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1 files changed, 321 insertions, 0 deletions

diff --git a/src/raycast.cpp b/src/raycast.cpp
new file mode 100644
index 00000000..bdd348fb
--- /dev/null
+++ b/src/raycast.cpp
@@ -0,0 +1,321 @@
+#include "raycast-diag.hpp"
+#include "pass-mode.hpp"
+#include "src/world.hpp"
+#include "src/object.hpp"
+#include "src/RTree-search.hpp"
+#include <float.h>
+#include <Corrade/Containers/StructuredBindings.h>
+#include <Corrade/Containers/GrowableArray.h>
+#include <Magnum/Math/Functions.h>
+#include <Magnum/Math/Vector2.h>
+
+namespace floormat::rc {
+
+namespace {
+
+template<typename T> constexpr inline auto tile_size = Math::Vector2<T>{iTILE_SIZE2};
+template<typename T> constexpr inline auto chunk_size = Math::Vector2<T>{TILE_MAX_DIM} * tile_size<T>;
+
+using floormat::detail_rc::bbox;
+using RTree = std::decay_t<decltype(*std::declval<struct chunk>().rtree())>;
+using Rect = typename RTree::Rect;
+
+template<class T> constexpr inline T sign_(auto&& x) {
+    constexpr auto zero = std::decay_t<decltype(x)>{0};
+    return T(x > zero) - T(x < zero);
+}
+
+constexpr Vector2 pt_to_vec(point from, point pt)
+{
+    auto V = Vector2{};
+    V += (Vector2(pt.chunk()) - Vector2(from.chunk())) * chunk_size<float>;
+    V += (Vector2(pt.local()) - Vector2(from.local())) * tile_size<float>;
+    V += (Vector2(pt.offset()) - Vector2(from.offset()));
+    return V;
+}
+
+struct aabb_result
+{
+    float tmin;
+    bool result;
+};
+
+template<typename T>
+std::array<uint8_t, 2> ray_aabb_signs(Math::Vector2<T> ray_dir_inv_norm)
+{
+    bool signs[2];
+    for (unsigned d = 0; d < 2; ++d)
+        signs[d] = std::signbit(ray_dir_inv_norm[d]);
+    return { signs[0], signs[1] };
+}
+
+// https://tavianator.com/2022/ray_box_boundary.html
+// https://www.researchgate.net/figure/The-slab-method-for-ray-intersection-detection-15_fig3_283515372
+aabb_result ray_aabb_intersection(Vector2 ray_origin, Vector2 ray_dir_inv_norm,
+                                  std::array<Vector2, 2> box_minmax, std::array<uint8_t, 2> signs)
+{
+    using Math::min;
+    using Math::max;
+
+    float tmin = 0, tmax = 16777216;
+
+    for (unsigned d = 0; d < 2; ++d)
+    {
+        auto bmin = box_minmax[signs[d]][d];
+        auto bmax = box_minmax[!signs[d]][d];
+        float dmin = (bmin - ray_origin[d]) * ray_dir_inv_norm[d];
+        float dmax = (bmax - ray_origin[d]) * ray_dir_inv_norm[d];
+
+        tmin = max(dmin, tmin);
+        tmax = min(dmax, tmax);
+    }
+
+    return { tmin, tmin < tmax };
+}
+
+struct chunk_neighbors
+{
+    chunk* array[3][3];
+};
+
+auto get_chunk_neighbors(class world& w, chunk_coords_ ch)
+{
+    chunk_neighbors nbs;
+    for (int j = 0; j < 3; j++)
+        for (int i = 0; i < 3; i++)
+            nbs.array[i][j] = w.at(ch + Vector2i(i - 1, j - 1));
+    return nbs;
+}
+
+constexpr Vector2i chunk_offsets[3][3] = {
+    {
+        { -chunk_size<int>.x(), -chunk_size<int>.y()    },
+        { -chunk_size<int>.x(),  0                      },
+        { -chunk_size<int>.x(),  chunk_size<int>.y()    },
+    },
+    {
+        { 0,                    -chunk_size<int>.y()    },
+        { 0,                     0                      },
+        { 0,                     chunk_size<int>.y()    },
+    },
+    {
+        {  chunk_size<int>.x(), -chunk_size<int>.y()    },
+        {  chunk_size<int>.x(),  0                      },
+        {  chunk_size<int>.x(),  chunk_size<int>.y()    },
+    },
+};
+//static_assert(chunk_offsets[0][0] == Vector2i(-1024, -1024));
+//static_assert(chunk_offsets[2][0] == Vector2i(1024, -1024));
+
+template<typename T>
+constexpr bool within_chunk_bounds(Math::Vector2<T> p0, Math::Vector2<T> p1)
+{
+    constexpr auto max_bb_size = Math::Vector2<T>{T{0xff}, T{0xff}};
+    constexpr auto half_bb = (max_bb_size + Math::Vector2{T{1}}) / T{2};
+    constexpr auto start = -half_bb, end = chunk_size<T> + half_bb;
+
+    return !(start.x() > p1.x() || end.x() < p0.x() ||
+             start.y() > p1.y() || end.y() < p0.y());
+}
+template bool within_chunk_bounds<int>(Math::Vector2<int> p0, Math::Vector2<int> p1);
+
+template<bool EnableDiagnostics>
+raycast_result_s do_raycasting(std::conditional_t<EnableDiagnostics, raycast_diag_s&, std::nullptr_t> diag,
+                       world& w, point from, point to, object_id self)
+{
+    raycast_result_s result;
+    fm_assert(from.chunk3().z == to.chunk3().z);
+
+    using Math::max;
+    using Math::min;
+    using Math::abs;
+    using Math::ceil;
+
+    constexpr float eps = 1e-6f;
+    constexpr float inv_eps = 1/eps;
+    constexpr int fuzz = 2;
+    constexpr auto fuzz2 = 0.5f;
+
+    result.has_result = false;
+
+    auto V = pt_to_vec(from, to);
+    auto ray_len = V.length();
+    auto dir = V.normalized();
+
+    if (abs(dir.x()) < eps && abs(dir.y()) < eps) [[unlikely]]
+        dir = {eps, eps};
+
+    unsigned long_axis, short_axis;
+
+    if (abs(dir.y()) > abs(dir.x()))
+    {
+        long_axis = 1;
+        short_axis = 0;
+    }
+    else
+    {
+        long_axis = 0;
+        short_axis = 1;
+    }
+
+    auto long_len  = max(1u, (unsigned)ceil(abs(V[long_axis]))),
+         short_len = max(1u, (unsigned)ceil(abs(V[short_axis])));
+    auto nsteps = 1u;
+    nsteps = max(nsteps, (short_len+tile_size<unsigned>.x()-1)/tile_size<unsigned>.x());
+    nsteps = max(nsteps, (long_len+chunk_size<unsigned>.x()-1)/chunk_size<unsigned>.x());
+    auto size_ = Vector2ui{};
+    size_[short_axis] = (short_len+nsteps*2-1) / nsteps;
+    size_[long_axis]  = (long_len+nsteps-1) / nsteps;
+
+    auto dir_inv_norm = Vector2(
+        abs(dir.x()) < eps ? std::copysign(inv_eps, dir.x()) : 1 / dir.x(),
+        abs(dir.y()) < eps ? std::copysign(inv_eps, dir.y()) : 1 / dir.y()
+    );
+    auto signs = ray_aabb_signs(dir_inv_norm);
+
+    result = {
+        .from = from,
+        .to = to,
+        .collision = {},
+        .collider = {
+            .tag  = (uint64_t)collision_type::none,
+            .pass = (uint64_t)pass_mode::pass,
+            .data = ((uint64_t)1 << collision_data_BITS)-1,
+        },
+        .has_result = true,
+        .success = false,
+    };
+    if constexpr(EnableDiagnostics)
+    {
+        diag = {
+            .V = V,
+            .dir = dir,
+            .dir_inv_norm = dir_inv_norm,
+            .size = size_,
+            .tmin = 0,
+        };
+        arrayResize(diag.path, 0);
+        arrayReserve(diag.path, nsteps+1);
+    }
+
+    float min_tmin = FLT_MAX;
+    bool b = true;
+
+    //Debug{} << "------";
+    for (unsigned k = 0; b && k <= nsteps; k++)
+    {
+        auto pos_ = ceil(abs(V * (float)k/(float)nsteps));
+        auto pos = Vector2i{(int)std::copysign(pos_.x(), V.x()), (int)std::copysign(pos_.y(), V.y())};
+        auto size = size_;
+
+        if (k == 0)
+        {
+            for (auto axis : { long_axis, short_axis })
+            {
+                auto sign = sign_<int>(V[axis]);
+                pos[axis] += (int)(size[axis]/4) * sign;
+                size[axis] -= size[axis]/2;
+            }
+        }
+        else if (k == nsteps)
+        {
+            constexpr auto add = (tile_size<unsigned>.x()+1)/2,
+                           min_size = tile_size<unsigned>.x() + add;
+            if (size[long_axis] > min_size)
+            {
+                auto sign = sign_<int>(V[long_axis]);
+                auto off = (int)(size[long_axis]/2) - (int)add;
+                fm_debug_assert(off >= 0);
+                pos[long_axis] -= off/2 * sign;
+                size[long_axis] -= (unsigned)off;
+            }
+        }
+
+        pos -= Vector2i(fuzz);
+        size += Vector2ui(fuzz)*2;
+
+        Vector2 origin;
+        min_tmin = FLT_MAX;
+        b = true;
+
+        const auto do_check_collider = [&](uint64_t data, const Rect& r)
+        {
+            auto x = std::bit_cast<collision_data>(data);
+            if (x.data == self || x.pass == (uint64_t)pass_mode::pass)
+                return;
+            //Debug{} << "item" << x.data << Vector2(r.m_min[0], r.m_min[1]) << Vector2(r.m_max[0], r.m_max[1]);
+            auto ret = ray_aabb_intersection(origin, dir_inv_norm,
+                                             {{{r.m_min[0]-fuzz2, r.m_min[1]-fuzz2},
+                                               {r.m_max[0]+fuzz2, r.m_max[1]+fuzz2}}},
+                                             signs);
+            if (!ret.result)
+                return;
+            if (ret.tmin > ray_len) [[unlikely]]
+                return;
+            if (ret.tmin < min_tmin) [[likely]]
+            {
+                min_tmin = ret.tmin;
+                result.collision = object::normalize_coords(from, Vector2i(dir * min_tmin));
+                result.collider = x;
+                b = false;
+            }
+        };
+
+        auto center = object::normalize_coords(from, pos);
+
+        if constexpr(EnableDiagnostics)
+            arrayAppend(diag.path, bbox{center, size});
+
+        auto last_ch = from.chunk3();
+        auto nbs = get_chunk_neighbors(w, from.chunk3());
+
+        if (center.chunk3() != last_ch) [[unlikely]]
+        {
+            last_ch = center.chunk3();
+            nbs = get_chunk_neighbors(w, center.chunk3());
+        }
+
+        auto pt = Vector2i(center.local()) * tile_size<int> + Vector2i(center.offset());
+
+        for (int i = 0; i < 3; i++)
+        {
+            for (int j = 0; j < 3; j++)
+            {
+                auto* c = nbs.array[i][j];
+                if (!c)
+                    continue;
+                auto* r = c->rtree();
+                auto off = chunk_offsets[i][j];
+                auto pt0 = pt - Vector2i(size/2), pt1 = pt0 + Vector2i(size);
+                auto pt0_ = pt0 - off, pt1_ = pt1 - off;
+                auto [fmin, fmax] = Math::minmax(Vector2(pt0_)-Vector2(fuzz2), Vector2(pt1_)+Vector2(fuzz2));
+                if (!within_chunk_bounds(fmin, fmax)) continue;
+                auto ch_off = (center.chunk() - from.chunk() + Vector2i(i-1, j-1)) * chunk_size<int>;
+                origin = Vector2((Vector2i(from.local()) * tile_size<int>) + Vector2i(from.offset()) - ch_off);
+                //Debug{} << "search" << fmin << fmax << Vector3i(c->coord());
+                r->Search(fmin.data(), fmax.data(), [&](uint64_t data, const Rect& r) {
+                    do_check_collider(data, r);
+                    return true;
+                });
+            }
+        }
+    }
+    if constexpr(EnableDiagnostics)
+        diag.tmin = b ? 0 : min_tmin;
+    result.success = b;
+    return result;
+}
+
+} // namespace
+
+raycast_result_s raycast(world& w, point from, point to, object_id self)
+{
+    return do_raycasting<false>(nullptr, w, from, to, self);
+}
+
+raycast_result_s raycast_with_diag(raycast_diag_s& diag, world& w, point from, point to, object_id self)
+{
+    return do_raycasting<true>(diag, w, from, to, self);
+}
+
+} // namespace floormat::rc