEL; // 7.25 blocks/sec^2 by default
+    if (commands & animate::mask::sprint) {
+        acceleration *= SPRINT_MULT;
+    }
+
+    const bool in_water =
+        is_intersecting(blocks, aabb, world::block::is_liquid);
+
+    if ((commands & animate::mask::jump) && in_water) {
+        acceleration += SWIM_ACCEL * vectors.up;
+    }
+
+    // flying up/down
+    if (commands & animate::mask::flying) {
+        if (commands & animate::mask::jump) {
+            acceleration += FLY_ACCEL * vectors.up;
+        }
+        if (commands & animate::mask::crouch) {
+            acceleration -= FLY_ACCEL * vectors.up;
+        }
+    }
+
+    const bool on_ground =
+        maybe_get_ground(blocks, aabb, world::block::is_collidable).has_value();
+    // Move slower in the air, also our hitbox must be outside non-tangible.
+    if (!on_ground && !in_water && !(commands & animate::mask::flying)) {
+        acceleration *= AIR_MULT;
+    }
+
+    // gravity - only applied if there isn't a collidable block beneath us.
+    // or if we're not flying
+    if (!on_ground && !(commands & animate::mask::flying)) {
+        acceleration -= GRAVITY * vectors.up;
+    }
+
+    return acceleration;
+}
+
+static float get_decel_factor(const blocks& blocks, const aabb& aabb,
+                              const entity::index_t& commands) noexcept {
+
+    const float drag = [&]() -> float { // max drag of all intersecting blocks
+        float max = 0.0f;
+        for (const auto& block : blocks) {
+            if (!intersect_aabbs(aabb, block.aabb)) {
+                continue;
+            }
+            max = std::max(max, get_block_friction(block.block));
+        }
+
+        if (commands & animate::flying) {
+            return std::max(max, FLY_DRAG);
+        }
+
+        return max;
+    }();
+
+    const float friction = [&]() -> float {
+        const auto ground =
+            maybe_get_ground(blocks, aabb, world::block::is_collidable);
+        return ground.has_value() ? get_block_friction(*ground) : 0.0f;
+    }();
+
+    // Our deceleration is simply the max of what we're in and what we're on
+    return std::max(drag, friction);
+}
+
+static void decelerate(glm::vec3& velocity, const blocks& blocks,
+                       const aabb& aabb, const entity::index_t& commands,
+                       const float max_time) noexcept {
+    const float decel =
+        get_decel_factor(blocks, aabb, commands) * max_time * 2.0f;
+
+    if (const float xy_speed = glm::length(glm::vec2{velocity.x, velocity.z});
+        xy_speed > 0.0f) {
+
+        const float new_speed = std::max(0.0f, xy_speed - decel);
+        velocity.x *= new_speed / xy_speed;
+        velocity.z *= new_speed / xy_speed;
+    }
+
+    // we decelerate on y, but only if we're flying
+    if (const float y_speed = std::abs(velocity.y);
+        y_speed > 0.0f && (commands & shared::animate::flying)) {
+
+        velocity.y *= std::max(0.0f, y_speed - decel) / y_speed;
+    }
+}
+
+static void clamp_move_xy(float& x, float& z, const entity::index_t& commands,
+                          const bool in_liquid,
+                          const float mult = 1.0f) noexcept {
+
+    const float max_speed_xy = [&]() {
+        const float base = [&]() { // lol
+            if (commands & animate::mask::flying) {
+                return MAX_SPEED_XZ_FLYING;
+            }
+            if (in_liquid) {
+                return MAX_SPEED_XZ_LIQUID;
+            }
+            return MAX_SPEED_XZ;
+        }();
+        if (commands & animate::mask::sprint) {
+            return base * SPRINT_MULT;
+        }
+        return base;
+    }() * mult;
+
+    if (const float speed_xz = std::hypot(x, z); speed_xz > max_speed_xy) {
+        const float ratio = max_speed_xy / speed_xz;
+        x *= ratio;
+        z *= ratio;
+    }
+}
+
+static void clamp_move_y(float& y, const entity::index_t& commands,
+                         const bool in_liquid,
+                         const float mult = 1.0f) noexcept {
+    const float max_speed_y = [&]() {
+        if (commands & animate::mask::flying) {
+            return MAX_SPEED_Y_FLYING;
+        }
+        return in_liquid ? MAX_SPEED_Y_LIQUID : MAX_SPEED_Y;
+    }() * mult;
+
+    if (const float speed_y = std::abs(y); speed_y > max_speed_y) {
+        const float ratio = max_speed_y / speed_y;
+        y *= ratio;
+    }
+}
+
+static void clamp_move(glm::vec3& move, const entity::index_t& commands,
+                       const bool in_liquid, const float mult = 1.0f) noexcept {
+
+    clamp_move_xy(move.x, move.z, commands, in_liquid, mult);
+    clamp_move_y(move.y, commands, in_liquid, mult);
+}
+
+static void handle_jumps(glm::vec3& velocity, const blocks& blocks,
+                         const aabb& aabb, const entity::index_t& commands,
+                         const bool in_liquid) noexcept {
+    if (!(commands & animate::mask::jump)) {
+        return;
+    }
+    if (!(velocity.y >= 0 && velocity.y <= EPSILON)) {
+        return;
+    }
+    if (in_liquid) {
+        return;
+    }
+    if (!maybe_get_ground(blocks, aabb, world::block::is_collidable)) {
+        return;
+    }
+    // TODO: the jump will only occur in the next movement tick
+    // fix this by modifying both our velocity and our move vector
+    velocity.y += JUMP_ACCEL;
+}
+
+static void handle_collisions(glm::vec3& velocity, glm::vec3& local_pos,
+                              glm::vec3 move, const blocks& blocks, aabb aabb,
+                              const entity::index_t& commands,
+                              const float max_time) noexcept {
+    constexpr int MAX_COLLISIONS = 100;
+    for (int collisions = 0; collisions < MAX_COLLISIONS; ++collisions) {
+
+        {
+            const bool in_liquid =
+                is_intersecting(blocks, aabb, world::block::is_liquid);
+
+            handle_jumps(velocity, blocks, aabb, commands, in_liquid);
+            clamp_move(velocity, commands, in_liquid);
+            clamp_move(move, commands, in_liquid, max_time);
+        }
+
+        const auto collision = collide(aabb, blocks, move);
+
+        if (!collision.has_value()) {
+            local_pos += move;
+            return;
+        }
+
+        const glm::vec3 pos = move * collision->collision.time;
+        const glm::vec3 off = collision->collision.normal * EPSILON;
+
+        for (int i = 0; i < 3; ++i) {
+
+            float& move_axis = move[i];
+            float& vel_axis = velocity[i];
+
+            const float diff = pos[i] - off[i];
+            move_axis -= diff;
+
+            vel_axis -= collision->collision.normal[i] *
+                        glm::dot(velocity, collision->collision.normal);
+            move_axis -= collision->collision.normal[i] *
+                         glm::dot(move, collision->collision.normal);
+
+            vel_axis = std::abs(vel_axis) <= EPSILON ? 0.0f : vel_axis;
+            move_axis = std::abs(move_axis) <= EPSILON ? 0.0f : move_axis;
+
+            if (abs(pos[i]) <= EPSILON2) {
+                continue;
+            }
+
+            local_pos[i] += diff; // add movement to current position
+            aabb.min[i] += diff;
+            aabb.max[i] += diff;
+        }
+    }
+}
+
+static void handle_movement(shared::animate& animate, const blocks& blocks,
+                            const aabb& aabb, const vectors& vectors,
+                            const entity::index_t& commands,
+                            const float max_time) noexcept {
+
+    auto& velocity = animate.get_mutable_velocity();
+    auto& position = animate.get_mutable_local_pos();
+
+    decelerate(velocity, blocks, aabb, commands, max_time);
+
+    const glm::vec3 accel = get_accel(blocks, aabb, vectors, commands);
+    const glm::vec3 move = animate.get_velocity() * max_time +
+                           0.5f * accel * std::pow(max_time, 2.0f);
+
+    animate.get_mutable_velocity() += accel * max_time;
+
+    handle_collisions(velocity, position, move, blocks, aabb, commands,
+                      max_time);
+}
+
+shared::animate move(const shared::moveable& moveable, const blocks& blocks,
+                     const std::uint32_t& tickrate) noexcept {
+
+    const movement::aabb& aabb = moveable.get_aabb();
+
+    const auto vectors = [&]() -> struct vectors {
+        const auto up = glm::vec3{0.0f, 1.0f, 0.0f};
+        const auto front = moveable.get_angles().to_dir();
+        const auto right = glm::normalize(glm::cross(front, up));
+        return {.up = up, .front = front, .right = right};
+    }();
+    const float max_time = 1.0f / static_cast<float>(tickrate);
+
+    shared::animate ret = moveable;
+    handle_movement(ret, blocks, aabb, vectors, moveable.get_commands(),
+                    max_time);
+    normalise_position(ret.get_mutable_local_pos(),
+                       ret.get_mutable_chunk_pos());
+    return ret;
+}
+
+} // namespace movement
+} // namespace shared
diff --git a/src/shared/movement/movement.hh b/src/shared/movement/movement.hh
new file mode 100644
index 0000000..9c6e17d
--- /dev/null
+++ b/src/shared/movement/movement.hh
@@ -0,0 +1,75 @@
+#ifndef SHARED_MOVEMENT_MOVEMENT_HH_
+#define SHARED_MOVEMENT_MOVEMENT_HH_
+
+#include "shared/entity/animate.hh"
+#include "shared/entity/moveable.hh"
+#include "shared/math/math.hh"
+#include "shared/movement/struct.hh"
+#include "shared/shared.hh"
+#include "shared/world/chunk.hh"
+
+#include <algorithm>
+#include <array>
+#include <cstdint>
+
+#define GLM_ENABLE_EXPERIMENTAL
+#include <glm/glm.hpp>
+#include <glm/gtx/norm.hpp>
+
+namespace shared {
+namespace movement {
+
+// Returns a local pos relative to the base chunk pos, which can be negative,
+// or over 16.0f.
+glm::vec3 make_relative(const shared::math::coords& base_chunk_pos,
+                        const glm::vec3& other_local_pos,
+                        const shared::math::coords& other_chunk_pos) noexcept;
+
+void normalise_position(glm::vec3& local_pos,
+                        shared::math::coords& chunk_pos) noexcept;
+bool intersect_aabbs(const aabb& a, const aabb& b) noexcept;
+
+struct line {
+    glm::vec3 origin;
+    glm::vec3 dir;
+};
+struct ray_aabb_ret {
+    glm::vec3 position;
+    float time;
+    glm::vec3 normal;
+};
+std::optional<ray_aabb_ret> intersect_ray_aabb(const line& line,
+                                               const aabb& aabb) noexcept;
+struct moving_aabb {
+    struct aabb aabb;
+    glm::vec3 velocity;
+};
+struct moving_aabb_ret {
+    float time;
+    glm::vec3 normal;
+};
+std::optional<moving_aabb_ret>
+intersect_moving_aabbs(const moving_aabb& a, const moving_aabb& b) noexcept;
+
+// We need more information about the block during movement code.
+struct block {
+    shared::world::block block;
+    struct aabb aabb;
+    shared::math::coords chunk_pos;
+    glm::ivec3 pos;
+};
+using blocks = std::vector<block>;
+
+// Returns a vec2 describing how wide and tall the array of blocks should be (to
+// ensure you never fall through anything at variable tickrates).
+glm::ivec2 get_move_xy(const std::uint32_t& tickrate,
+                       const moveable& moveable) noexcept;
+
+[[nodiscard]] shared::animate move(const shared::moveable& moveable,
+                                   const blocks& blocks,
+                                   const std::uint32_t& tickrate) noexcept;
+
+} // namespace movement
+} // namespace shared
+
+#endif
diff --git a/src/shared/movement/struct.cc b/src/shared/movement/struct.cc
new file mode 100644
index 0000000..dd079eb
--- /dev/null
+++ b/src/shared/movement/struct.cc
@@ -0,0 +1 @@
+#include "shared/movement/struct.hh"
diff --git a/src/shared/movement/struct.hh b/src/shared/movement/struct.hh
new file mode 100644
index 0000000..7cfcc0f
--- /dev/null
+++ b/src/shared/movement/struct.hh
@@ -0,0 +1,20 @@
+#ifndef SHARED_MOVEMENT_STRUCT_HH_
+#define SHARED_MOVEMENT_STRUCT_HH_
+
+#include "glm/glm.hpp"
+
+namespace shared {
+namespace movement {
+
+constexpr float EPSILON = 0.0001f; // counteract arithmetic errors
+constexpr float EPSILON2 = EPSILON + 2 * EPSILON * EPSILON;
+
+struct aabb {
+    glm::vec3 min;
+    glm::vec3 max;
+};
+
+} // namespace movement
+} // namespace shared
+
+#endif