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#include "shared/pch.hh"
#include "shared/entity/collision.hh"
#include "core/math/constexpr.hh"
#include "shared/entity/gravity.hh"
#include "shared/entity/grounded.hh"
#include "shared/entity/transform.hh"
#include "shared/entity/velocity.hh"
#include "shared/world/dimension.hh"
#include "shared/world/voxel_registry.hh"
#include "shared/coord.hh"
#include "shared/globals.hh"
static int vgrid_collide(const Dimension* dimension, int d, Collision& collision, Transform& transform, Velocity& velocity,
VoxelMaterial& touch_surface, bool enable_snapping_to_grid)
{
auto movespeed = globals::fixed_frametime * velocity.value[d];
auto movesign = math::sign<int>(movespeed);
auto& ref_aabb = collision.aabb;
auto ref_center = 0.5f * ref_aabb.min + 0.5f * ref_aabb.max;
auto ref_halfsize = 0.5f * ref_aabb.max - 0.5f * ref_aabb.min;
auto curr_aabb = ref_aabb.push(transform.local);
math::AABBf next_aabb(curr_aabb);
next_aabb.min[d] += movespeed;
next_aabb.max[d] += movespeed;
auto next_center = 0.5f * next_aabb.min + 0.5f * next_aabb.max;
auto csg_aabb = curr_aabb.combine(next_aabb);
local_pos lpos_min;
lpos_min.x = static_cast<local_pos::value_type>(glm::floor(csg_aabb.min.x));
lpos_min.y = static_cast<local_pos::value_type>(glm::floor(csg_aabb.min.y));
lpos_min.z = static_cast<local_pos::value_type>(glm::floor(csg_aabb.min.z));
local_pos lpos_max;
lpos_max.x = static_cast<local_pos::value_type>(glm::ceil(csg_aabb.max.x));
lpos_max.y = static_cast<local_pos::value_type>(glm::ceil(csg_aabb.max.y));
lpos_max.z = static_cast<local_pos::value_type>(glm::ceil(csg_aabb.max.z));
auto u = (d + 1) % 3;
auto v = (d + 2) % 3;
local_pos::value_type ddir;
local_pos::value_type dmin;
local_pos::value_type dmax;
if(movespeed < 0.0f) {
ddir = local_pos::value_type(+1);
dmin = lpos_min[d];
dmax = lpos_max[d];
}
else {
ddir = local_pos::value_type(-1);
dmin = lpos_max[d];
dmax = lpos_min[d];
}
auto closest_dist = std::numeric_limits<float>::infinity();
auto closest_touch = VTOUCH_NONE;
auto closest_surface = VMAT_UNKNOWN;
auto closest_tvalues = ZERO_VEC3<float>;
math::AABBf closest_vbox;
for(auto i = dmin; i != dmax; i += ddir) {
for(auto j = lpos_min[u]; j < lpos_max[u]; ++j) {
for(auto k = lpos_min[v]; k < lpos_max[v]; ++k) {
local_pos lpos;
lpos[d] = i;
lpos[u] = j;
lpos[v] = k;
auto vpos = coord::to_voxel(transform.chunk, lpos);
auto voxel = dimension->get_voxel(vpos);
if(voxel == nullptr || voxel->is_touch_type<VTOUCH_NONE>()) {
continue; // non-collidable
}
auto vbox = voxel->get_collision().push(lpos);
auto vbox_center = 0.5f * vbox.min + 0.5f * vbox.max;
if(!csg_aabb.intersect(vbox)) {
continue; // no intersection
}
auto distance = glm::abs(vbox_center[d] - next_center[d]);
if(distance < closest_dist) {
closest_dist = distance;
closest_touch = voxel->get_touch_type();
closest_surface = voxel->get_surface_material();
closest_tvalues = voxel->get_touch_values();
closest_vbox = vbox;
}
}
}
}
if(std::isfinite(closest_dist)) {
auto snap_to_closest_vbox = false;
if(closest_touch == VTOUCH_BOUNCE) {
auto threshold = 2.0f * static_cast<float>(globals::fixed_frametime);
auto travel_distance = glm::abs(curr_aabb.min[d] - next_aabb.min[d]);
if(travel_distance > threshold) {
velocity.value[d] = -velocity.value[d] * closest_tvalues[d];
}
else {
velocity.value[d] = 0.0f;
}
snap_to_closest_vbox = true;
}
else if(closest_touch == VTOUCH_SINK) {
constexpr auto threshold = 0.01f;
if(velocity.value[d] < threshold) {
velocity.value[d] = 0.0f;
}
else {
velocity.value[d] *= closest_tvalues[d];
}
}
else {
velocity.value[d] = 0.0f;
snap_to_closest_vbox = true;
}
if(snap_to_closest_vbox && enable_snapping_to_grid) {
auto vbox_center = 0.5f * closest_vbox.min[d] + 0.5f * closest_vbox.max[d];
auto vbox_halfsize = 0.5f * closest_vbox.max[d] - 0.5f * closest_vbox.min[d];
if(movesign < 0) {
transform.local[d] = vbox_center + vbox_halfsize + ref_halfsize[d] - ref_center[d] + 0.01f * globals::fixed_frametime;
}
else {
transform.local[d] = vbox_center - vbox_halfsize - ref_halfsize[d] - ref_center[d] - 0.01f * globals::fixed_frametime;
}
}
touch_surface = closest_surface;
return movesign;
}
touch_surface = VMAT_UNKNOWN;
return 0;
}
void Collision::fixed_update(Dimension* dimension)
{
auto group = dimension->entities.group<Collision>(entt::get<Transform, Velocity>);
for(auto [entity, collision, transform, velocity] : group.each()) {
auto surface = VMAT_UNKNOWN;
auto vertical_move = vgrid_collide(dimension, 1, collision, transform, velocity, surface, true);
if(dimension->entities.any_of<Gravity>(entity)) {
if(vertical_move == math::sign<int>(dimension->get_gravity())) {
dimension->entities.emplace_or_replace<Grounded>(entity, Grounded { surface });
}
else {
dimension->entities.remove<Grounded>(entity);
}
}
else {
// The entity cannot be grounded because the component
// setup of said entity should not let it comprehend the
// concept of resting on the ground (it flies around)
dimension->entities.remove<Grounded>(entity);
}
vgrid_collide(dimension, 0, collision, transform, velocity, surface, false);
vgrid_collide(dimension, 2, collision, transform, velocity, surface, false);
}
}
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