feat: 环境背景管线（IBL 阶段①）——HDR 等距柱状转 cube + Skybox pass

- Cubemap：stbi_loadf 加载 .hdr，CPU 双线性重采样 6 面（GL 规范方向表），
  f32→fp16 转换后整块上传 eCubeCompatible image（R16G16B16A16Sfloat）
- SkyboxPass：HDRColor 的 first writer，承担清屏职责；无环境贴图自动
  退化为纯清屏（Forward 不受影响）
- frag 逐像素 NDC 反投影取世界方向（invVP push，投影变换不可线性插值）
- Forward color 附件 Clear→Load：几何合成在天空之上
- SceneRenderer 产出 skyInvVP = inverse(proj × mat4(mat3(view)))

Engine/include/Engine/Renderer/Cubemap.h

@@ -0,0 +1,59 @@
+//
+// Created by atdunbg on 2026/9/23.
+//
+// Cubemap：环境立方体贴图。
+//
+// 从等距柱状 HDR（.hdr，polyhaven 等）生成：CPU 重采样到 6 面
+//（一次性加载成本，亚秒级），转 fp16 后整块上传，硬件 Cube 采样。
+// 后续 IBL 的 irradiance/prefilter 卷积也基于本类的数据形态。
+//
+
+#ifndef HELLOVULKAN_CUBEMAP_H
+#define HELLOVULKAN_CUBEMAP_H
+
+#include <Engine/Core/Types.h>
+#include <Engine/Vulkan/MemoryAllocator.h>
+#include <vulkan/vulkan.hpp>
+
+namespace Engine {
+
+    class Device;
+
+    class Cubemap {
+    public:
+        // 从等距柱状 HDR 生成（CPU 重采样到 6 面，faceSize 为每面边长）
+        static Scope<Cubemap> CreateFromHdrEquirect(Device& device,
+                                                    MemoryAllocator& allocator,
+                                                    const std::string& path,
+                                                    u32 faceSize);
+
+        ~Cubemap();
+
+        Cubemap(const Cubemap&) = delete;
+        Cubemap& operator=(const Cubemap&) = delete;
+
+        vk::Image Get() const { return m_Image; }
+        vk::ImageView GetView() const { return m_View; }
+        vk::Sampler GetSampler() const { return m_Sampler; }
+        u32 GetFaceSize() const { return m_FaceSize; }
+
+    private:
+        Cubemap(Device& device, MemoryAllocator& allocator,
+                vk::Image image, vk::ImageView view, vk::Sampler sampler,
+                MemoryAllocator::Allocation allocation, u32 faceSize)
+            : m_Device(device), m_Allocator(allocator),
+              m_Image(image), m_View(view), m_Sampler(sampler),
+              m_Allocation(allocation), m_FaceSize(faceSize) {}
+
+        Device& m_Device;
+        MemoryAllocator& m_Allocator;
+        vk::Image m_Image;
+        vk::ImageView m_View;
+        vk::Sampler m_Sampler;
+        MemoryAllocator::Allocation m_Allocation;
+        u32 m_FaceSize;
+    };
+
+} // namespace Engine
+
+#endif //HELLOVULKAN_CUBEMAP_H

Engine/include/Engine/Renderer/Passes/SkyboxPass.h

@@ -0,0 +1,61 @@
+//
+// Created by atdunbg on 2026/9/23.
+//
+// SkyboxPass：环境背景（IBL 阶段①）。
+//
+// HDRColor 的 first writer：承担清屏职责（loadOp Clear），有环境贴图时
+// 再画天空——Forward 随之改为 loadOp Load，几何在天空之上合成。
+// 职责收口对齐 UE：sky pass 是场景渲染的第一步，无深度附件，
+// 深度测试关（几何完全覆盖由 Forward 的深度决定）。
+//
+// 环境贴图生命周期：Renderer 持有 Cubemap（声明序先于 pass），
+// 本 pass 只引用。描述符绑定一次（cube view 全程稳定，不随 RG 重编译）。
+//
+
+#ifndef HELLOVULKAN_SKYBOXPASS_H
+#define HELLOVULKAN_SKYBOXPASS_H
+
+#include <Engine/Core/FrameContext.h>
+#include <Engine/Renderer/Passes/RenderPass.h>
+#include <Engine/Renderer/SceneTypes.h>
+#include <vulkan/vulkan.hpp>
+
+namespace Engine {
+
+    class Device;
+    class DescriptorManager;
+    class ShaderManager;
+    class Cubemap;
+
+    namespace Passes {
+
+        class SkyboxPass final : public RenderPass {
+        public:
+            // env 可为空（HDR 资产缺失）：仅承担清屏，天空保持清屏色
+            SkyboxPass(Device& device, ShaderManager& shaders,
+                       DescriptorManager& descriptors, FrameSceneData& frame,
+                       RG::TextureHandle hdrColor, const Cubemap* env);
+            ~SkyboxPass();
+
+            SkyboxPass(const SkyboxPass&) = delete;
+            SkyboxPass& operator=(const SkyboxPass&) = delete;
+
+            void Register(RG::RenderGraph& rg) override;
+
+        private:
+            Device& m_Device;
+            DescriptorManager& m_Descriptors;
+            FrameSceneData& m_Frame;
+            RG::TextureHandle m_HDRColor;
+            const Cubemap* m_Env;   // 可空
+
+            vk::DescriptorSetLayout m_SetLayout;   // Set0 = {samplerCube}
+            vk::PipelineLayout m_Layout;           // push = invVP 64B
+            vk::ShaderEXT m_Vert{}, m_Frag{};
+            std::array<vk::DescriptorSet, kMaxFramesInFlight> m_Sets{};
+        };
+
+    } // namespace Passes
+} // namespace Engine
+
+#endif //HELLOVULKAN_SKYBOXPASS_H

Engine/include/Engine/Renderer/Renderer.h

@@ -41,6 +41,7 @@ namespace Engine {
     class UniformBuffer;
     class SceneRenderer;
     class VulkanAssetUploader;
+    class Cubemap;
     class ImGuiLayer;
 
     namespace ECS { class Scene; }
@@ -113,6 +114,9 @@ namespace Engine {
         Scope<UniformBuffer> m_PrevObjectBuffer; // 上一帧实例矩阵 ring（TAA velocity）
         Scope<Passes::SceneGpu> m_SceneGpu;     // 场景类 pass 共享装配
         Scope<Passes::FullscreenGpu> m_FullscreenGpu;  // 全屏 pass 共享装配
+        // 环境贴图（IBL 阶段①）：HDR → cube，被 SkyboxPass 引用；
+        // 声明在 m_Passes 之前 → 析构晚于 pass（引用安全）
+        Scope<Cubemap> m_Environment;
         Scope<Swapchain> m_Swapchain;
         Scope<SyncManager> m_SyncManager;
         Scope<CommandManager> m_CommandManager;

Engine/include/Engine/Renderer/SceneTypes.h

@@ -68,6 +68,10 @@ namespace Engine {
     struct FrameSceneData {
         UniformBufferObject ubo{};
 
+        // 天空盒反投影矩阵：inverse(projNoJitter × mat4(mat3(view)))
+        //（视图去平移只留旋转 → 反投影结果即世界方向；Skybox pass push）
+        glm::mat4 skyInvVP{1.0f};
+
         // 实例矩阵数组 = [主视图段 | 阴影视图段]（共享同一 per-slot SSBO）
         std::vector<glm::mat4> instanceModels;
         // 上一帧世界矩阵，与 instanceModels 平行对齐（同一下标 = 同一

Engine/src/Renderer/Cubemap.cpp

@@ -0,0 +1,293 @@
+//
+// Created by atdunbg on 2026/9/23.
+//
+// Cubemap 实现：HDR 等距柱状 → CPU 重采样 6 面 → fp16 → cube image。
+//
+// 一次性加载成本（亚秒级 CPU 重采样），换取运行时零转换开销；
+// 硬件 Cube 采样（filtering/边缘接缝由 driver 处理）。
+// 后续 IBL 阶段的 irradiance/prefilter 卷积复用 FaceDir 方向表。
+//
+
+#include <Engine/Renderer/Cubemap.h>
+#include <Engine/Vulkan/Device.h>
+#include <Engine/Vulkan/MemoryAllocator.h>
+#include <Engine/Core/Log.h>
+
+#include <stb/stb_image.h>
+
+#include <glm/glm.hpp>
+#include <glm/gtc/constants.hpp>
+
+#include <algorithm>
+#include <bit>
+#include <cmath>
+#include <cstring>
+#include <vector>
+
+namespace Engine
+{
+    namespace
+    {
+        constexpr u32 kFaceCount = 6;
+
+        // GL/Vulkan 规范的 cube 面方向表（与 GL spec 立方体选择表互逆）。
+        // (u,v)∈[0,1]（u 向右 v 向下）→ s,t∈[-1,1] → 单位化前方向。
+        // Vulkan 面序与 GL 一致：+X -X +Y -Y +Z -Z
+        glm::vec3 FaceDir(u32 face, f32 u, f32 v)
+        {
+            const f32 s = u * 2.0f - 1.0f;
+            const f32 t = v * 2.0f - 1.0f;
+            switch (face) {
+                case 0:  return { 1.0f, -t, -s };   // +X（面片顶行 = +Y）
+                case 1:  return {-1.0f, -t,  s };   // -X
+                case 2:  return { s, 1.0f,  t };    // +Y
+                case 3:  return { s,-1.0f, -t };    // -Y
+                case 4:  return { s, -t, 1.0f };    // +Z
+                default: return {-s, -t,-1.0f };    // -Z
+            }
+        }
+
+        // 等距柱状双线性采样（x 环绕跨经度接缝，y 钳制到极点）。
+        // 图像行 0 = 天顶（+Y）：v = acos(y)/π，与 stbi 行序一致，无需翻转
+        glm::vec3 SampleEquirect(const f32* img, u32 w, u32 h, const glm::vec3& dir)
+        {
+            const f32 u = std::atan2(dir.z, dir.x) * (0.5f / glm::pi<f32>()) + 0.5f;
+            const f32 v = std::acos(glm::clamp(dir.y, -1.0f, 1.0f)) / glm::pi<f32>();
+
+            const f32 fx = u * static_cast<f32>(w) - 0.5f;
+            const f32 fy = v * static_cast<f32>(h) - 0.5f;
+            const u32 x0 = static_cast<u32>(std::floor(fx));
+            const u32 y0 = static_cast<u32>(std::floor(fy));
+            const f32 tx = fx - std::floor(fx);
+            const f32 ty = fy - std::floor(fy);
+
+            auto fetch = [&](u32 x, u32 y) {
+                const u32 xc = ((x % w) + w) % w;           // 经度环绕
+                const u32 yc = glm::clamp(y, 0u, h - 1u);   // 纬度钳制
+                const size_t off = (static_cast<size_t>(yc) * w + xc) * 4;
+                return glm::vec3(img[off + 0], img[off + 1], img[off + 2]);
+            };
+
+            const glm::vec3 c00 = fetch(x0,     y0);
+            const glm::vec3 c10 = fetch(x0 + 1, y0);
+            const glm::vec3 c01 = fetch(x0,     y0 + 1);
+            const glm::vec3 c11 = fetch(x0 + 1, y0 + 1);
+
+            return glm::mix(glm::mix(c00, c10, tx), glm::mix(c01, c11, tx), ty);
+        }
+
+        // IEEE754 f32 → fp16（round-to-nearest-even；溢出饱和为 Inf）。
+        // HDR 环境值域内常规路径足够，次正规/NaN 路径只为数学完备
+        u16 FloatToHalf(f32 value)
+        {
+            const u32 x = std::bit_cast<u32>(value);
+            const u16 sign = static_cast<u16>((x >> 16) & 0x8000u);
+            const u32 absVal = x & 0x7fffffffu;
+
+            if (absVal > 0x7f800000u) {
+                return static_cast<u16>(sign | 0x7e00u);            // NaN
+            }
+            if (absVal >= 0x47800000u) {
+                return static_cast<u16>(sign | 0x7c00u);            // Inf / 溢出饱和
+            }
+            if (absVal >= 0x38800000u) {
+                // 常规数：指数重偏（127→15），尾数右移 13 位并舍入到最近偶数
+                const u32 bits = absVal - 0x38000000u;
+                const u32 round = 0x0fffu + ((bits >> 13) & 1u);
+                return static_cast<u16>(sign | ((bits + round) >> 13));
+            }
+            if (absVal < 0x33000000u) {
+                return sign;   // < 2^-25：舍入为 0
+            }
+            // half 次正规 [2^-24, 2^-14)：补隐含位后按目标精度舍入
+            const u32 mantissa = (absVal & 0x007fffffu) | 0x00800000u;
+            const u32 shift = 126u - (absVal >> 23u);
+            const u32 m = (mantissa + (1u << (shift - 1))) >> shift;
+            // 舍入进位到 0x400 恰好是最小正规 half 的位型，无需特判
+            return static_cast<u16>(sign | std::min(m, 0x400u));
+        }
+    }
+
+    Scope<Cubemap> Cubemap::CreateFromHdrEquirect(Device& device,
+                                                  MemoryAllocator& allocator,
+                                                  const std::string& path,
+                                                  u32 faceSize)
+    {
+        // ---- 1. CPU 加载 HDR（float RGBA）----
+        int w = 0, h = 0, channels = 0;
+        f32* pixels = stbi_loadf(path.c_str(), &w, &h, &channels, STBI_rgb_alpha);
+        if (!pixels) {
+            ENGINE_ERROR("Cubemap: failed to load HDR: {}", path);
+            return nullptr;
+        }
+        const u32 srcW = static_cast<u32>(w);
+        const u32 srcH = static_cast<u32>(h);
+
+        // ---- 2. 重采样 6 面 + fp16（RGBA16F = 每像素 8B）----
+        const u32 facePixels = faceSize * faceSize;
+        std::vector<u16> faces(kFaceCount * facePixels * 4);
+        for (u32 f = 0; f < kFaceCount; ++f) {
+            u16* dst = faces.data() + f * facePixels * 4;
+            for (u32 y = 0; y < faceSize; ++y) {
+                for (u32 x = 0; x < faceSize; ++x) {
+                    const f32 u = (static_cast<f32>(x) + 0.5f) / static_cast<f32>(faceSize);
+                    const f32 v = (static_cast<f32>(y) + 0.5f) / static_cast<f32>(faceSize);
+                    const glm::vec3 rgb =
+                        SampleEquirect(pixels, srcW, srcH, FaceDir(f, u, v));
+                    u16* px = dst + (static_cast<size_t>(y) * faceSize + x) * 4;
+                    px[0] = FloatToHalf(rgb.r);
+                    px[1] = FloatToHalf(rgb.g);
+                    px[2] = FloatToHalf(rgb.b);
+                    px[3] = 0x3C00;   // 1.0
+                }
+            }
+        }
+        stbi_image_free(pixels);
+
+        // ---- 3. staging（HOST_VISIBLE 持久映射，逐面偏移拷入）----
+        const vk::DeviceSize faceBytes =
+            static_cast<vk::DeviceSize>(facePixels) * 8;
+        const vk::DeviceSize total = faceBytes * kFaceCount;
+
+        auto stagingAlloc = allocator.CreateBuffer(
+            total,
+            vk::BufferUsageFlagBits::eTransferSrc,
+            vk::MemoryPropertyFlagBits::eHostVisible |
+            vk::MemoryPropertyFlagBits::eHostCoherent);
+        std::memcpy(stagingAlloc.MappedPtr, faces.data(),
+                    static_cast<size_t>(total));
+        faces.clear();
+        faces.shrink_to_fit();   // CPU 侧临时数据尽早释放
+
+        // ---- 4. cube image（eCubeCompatible，6 层，fp16）----
+        vk::ImageCreateInfo imageInfo;
+        imageInfo.setImageType(vk::ImageType::e2D)
+                 .setFormat(vk::Format::eR16G16B16A16Sfloat)
+                 .setExtent({faceSize, faceSize, 1})
+                 .setMipLevels(1)
+                 .setArrayLayers(kFaceCount)
+                 .setSamples(vk::SampleCountFlagBits::e1)
+                 .setTiling(vk::ImageTiling::eOptimal)
+                 .setFlags(vk::ImageCreateFlagBits::eCubeCompatible)
+                 .setUsage(vk::ImageUsageFlagBits::eTransferDst |
+                           vk::ImageUsageFlagBits::eSampled)
+                 .setSharingMode(vk::SharingMode::eExclusive)
+                 .setInitialLayout(vk::ImageLayout::eUndefined);
+
+        auto imageAlloc = allocator.CreateImage(imageInfo,
+            vk::MemoryPropertyFlagBits::eDeviceLocal);
+        const vk::Image image = imageAlloc.Image;
+
+        // ---- 5. cube view + 环境采样器（clamp-to-edge：cube 采样寻址由面自动处理）----
+        vk::ImageViewCreateInfo viewInfo;
+        viewInfo.setImage(image)
+                .setViewType(vk::ImageViewType::eCube)
+                .setFormat(vk::Format::eR16G16B16A16Sfloat)
+                .setSubresourceRange({
+                    vk::ImageAspectFlagBits::eColor, 0, 1, 0, kFaceCount});
+        vk::ImageView view = device.GetDevice().createImageView(viewInfo);
+
+        vk::SamplerCreateInfo samplerInfo;
+        samplerInfo.setMagFilter(vk::Filter::eLinear)
+                   .setMinFilter(vk::Filter::eLinear)
+                   .setMipmapMode(vk::SamplerMipmapMode::eNearest)
+                   .setAddressModeU(vk::SamplerAddressMode::eClampToEdge)
+                   .setAddressModeV(vk::SamplerAddressMode::eClampToEdge)
+                   .setAddressModeW(vk::SamplerAddressMode::eClampToEdge)
+                   .setAnisotropyEnable(VK_FALSE)
+                   .setBorderColor(vk::BorderColor::eIntOpaqueBlack)
+                   .setUnnormalizedCoordinates(VK_FALSE)
+                   .setCompareEnable(VK_FALSE)
+                   .setMinLod(0.0f)
+                   .setMaxLod(0.0f);
+        vk::Sampler sampler = device.GetDevice().createSampler(samplerInfo);
+
+        // ---- 6. 一次性命令缓冲：整 cube → TransferDst，逐面拷贝 → ShaderRead ----
+        vk::CommandPoolCreateInfo poolInfo;
+        poolInfo.setQueueFamilyIndex(device.GetGraphicsFamily())
+                .setFlags(vk::CommandPoolCreateFlagBits::eTransient);
+        vk::CommandPool pool = device.GetDevice().createCommandPool(poolInfo);
+
+        vk::CommandBuffer cmd = device.GetDevice().allocateCommandBuffers(
+            vk::CommandBufferAllocateInfo{}
+                .setCommandPool(pool)
+                .setLevel(vk::CommandBufferLevel::ePrimary)
+                .setCommandBufferCount(1))[0];
+
+        cmd.begin(vk::CommandBufferBeginInfo{
+            vk::CommandBufferUsageFlagBits::eOneTimeSubmit});
+
+        // 6 层一起转 layout（subresource range layerCount = 6）
+        vk::ImageMemoryBarrier2 toTransfer;
+        toTransfer.setSrcStageMask(vk::PipelineStageFlagBits2::eNone)
+                  .setSrcAccessMask(vk::AccessFlagBits2::eNone)
+                  .setDstStageMask(vk::PipelineStageFlagBits2::eTransfer)
+                  .setDstAccessMask(vk::AccessFlagBits2::eTransferWrite)
+                  .setOldLayout(vk::ImageLayout::eUndefined)
+                  .setNewLayout(vk::ImageLayout::eTransferDstOptimal)
+                  .setImage(image)
+                  .setSubresourceRange({vk::ImageAspectFlagBits::eColor,
+                                        0, 1, 0, kFaceCount});
+        cmd.pipelineBarrier2(
+            vk::DependencyInfo{}.setImageMemoryBarriers(toTransfer));
+
+        for (u32 f = 0; f < kFaceCount; ++f) {
+            vk::BufferImageCopy region;
+            region.setBufferOffset(faceBytes * f)
+                  .setBufferRowLength(0)
+                  .setBufferImageHeight(0)
+                  .setImageSubresource({vk::ImageAspectFlagBits::eColor,
+                                        0, f, 1})
+                  .setImageOffset({0, 0, 0})
+                  .setImageExtent({faceSize, faceSize, 1});
+            cmd.copyBufferToImage(stagingAlloc.Buffer, image,
+                                  vk::ImageLayout::eTransferDstOptimal, region);
+        }
+
+        vk::ImageMemoryBarrier2 toShader;
+        toShader.setSrcStageMask(vk::PipelineStageFlagBits2::eTransfer)
+                .setSrcAccessMask(vk::AccessFlagBits2::eTransferWrite)
+                .setDstStageMask(vk::PipelineStageFlagBits2::eFragmentShader)
+                .setDstAccessMask(vk::AccessFlagBits2::eShaderRead)
+                .setOldLayout(vk::ImageLayout::eTransferDstOptimal)
+                .setNewLayout(vk::ImageLayout::eShaderReadOnlyOptimal)
+                .setImage(image)
+                .setSubresourceRange({vk::ImageAspectFlagBits::eColor,
+                                      0, 1, 0, kFaceCount});
+        cmd.pipelineBarrier2(
+            vk::DependencyInfo{}.setImageMemoryBarriers(toShader));
+
+        cmd.end();
+
+        // ---- 7. 提交并等待，清理 staging ----
+        vk::Fence fence = device.GetDevice().createFence({});
+        device.GetGraphicsQueue().submit(
+            vk::SubmitInfo{}.setCommandBuffers(cmd), fence);
+        if (device.GetDevice().waitForFences(fence, VK_TRUE, UINT64_MAX) !=
+            vk::Result::eSuccess) {
+            ENGINE_ERROR("Cubemap upload: waitForFences failed");
+        }
+
+        device.GetDevice().destroyFence(fence);
+        device.GetDevice().destroyCommandPool(pool);
+        allocator.Destroy(stagingAlloc);
+
+        ENGINE_INFO("Environment cubemap: {} ({}x6 {} faces, fp16)",
+                    path, faceSize, kFaceCount);
+
+        return Scope<Cubemap>(new Cubemap(device, allocator, image, view,
+                                          sampler, imageAlloc, faceSize));
+    }
+
+    Cubemap::~Cubemap()
+    {
+        const auto& vkDevice = m_Device.GetDevice();
+
+        vkDevice.destroySampler(m_Sampler);
+        vkDevice.destroyImageView(m_View);
+
+        // image 资源与显存经 VMA 成对释放
+        m_Allocator.Destroy(m_Allocation);
+    }
+
+} // namespace Engine

Engine/src/Renderer/Passes/ForwardPass.cpp

@@ -22,9 +22,10 @@ namespace Engine::Passes
                 std::array<float, 4>{0.1f, 0.1f, 0.1f, 0.0f});
 
             vk::RenderingAttachmentInfo colorAttachments[2];
+            // HDR 附件由 Skybox pass 清屏并画背景，这里 Load 在其上合成几何
             colorAttachments[0].setImageView(ctx.View(m_HDRColor))
                                .setImageLayout(vk::ImageLayout::eColorAttachmentOptimal)
-                               .setLoadOp(vk::AttachmentLoadOp::eClear)
+                               .setLoadOp(vk::AttachmentLoadOp::eLoad)
                                .setStoreOp(vk::AttachmentStoreOp::eStore)
                                .setClearValue(clearValue);
 

Engine/src/Renderer/Passes/SkyboxPass.cpp

@@ -0,0 +1,177 @@
+//
+// Created by atdunbg on 2026/9/23.
+//
+
+#include <Engine/Renderer/Passes/SkyboxPass.h>
+#include <Engine/Renderer/Cubemap.h>
+#include <Engine/Vulkan/Device.h>
+#include <Engine/Vulkan/DescriptorManager.h>
+#include <Engine/Vulkan/ShaderManager.h>
+#include <Engine/Core/Log.h>
+
+#include <glm/glm.hpp>
+
+#include <tracy/Tracy.hpp>
+
+#include <array>
+
+namespace Engine::Passes
+{
+    SkyboxPass::SkyboxPass(Device& device, ShaderManager& shaders,
+                           DescriptorManager& descriptors, FrameSceneData& frame,
+                           RG::TextureHandle hdrColor, const Cubemap* env)
+        : m_Device(device), m_Descriptors(descriptors), m_Frame(frame),
+          m_HDRColor(hdrColor), m_Env(env)
+    {
+        // Set0 = {samplerCube}（fragment 采样）
+        std::vector<DescriptorBinding> bindings = {
+            {0, vk::DescriptorType::eCombinedImageSampler,
+             vk::ShaderStageFlagBits::eFragment},
+        };
+        m_SetLayout = descriptors.CreateLayout(bindings);
+
+        // push = invVP 64B（skybox.vert/.frag 声明一致，VUID-08878）
+        m_Layout = descriptors.CreatePipelineLayout(
+            std::vector<vk::DescriptorSetLayout>{m_SetLayout},
+            sizeof(glm::mat4));
+
+        const std::string shaderDir = "shaders/";
+        auto vert = shaders.CreateFromFile(
+            shaderDir + "skybox.vert.spv",
+            vk::ShaderStageFlagBits::eVertex,
+            std::vector<vk::DescriptorSetLayout>{m_SetLayout},
+            sizeof(glm::mat4));
+        auto frag = shaders.CreateFromFile(
+            shaderDir + "skybox.frag.spv",
+            vk::ShaderStageFlagBits::eFragment,
+            std::vector<vk::DescriptorSetLayout>{m_SetLayout},
+            sizeof(glm::mat4));
+
+        m_Vert = vert.Handle;
+        m_Frag = frag.Handle;
+        if (!m_Vert || !m_Frag) {
+            ENGINE_FATAL("SkyboxPass: failed to create shader objects");
+        }
+
+        // per-slot set：cube view 全程稳定，构造期绑定一次即可
+        for (u32 slot = 0; slot < kMaxFramesInFlight; ++slot) {
+            m_Sets[slot] = descriptors.AllocateDescriptorSet(m_SetLayout);
+            if (m_Env) {
+                descriptors.UpdateTexture(m_Sets[slot], 0,
+                                          m_Env->GetSampler(),
+                                          m_Env->GetView());
+            }
+        }
+    }
+
+    SkyboxPass::~SkyboxPass()
+    {
+        const auto& vkDevice = m_Device.GetDevice();
+
+        if (m_Vert) vkDevice.destroyShaderEXT(m_Vert);
+        if (m_Frag) vkDevice.destroyShaderEXT(m_Frag);
+        vkDevice.destroyPipelineLayout(m_Layout);
+        vkDevice.destroyDescriptorSetLayout(m_SetLayout);
+    }
+
+    void SkyboxPass::Register(RG::RenderGraph& rg)
+    {
+        rg.AddPass("Skybox", [this](RG::RenderGraphContext& ctx) {
+            ZoneScopedN("Skybox");
+            const vk::CommandBuffer cmd = ctx.cmd;
+
+            vk::ClearValue clear;
+            clear.color = vk::ClearColorValue(
+                std::array<float, 4>{0.1f, 0.1f, 0.1f, 1.0f});
+
+            vk::RenderingAttachmentInfo color;
+            color.setImageView(ctx.View(m_HDRColor))
+                 .setImageLayout(vk::ImageLayout::eColorAttachmentOptimal)
+                 .setLoadOp(vk::AttachmentLoadOp::eClear)   // 清屏职责在本 pass
+                 .setStoreOp(vk::AttachmentStoreOp::eStore)
+                 .setClearValue(clear);
+
+            vk::RenderingInfo renderingInfo;
+            renderingInfo.setRenderArea({{0, 0}, ctx.extent})
+                         .setLayerCount(1)
+                         .setColorAttachments(color);   // 无深度附件
+
+            cmd.beginRendering(renderingInfo);
+
+            if (m_Env) {
+                // 无环境贴图：只清屏（Forward loadOp=Load 依赖这里先写）
+                std::array<vk::ShaderStageFlagBits, 2> stages = {
+                    vk::ShaderStageFlagBits::eVertex,
+                    vk::ShaderStageFlagBits::eFragment
+                };
+                std::array<vk::ShaderEXT, 2> shaders = {m_Vert, m_Frag};
+                cmd.bindShadersEXT(stages, shaders);
+
+                cmd.bindDescriptorSets(vk::PipelineBindPoint::eGraphics,
+                                       m_Layout, 0,
+                                       m_Sets[ctx.frame.frameSlot], {});
+                cmd.pushConstants<glm::mat4>(
+                    m_Layout,
+                    vk::ShaderStageFlagBits::eVertex |
+                    vk::ShaderStageFlagBits::eFragment,
+                    0, m_Frame.skyInvVP);
+
+                // ---- 动态状态 ----
+                cmd.setRasterizerDiscardEnable(VK_FALSE);
+
+                cmd.setDepthTestEnable(VK_FALSE);
+                cmd.setDepthWriteEnable(VK_FALSE);
+                cmd.setDepthBoundsTestEnable(VK_FALSE);
+                cmd.setStencilTestEnable(VK_FALSE);
+                cmd.setDepthBiasEnable(VK_FALSE);
+
+                cmd.setPolygonModeEXT(vk::PolygonMode::eFill);
+                cmd.setCullMode(vk::CullModeFlagBits::eNone);
+                cmd.setFrontFace(vk::FrontFace::eCounterClockwise);
+                cmd.setPrimitiveTopology(vk::PrimitiveTopology::eTriangleList);
+                cmd.setPrimitiveRestartEnable(VK_FALSE);
+
+                // 全屏三角：无顶点输入
+                cmd.setVertexInputEXT({}, {});
+
+                cmd.setRasterizationSamplesEXT(vk::SampleCountFlagBits::e1);
+                vk::SampleMask sampleMask = 0xFFFFFFFF;
+                cmd.setSampleMaskEXT(vk::SampleCountFlagBits::e1, sampleMask);
+                cmd.setAlphaToCoverageEnableEXT(VK_FALSE);
+                cmd.setAlphaToOneEnableEXT(VK_FALSE);
+
+                vk::Viewport viewport(0.0f, 0.0f,
+                                      static_cast<float>(ctx.extent.width),
+                                      static_cast<float>(ctx.extent.height),
+                                      0.0f, 1.0f);
+                cmd.setViewportWithCount(viewport);
+                cmd.setScissorWithCount(vk::Rect2D({0, 0}, ctx.extent));
+
+                // 无混合直写（天空不透明）
+                vk::ColorBlendEquationEXT blendEquation;
+                blendEquation.setSrcColorBlendFactor(vk::BlendFactor::eOne)
+                             .setDstColorBlendFactor(vk::BlendFactor::eZero)
+                             .setColorBlendOp(vk::BlendOp::eAdd)
+                             .setSrcAlphaBlendFactor(vk::BlendFactor::eOne)
+                             .setDstAlphaBlendFactor(vk::BlendFactor::eZero)
+                             .setAlphaBlendOp(vk::BlendOp::eAdd);
+                // ArrayProxyNoTemporaries 拒绝临时量：具名局部变量传入
+                vk::Bool32 blendEnable = VK_FALSE;
+                vk::ColorComponentFlags colorWriteMask =
+                    vk::ColorComponentFlagBits::eR |
+                    vk::ColorComponentFlagBits::eG |
+                    vk::ColorComponentFlagBits::eB |
+                    vk::ColorComponentFlagBits::eA;
+                cmd.setColorBlendEnableEXT(0, blendEnable);
+                cmd.setColorBlendEquationEXT(0, blendEquation);
+                cmd.setColorWriteMaskEXT(0, colorWriteMask);
+
+                cmd.draw(3, 1, 0, 0);
+            }
+
+            cmd.endRendering();
+        })
+        .Write(m_HDRColor, RG::ResourceUse::ColorAttachment);
+    }
+
+} // namespace Engine::Passes

Engine/src/Renderer/Renderer.cpp

@@ -12,8 +12,10 @@
 #include <Engine/Renderer/Passes/SceneGpu.h>
 #include <Engine/Renderer/Passes/FullscreenGpu.h>
 #include <Engine/Renderer/Passes/RenderPass.h>
+#include <Engine/Renderer/Passes/SkyboxPass.h>
 #include <Engine/Renderer/Passes/ShadowPass.h>
 #include <Engine/Renderer/Passes/ForwardPass.h>
+#include <Engine/Renderer/Cubemap.h>
 #include <Engine/Renderer/Passes/TAAPass.h>
 #include <Engine/Renderer/Passes/BloomPass.h>
 #include <Engine/Renderer/Passes/TonemapPass.h>
@@ -38,6 +40,7 @@
 #include <glm/glm.hpp>
 
 #include <array>
+#include <filesystem>
 #include <limits>
 
 namespace Engine
@@ -71,6 +74,14 @@ namespace Engine
         m_FullscreenGpu = CreateScope<Passes::FullscreenGpu>(
             *m_Device, *m_DescriptorManager, *m_ShaderManager);
 
+        // 3.5 环境贴图（IBL 阶段①）：HDR 等距柱状 → cube。
+        //     文件缺失则跳过（SkyboxPass 自动退化为纯清屏，Forward 不受影响）
+        const std::string envPath = "assets/textures/venice_dawn_1_4k.hdr";
+        if (std::filesystem::exists(envPath)) {
+            m_Environment = Cubemap::CreateFromHdrEquirect(
+                *m_Device, *m_Allocator, envPath, 1024);
+        }
+
         // 4. Swapchain（只管呈现；渲染目标统一归 RenderGraph）
         m_Swapchain = CreateScope<Swapchain>(*m_Device, *m_Allocator, m_Window);
         m_Extent = m_Swapchain->GetExtent();
@@ -228,6 +239,10 @@ namespace Engine
         FrameSceneData& frame = m_SceneRenderer->Frame();
         m_Passes.push_back(CreateScope<Passes::ShadowPass>(
             *m_SceneGpu, frame, m_ShadowMaps));
+        // Skybox = HDRColor 的 first writer（清屏 + 画背景），先于 Forward 注册
+        m_Passes.push_back(CreateScope<Passes::SkyboxPass>(
+            *m_Device, *m_ShaderManager, *m_DescriptorManager, frame,
+            m_HDRColor, m_Environment.get()));
         m_Passes.push_back(CreateScope<Passes::ForwardPass>(
             *m_SceneGpu, frame, m_HDRColor, m_Velocity, m_Depth, m_ShadowMaps));
         m_Passes.push_back(CreateScope<Passes::TAAPass>(

Engine/src/Renderer/SceneRenderer.cpp

@@ -168,6 +168,11 @@ namespace Engine
 
         ubo.ambientColor = scene.GetSettings().ambientColor;
 
+        // 天空盒：视图去平移（只留旋转）× 投影 → 逆矩阵，push 给 Skybox pass；
+        // 反投影远平面点 = 相机相对世界方向，frag normalize 后采样 cube
+        m_Frame.skyInvVP =
+            glm::inverse(ubo.projNoJitter * glm::mat4(glm::mat3(ubo.view)));
+
         // ---- 2. 灯光（第一个方向光作为 CSM 阴影光源；点光位置来自 Transform）----
         u32 lightCount = 0;
         glm::vec3 shadowDir{0.0f, -1.0f, 0.0f};   // 无灯兜底：头顶正射