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Merged
syoyo merged 3 commits into from
May 26, 2026
Merged

Add clean pure-C11 port of the lightrt_c BVH binding #3

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3537272
Add Emscripten/WASM build support for TaskSystem
syoyo May 21, 2026
580dfca
Add clean pure-C11 port of the lightrt_c BVH binding
syoyo May 21, 2026
dcb71eb
meson: add pure_c_binding option mirroring the CMake build
syoyo May 21, 2026
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30 changes: 28 additions & 2 deletions CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@
# SPDX-License-Identifier: MIT

cmake_minimum_required(VERSION 3.10)
project(lightrt VERSION 1.0.0 LANGUAGES CXX)
project(lightrt VERSION 1.0.0 LANGUAGES CXX C)

include(CTest)

Expand All @@ -12,6 +12,11 @@ set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_CXX_EXTENSIONS OFF)

# C11 standard (for the pure-C binding lightrt_c.c and its test)
set(CMAKE_C_STANDARD 11)
set(CMAKE_C_STANDARD_REQUIRED ON)
set(CMAKE_C_EXTENSIONS OFF)

# Compiler flags: no RTTI, no exceptions
if(MSVC)
# Remove default /GR to avoid override warning, keep /EHsc for MSVC
Expand Down Expand Up @@ -123,11 +128,23 @@ elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^arm")
endif()
endif()

# C binding implementation. lightrt_c.cc is a thin C++ wrapper over the C++
# BVH; lightrt_c.c is a standalone pure-C11 reimplementation. Both expose the
# same lightrt_c.h API, so exactly one is linked into the library.
option(LIGHTRT_PURE_C_BINDING
"Use the standalone pure-C11 binding (lightrt_c.c) instead of the C++ wrapper (lightrt_c.cc)"
OFF)
if(LIGHTRT_PURE_C_BINDING)
set(LIGHTRT_C_BINDING_SRC lightrt_c.c)
else()
set(LIGHTRT_C_BINDING_SRC lightrt_c.cc)
endif()

# Library target
add_library(lightrt STATIC
lightrt.cc
lightrt.hh
lightrt_c.cc
${LIGHTRT_C_BINDING_SRC}
lightrt_c.h
)

Expand All @@ -153,6 +170,15 @@ target_link_libraries(lightrt_benchmark
lightrt
)

# Pure-C11 binding self-test (compiles lightrt_c.c directly; no C++ dependency).
if(BUILD_TESTING)
add_executable(lightrt_c_test lightrt_c.c tests/test_lightrt_c.c)
if(NOT MSVC)
target_link_libraries(lightrt_c_test m)
endif()
add_test(NAME lightrt_c_test COMMAND lightrt_c_test)
endif()

option(LIGHTRT_BUILD_WEBGPU "Build WebGPU software backend targets" ON)
if(LIGHTRT_BUILD_WEBGPU)
add_subdirectory(webgpu)
Expand Down
24 changes: 24 additions & 0 deletions lightrt.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,9 @@ namespace lightrt {
// TaskSystem Implementation
// ============================================================================

#ifdef __EMSCRIPTEN__
// WASM stub: no actual threads, inline execution
#else
std::vector<std::thread> TaskSystem::threads_;
std::queue<std::function<void()>> TaskSystem::tasks_;
std::mutex TaskSystem::mutex_;
Expand All @@ -32,6 +35,7 @@ struct TaskSystemGuard {
}
};
static TaskSystemGuard g_task_system_guard;
#endif // __EMSCRIPTEN__

// ============================================================================
// Triangle Implementation
Expand Down Expand Up @@ -1497,7 +1501,11 @@ uint32_t BVH::buildRecursive(uint32_t* indices, uint32_t num_prims, uint32_t dep
// Work-stealing wait: help process tasks instead of blocking
while (!done.load()) {
if (!TaskSystem::tryProcessOne()) {
#ifndef __EMSCRIPTEN__
std::this_thread::yield();
#else
// WASM: just spin
#endif
}
}
} else {
Expand Down Expand Up @@ -9705,6 +9713,9 @@ void TriangleBVH::traverseBatch(const Ray* rays, uint32_t num_rays,
uint32_t num_threads) const noexcept {
if (num_rays == 0) return;

#ifdef __EMSCRIPTEN__
if (num_threads == 0) num_threads = 1;
#else
if (num_threads == 0) num_threads = std::thread::hardware_concurrency();
if (num_threads < 1) num_threads = 1;

Expand All @@ -9723,6 +9734,7 @@ void TriangleBVH::traverseBatch(const Ray* rays, uint32_t num_rays,
hit_prim_ids[i] = traverse(rays[i], hit_ts[i], hit_us[i], hit_vs[i]);
}
}, 64);
#endif
}

void TriangleBVH::traverseBatchAnyHit(const Ray* rays, uint32_t num_rays,
Expand All @@ -9731,6 +9743,9 @@ void TriangleBVH::traverseBatchAnyHit(const Ray* rays, uint32_t num_rays,
uint32_t num_threads) const noexcept {
if (num_rays == 0) return;

#ifdef __EMSCRIPTEN__
if (num_threads == 0) num_threads = 1;
#else
if (num_threads == 0) num_threads = std::thread::hardware_concurrency();
if (num_threads < 1) num_threads = 1;

Expand All @@ -9747,6 +9762,7 @@ void TriangleBVH::traverseBatchAnyHit(const Ray* rays, uint32_t num_rays,
hit_results[i] = traverseAnyHit(rays[i], exclude_prim_id);
}
}, 64);
#endif
}

// ============================================================================
Expand All @@ -9759,6 +9775,9 @@ void SBVH::traverseBatch(const Ray* rays, uint32_t num_rays,
uint32_t num_threads) const noexcept {
if (num_rays == 0) return;

#ifdef __EMSCRIPTEN__
if (num_threads == 0) num_threads = 1;
#else
if (num_threads == 0) num_threads = std::thread::hardware_concurrency();
if (num_threads < 1) num_threads = 1;

Expand All @@ -9777,6 +9796,7 @@ void SBVH::traverseBatch(const Ray* rays, uint32_t num_rays,
hit_prim_ids[i] = traverse(rays[i], hit_ts[i], hit_us[i], hit_vs[i]);
}
}, 64);
#endif
}

void SBVH::traverseBatchAnyHit(const Ray* rays, uint32_t num_rays,
Expand All @@ -9785,6 +9805,9 @@ void SBVH::traverseBatchAnyHit(const Ray* rays, uint32_t num_rays,
uint32_t num_threads) const noexcept {
if (num_rays == 0) return;

#ifdef __EMSCRIPTEN__
if (num_threads == 0) num_threads = 1;
#else
if (num_threads == 0) num_threads = std::thread::hardware_concurrency();
if (num_threads < 1) num_threads = 1;
Comment on lines +9808 to 9812

Expand All @@ -9801,6 +9824,7 @@ void SBVH::traverseBatchAnyHit(const Ray* rays, uint32_t num_rays,
hit_results[i] = traverseAnyHit(rays[i], exclude_prim_id);
}
}, 64);
#endif
}

// ============================================================================
Expand Down
24 changes: 23 additions & 1 deletion lightrt.hh
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Original file line number Diff line number Diff line change
Expand Up @@ -19,12 +19,16 @@
#include <vector>
#include <limits>
#include <cmath>
#ifndef __EMSCRIPTEN__
#include <thread>
#include <mutex>
#include <condition_variable>
#endif
#include <atomic>
#include <functional>
#ifndef __EMSCRIPTEN__
#include <queue>
#endif

// SIMD detection
#if defined(__x86_64__) || defined(_M_X64) || defined(__i386__) || defined(_M_IX86)
Expand Down Expand Up @@ -66,6 +70,21 @@ constexpr uint32_t kInvalidIndex = 0xFFFFFFFF;
// Task System (Simple Thread Pool)
// ============================================================================

#ifdef __EMSCRIPTEN__
// WASM stub: threads not available, run tasks inline
class TaskSystem {
public:
static void initialize(uint32_t = 0) {}
static void shutdown() {}
static void submit(std::function<void()> task) { task(); }
static bool tryProcessOne() { return false; }
static void parallelFor(uint32_t start, uint32_t end,
std::function<void(uint32_t, uint32_t)> body,
uint32_t = 1024) {
body(start, end);
}
};
#else
class TaskSystem {
public:
// Initialize with hardware concurrency
Expand Down Expand Up @@ -127,7 +146,9 @@ public:

// Parallel For Loop
// splits range [start, end) into chunks and runs them in parallel
static void parallelFor(uint32_t start, uint32_t end, std::function<void(uint32_t, uint32_t)> body, uint32_t min_chunk_size = 1024) {
static void parallelFor(uint32_t start, uint32_t end,
std::function<void(uint32_t, uint32_t)> body,
uint32_t min_chunk_size = 1024) {
if (threads_.empty()) {
body(start, end);
return;
Expand Down Expand Up @@ -184,6 +205,7 @@ private:
static std::condition_variable condition_;
static bool stop_;
};
#endif // __EMSCRIPTEN__

// ============================================================================
// Vector Math
Expand Down
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