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// vischeck.cpp — world-only line-of-sight test via EngineTraceClient003.
//
// IEngineTrace::TraceRay (vtable slot 4) is given a ray from the eye to the
// aim point and a TRACE_WORLD_ONLY filter. MASK_VISIBLE ignores glass/windows
// (you can see through them) while still hitting opaque world geometry.
// Per the SDK, TRACE_WORLD_ONLY does not test static props; that is the
// deliberate trade-off for this build.
#include "hl2h.h"
#include <cstddef>
#include <cstdint>
namespace {
struct alignas(16) VectorAlignedCompat {
float x, y, z, w;
};
// Ray_t: four VectorAligned (16 bytes each) followed by two bools.
struct alignas(16) RayCompat {
VectorAlignedCompat start;
VectorAlignedCompat delta;
VectorAlignedCompat startOffset;
VectorAlignedCompat extents;
bool isRay;
bool isSwept;
};
static_assert(sizeof(VectorAlignedCompat) == 16, "VectorAligned layout");
static_assert(offsetof(RayCompat, delta) == 16, "Ray_t delta offset");
static_assert(offsetof(RayCompat, isRay) == 64, "Ray_t isRay offset");
// trace_t / CGameTrace layout (Source 2013, 32-bit):
// CBaseTrace: startpos 0, endpos 12, cplane_t plane 24 (20 bytes),
// fraction 44, contents 48, dispFlags 52, allsolid 54,
// startsolid 55
// CGameTrace: fractionleftsolid 56, csurface_t surface 60 (8 bytes),
// hitgroup 68, physicsbone 72, m_pEnt 76, hitbox 80
struct SurfaceCompat {
const char *name;
short surfaceProps;
unsigned short flags;
};
struct GameTraceCompat {
Vector startpos;
Vector endpos;
Vector normal;
float dist;
uint8_t type;
uint8_t signbits;
uint8_t pad[2];
float fraction;
int contents;
uint16_t dispFlags;
bool allsolid;
bool startsolid;
float fractionleftsolid;
SurfaceCompat surface;
int hitgroup;
short physicsbone;
void *ent;
int hitbox;
uint8_t rest[64]; // future-proof / avoid short writes
};
static_assert(offsetof(GameTraceCompat, fraction) == 44, "trace_t fraction");
static_assert(offsetof(GameTraceCompat, startsolid) == 55, "trace_t startsolid");
static_assert(offsetof(GameTraceCompat, ent) == 76, "trace_t m_pEnt");
// ITraceFilter has no virtual destructor: vtable[0] = ShouldHitEntity,
// vtable[1] = GetTraceType.
struct ITraceFilterCompat {
virtual bool ShouldHitEntity(void *pEntity, int contentsMask) = 0;
virtual int GetTraceType() const = 0;
};
struct WorldOnlyFilter : ITraceFilterCompat {
bool ShouldHitEntity(void *, int) override { return false; }
int GetTraceType() const override { return 1; } // TRACE_WORLD_ONLY
};
struct EntityFilter : ITraceFilterCompat {
void *ignore;
explicit EntityFilter(void *ig) : ignore(ig) {}
bool ShouldHitEntity(void *pEntity, int) override {
return pEntity != ignore;
}
int GetTraceType() const override { return 0; } // TRACE_EVERYTHING
};
// MASK_VISIBLE = CONTENTS_SOLID | CONTENTS_MOVEABLE | CONTENTS_OPAQUE |
// CONTENTS_IGNORE_NODRAW_OPAQUE
constexpr unsigned MASK_VISIBLE = 0x1u | 0x4000u | 0x80u | 0x2000u;
// MASK_SHOT = SOLID|MOVEABLE|MONSTER|WINDOW|DEBRIS|HITBOX
constexpr unsigned MASK_SHOT = 0x1u | 0x4000u | 0x2000000u | 0x4u |
0x4000000u | 0x40000000u;
static void make_ray(RayCompat &ray, const Vector &start, const Vector &end) {
float dx = end.x - start.x, dy = end.y - start.y, dz = end.z - start.z;
ray = RayCompat{};
ray.start = {start.x, start.y, start.z, 0.0f};
ray.delta = {dx, dy, dz, 0.0f};
ray.startOffset = {0.0f, 0.0f, 0.0f, 0.0f};
ray.extents = {0.0f, 0.0f, 0.0f, 0.0f};
ray.isRay = true;
ray.isSwept = (dx * dx + dy * dy + dz * dz) > 0.0f;
}
} // namespace
bool is_visible(const Vector &eye, const Vector &point) {
static bool warned = false;
if (!g_iface.enginetrace) {
if (!warned) {
warned = true;
logf("vischeck: EngineTraceClient003 unavailable; failing open");
}
return true;
}
RayCompat ray;
make_ray(ray, eye, point);
GameTraceCompat tr{};
WorldOnlyFilter filter;
using TraceRayFn = void (*)(void *, const RayCompat *, unsigned, void *,
GameTraceCompat *);
vfunc<TraceRayFn>(g_iface.enginetrace, 4)(g_iface.enginetrace, &ray,
MASK_VISIBLE, &filter, &tr);
return tr.fraction > 0.97f && !tr.startsolid;
}
// Trace the crosshair ray and return the first entity hit (nullptr for world
// or no hit). `ignore` is the local player entity pointer.
void *trace_entity(const Vector &start, const Vector &end, void *ignore) {
if (!g_iface.enginetrace)
return nullptr;
RayCompat ray;
make_ray(ray, start, end);
GameTraceCompat tr{};
EntityFilter filter(ignore);
using TraceRayFn = void (*)(void *, const RayCompat *, unsigned, void *,
GameTraceCompat *);
vfunc<TraceRayFn>(g_iface.enginetrace, 4)(g_iface.enginetrace, &ray,
MASK_SHOT, &filter, &tr);
if (tr.fraction >= 1.0f || tr.startsolid)
return nullptr;
return tr.ent;
}
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