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refactor: split CPUBackend::Render() and CUDABackend::Render() #53

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Merged
Cle2ment merged 5 commits into from
Jun 18, 2026
Merged

refactor: split CPUBackend::Render() and CUDABackend::Render() #53

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af120d4
refactor: split CPUBackend::Render() and CUDABackend::Render() (close…
Cle2ment Jun 18, 2026
c97c698
fix: add blank line between method and member section (review feedback)
Cle2ment Jun 18, 2026
786807d
fix: capture outputBuffer in lambda after RenderCPUFallback extractio…
Cle2ment Jun 18, 2026
221190a
fix: add outputBuffer to outer lambda capture (MSVC requires explicit…
Cle2ment Jun 18, 2026
2a7685b
fix: fix indentation in RenderCPUFallback, guard BVH ISPC packing wit…
Cle2ment Jun 18, 2026
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218 changes: 109 additions & 109 deletions RayTracing/src/CPUBackend.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -47,7 +47,7 @@ void CPUBackend::Render(
m_ActiveScene = &scene;
m_ActiveCamera = &camera;
m_MaxBounces = maxBounces;

m_AccumFrameIndex = frameIndex;
if (scene.Version != m_LastBvhSceneVersion)
{
m_BVH.Build(scene);
Expand All @@ -62,71 +62,74 @@ void CPUBackend::Render(
);

#ifdef PN_ISPC
// ═══════════════════════════════════════════════
// ISPC-Accelerated Path (SIMD vectorized)
// Replaces the inner pixel loop with ISPC foreach
// ═══════════════════════════════════════════════
RenderISPC(camera, scene, outputBuffer, frameIndex);
#else
RenderCPUFallback(outputBuffer);
#endif
}

#ifdef PN_ISPC
void CPUBackend::RenderISPC(const Camera& camera, const Scene& scene, uint32_t* outputBuffer, uint32_t frameIndex)
{
const uint32_t width = m_Width;
const uint32_t height = m_Height;
const size_t pixelCount = static_cast<size_t>(width) * static_cast<size_t>(height);

const auto& rayDirs = camera.GetRayDirections();
const glm::vec3& camPos = camera.GetPosition();

// ── Pack ray directions into SoA flat arrays ──
m_ISPCRayDirX.resize(pixelCount);
m_ISPCRayDirY.resize(pixelCount);
m_ISPCRayDirZ.resize(pixelCount);
for (size_t i = 0; i < pixelCount; i++) {
m_ISPCRayDirX[i] = rayDirs[i].x;
m_ISPCRayDirY[i] = rayDirs[i].y;
m_ISPCRayDirZ[i] = rayDirs[i].z;
}

// ── Pack scene spheres (SoA layout) ──
const uint32_t sphereCount = static_cast<uint32_t>(scene.Spheres.size());
if (scene.Version != m_LastISPCSceneVersion)
{
const uint32_t width = m_Width;
const uint32_t height = m_Height;
const size_t pixelCount = static_cast<size_t>(width) * static_cast<size_t>(height);

const auto& rayDirs = camera.GetRayDirections();
const glm::vec3& camPos = camera.GetPosition();

// ── Pack ray directions into SoA flat arrays ──
m_ISPCRayDirX.resize(pixelCount);
m_ISPCRayDirY.resize(pixelCount);
m_ISPCRayDirZ.resize(pixelCount);
for (size_t i = 0; i < pixelCount; i++) {
m_ISPCRayDirX[i] = rayDirs[i].x;
m_ISPCRayDirY[i] = rayDirs[i].y;
m_ISPCRayDirZ[i] = rayDirs[i].z;
m_ISCPSphPosX.resize(sphereCount);
m_ISCPSphPosY.resize(sphereCount);
m_ISCPSphPosZ.resize(sphereCount);
m_ISCPSphRadius.resize(sphereCount);
m_ISCPSphMatIdx.resize(sphereCount);
for (uint32_t i = 0; i < sphereCount; i++) {
const auto& s = scene.Spheres[i];
m_ISCPSphPosX[i] = s.Position.x;
m_ISCPSphPosY[i] = s.Position.y;
m_ISCPSphPosZ[i] = s.Position.z;
m_ISCPSphRadius[i] = s.Radius;
m_ISCPSphMatIdx[i] = s.MaterialIndex;
}

// ── Pack scene spheres (SoA layout) ──
const uint32_t sphereCount = static_cast<uint32_t>(scene.Spheres.size());
if (scene.Version != m_LastISPCSceneVersion)
{
m_ISCPSphPosX.resize(sphereCount);
m_ISCPSphPosY.resize(sphereCount);
m_ISCPSphPosZ.resize(sphereCount);
m_ISCPSphRadius.resize(sphereCount);
m_ISCPSphMatIdx.resize(sphereCount);
for (uint32_t i = 0; i < sphereCount; i++) {
const auto& s = scene.Spheres[i];
m_ISCPSphPosX[i] = s.Position.x;
m_ISCPSphPosY[i] = s.Position.y;
m_ISCPSphPosZ[i] = s.Position.z;
m_ISCPSphRadius[i] = s.Radius;
m_ISCPSphMatIdx[i] = s.MaterialIndex;
}

// ── Pack materials (SoA layout) ──
const uint32_t matCount = static_cast<uint32_t>(scene.Materials.size());
m_ISPCMatAlbedoR.resize(matCount);
m_ISPCMatAlbedoG.resize(matCount);
m_ISPCMatAlbedoB.resize(matCount);
m_ISPCMatRoughness.resize(matCount);
m_ISPCMatMetallic.resize(matCount);
m_ISPCMatEmissionR.resize(matCount);
m_ISPCMatEmissionG.resize(matCount);
m_ISPCMatEmissionB.resize(matCount);
m_ISPCMatEmissionPower.resize(matCount);
for (uint32_t i = 0; i < matCount; i++) {
const auto& m = scene.Materials[i];
m_ISPCMatAlbedoR[i] = m.Albedo.x;
m_ISPCMatAlbedoG[i] = m.Albedo.y;
m_ISPCMatAlbedoB[i] = m.Albedo.z;
m_ISPCMatRoughness[i] = m.Roughness;
m_ISPCMatMetallic[i] = m.Metallic;
m_ISPCMatEmissionR[i] = m.EmissionColor.x;
m_ISPCMatEmissionG[i] = m.EmissionColor.y;
m_ISPCMatEmissionB[i] = m.EmissionColor.z;
m_ISPCMatEmissionPower[i] = m.EmissionPower;
}
m_LastISPCSceneVersion = scene.Version;
m_ISPCMatAlbedoR.resize(matCount);
m_ISPCMatAlbedoG.resize(matCount);
m_ISPCMatAlbedoB.resize(matCount);
m_ISPCMatRoughness.resize(matCount);
m_ISPCMatMetallic.resize(matCount);
m_ISPCMatEmissionR.resize(matCount);
m_ISPCMatEmissionG.resize(matCount);
m_ISPCMatEmissionB.resize(matCount);
m_ISPCMatEmissionPower.resize(matCount);
for (uint32_t i = 0; i < matCount; i++) {
const auto& m = scene.Materials[i];
m_ISPCMatAlbedoR[i] = m.Albedo.x;
m_ISPCMatAlbedoG[i] = m.Albedo.y;
m_ISPCMatAlbedoB[i] = m.Albedo.z;
m_ISPCMatRoughness[i] = m.Roughness;
m_ISPCMatMetallic[i] = m.Metallic;
m_ISPCMatEmissionR[i] = m.EmissionColor.x;
m_ISPCMatEmissionG[i] = m.EmissionColor.y;
m_ISPCMatEmissionB[i] = m.EmissionColor.z;
m_ISPCMatEmissionPower[i] = m.EmissionPower;
}
m_LastISPCSceneVersion = scene.Version;

// ── Pack BVH (SoA layout) ──
{
Expand Down Expand Up @@ -156,58 +159,60 @@ void CPUBackend::Render(

m_ISPCBvhSphereIndices.assign(bvhSpIndices.begin(), bvhSpIndices.end());
}
}

// ── Output buffers ──
m_ISPCOutputR.resize(pixelCount);
m_ISPCOutputG.resize(pixelCount);
m_ISPCOutputB.resize(pixelCount);
m_ISPCOutputA.resize(pixelCount);

// ── Call ISPC kernel ──
ispc::ISPCRenderPixels(
camPos.x, camPos.y, camPos.z,
m_ISPCRayDirX.data(), m_ISPCRayDirY.data(), m_ISPCRayDirZ.data(),
m_ISCPSphPosX.data(), m_ISCPSphPosY.data(), m_ISCPSphPosZ.data(),
m_ISCPSphRadius.data(), m_ISCPSphMatIdx.data(),
m_ISPCMatAlbedoR.data(), m_ISPCMatAlbedoG.data(), m_ISPCMatAlbedoB.data(),
m_ISPCMatRoughness.data(), m_ISPCMatMetallic.data(),
m_ISPCMatEmissionR.data(), m_ISPCMatEmissionG.data(), m_ISPCMatEmissionB.data(),
m_ISPCMatEmissionPower.data(),
m_ISPCOutputR.data(), m_ISPCOutputG.data(), m_ISPCOutputB.data(), m_ISPCOutputA.data(),
static_cast<int32_t>(pixelCount), static_cast<int32_t>(sphereCount),
// BVH data
m_ISPCBvhMinX.data(), m_ISPCBvhMinY.data(), m_ISPCBvhMinZ.data(),
m_ISPCBvhMaxX.data(), m_ISPCBvhMaxY.data(), m_ISPCBvhMaxZ.data(),
m_ISPCBvhLeftFirst.data(), m_ISPCBvhCount.data(),
m_ISPCBvhSphereIndices.data(),
static_cast<int32_t>(m_ISPCBvhLeftFirst.size()),
static_cast<int32_t>(frameIndex), maxBounces
);

// ── Unpack: accumulate + tone map + RGBA convert ──
for (size_t i = 0; i < pixelCount; i++) {
glm::vec4 color(m_ISPCOutputR[i], m_ISPCOutputG[i], m_ISPCOutputB[i], m_ISPCOutputA[i]);
m_AccumulationData[i] += color;

glm::vec4 accumulated = m_AccumulationData[i];
accumulated /= static_cast<float>(frameIndex);
accumulated = glm::clamp(accumulated, glm::vec4(0.0f), glm::vec4(1.0f));
outputBuffer[i] = PathTracerCore::ConvertToRGBA(accumulated);
}
// ── Output buffers ──
m_ISPCOutputR.resize(pixelCount);
m_ISPCOutputG.resize(pixelCount);
m_ISPCOutputB.resize(pixelCount);
m_ISPCOutputA.resize(pixelCount);

// ── Call ISPC kernel ──
ispc::ISPCRenderPixels(
camPos.x, camPos.y, camPos.z,
m_ISPCRayDirX.data(), m_ISPCRayDirY.data(), m_ISPCRayDirZ.data(),
m_ISCPSphPosX.data(), m_ISCPSphPosY.data(), m_ISCPSphPosZ.data(),
m_ISCPSphRadius.data(), m_ISCPSphMatIdx.data(),
m_ISPCMatAlbedoR.data(), m_ISPCMatAlbedoG.data(), m_ISPCMatAlbedoB.data(),
m_ISPCMatRoughness.data(), m_ISPCMatMetallic.data(),
m_ISPCMatEmissionR.data(), m_ISPCMatEmissionG.data(), m_ISPCMatEmissionB.data(),
m_ISPCMatEmissionPower.data(),
m_ISPCOutputR.data(), m_ISPCOutputG.data(), m_ISPCOutputB.data(), m_ISPCOutputA.data(),
static_cast<int32_t>(pixelCount), static_cast<int32_t>(sphereCount),
// BVH data
m_ISPCBvhMinX.data(), m_ISPCBvhMinY.data(), m_ISPCBvhMinZ.data(),
m_ISPCBvhMaxX.data(), m_ISPCBvhMaxY.data(), m_ISPCBvhMaxZ.data(),
m_ISPCBvhLeftFirst.data(), m_ISPCBvhCount.data(),
m_ISPCBvhSphereIndices.data(),
static_cast<int32_t>(m_ISPCBvhLeftFirst.size()),
static_cast<int32_t>(frameIndex), m_MaxBounces
);

// ── Unpack: accumulate + tone map + RGBA convert ──
for (size_t i = 0; i < pixelCount; i++) {
glm::vec4 color(m_ISPCOutputR[i], m_ISPCOutputG[i], m_ISPCOutputB[i], m_ISPCOutputA[i]);
m_AccumulationData[i] += color;

glm::vec4 accumulated = m_AccumulationData[i];
accumulated /= static_cast<float>(frameIndex);
accumulated = glm::clamp(accumulated, glm::vec4(0.0f), glm::vec4(1.0f));
outputBuffer[i] = PathTracerCore::ConvertToRGBA(accumulated);
}
#else
// ── C++ Scalar / std::execution::par Fallback ──
}
#endif

void CPUBackend::RenderCPUFallback(uint32_t* outputBuffer)
{
static constexpr bool kMultithreaded = true;
m_AccumFrameIndex = frameIndex;
if constexpr (kMultithreaded) {
std::for_each(
std::execution::par,
m_ImageVerticalIterator.begin(), m_ImageVerticalIterator.end(),
[this](uint32_t y)
[this, outputBuffer](uint32_t y)
{
std::ranges::for_each(
m_ImageHorizontalIterator.begin(), m_ImageHorizontalIterator.end(),
[this, y, width = m_Width](const uint32_t x)
[this, y, outputBuffer, width = m_Width](const uint32_t x)
{
const glm::vec4 color = PerPixel(x, y);
const size_t idx = static_cast<size_t>(x) + static_cast<size_t>(y) * static_cast<size_t>(width);
Expand All @@ -217,12 +222,8 @@ void CPUBackend::Render(
glm::vec4 accumulatedColor = m_AccumulationData[idx];
accumulatedColor /= static_cast<float>(m_AccumFrameIndex);

accumulatedColor = glm::clamp(
accumulatedColor,
glm::vec4(0.0f), glm::vec4(1.0f)
);
outputBuffer[idx]
= PathTracerCore::ConvertToRGBA(accumulatedColor);
accumulatedColor = glm::clamp(accumulatedColor, glm::vec4(0.0f), glm::vec4(1.0f));
outputBuffer[idx] = PathTracerCore::ConvertToRGBA(accumulatedColor);
});
});
} else {
Expand All @@ -240,7 +241,6 @@ void CPUBackend::Render(
}
}
}
#endif // PN_ISPC
}

// ──────────────────────────────────────────────
Expand Down
5 changes: 5 additions & 0 deletions RayTracing/src/CPUBackend.h
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Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,11 @@ class CPUBackend : public IRenderBackend
) const noexcept;
static HitPayLoad Miss(const Ray& ray) noexcept;

void RenderCPUFallback(uint32_t* outputBuffer);
#ifdef PN_ISPC
void RenderISPC(const Camera& camera, const Scene& scene, uint32_t* outputBuffer, uint32_t frameIndex);
#endif

private:
uint32_t m_Width = 0;
uint32_t m_Height = 0;
Expand Down
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