RenderAttachmentLayout是Atom中定义渲染附件信息的数据，vulkan中RenderPass和SubPass的创建需要此数据。DX12不会使用这个数据（除了RTV格式），它的”渲染附件“是在记录命令时动态绑定的，也没有RenderPass和SubPass这个概念。
结构体层级与关系
RenderAttachmentConfiguration（配置：用哪个 subpass）
└── RenderAttachmentLayout（整个 render pass 的布局）
├── m_attachmentFormats[] → 所有附件的格式
└── m_subpassLayouts[] → 每个 subpass 的布局
└── SubpassRenderAttachmentLayout（单个 subpass）
├── m_rendertargetDescriptors[] → RenderAttachmentDescriptor[]
├── m_subpassInputDescriptors[] → SubpassInputDescriptor[]
├── m_depthStencilDescriptor → RenderAttachmentDescriptor
└── m_shadingRateDescriptor → RenderAttachmentDescriptor
RenderAttachmentDescriptor
//! Describes one render attachment that is part of a layout.
struct ATOM_RHI_REFLECT_API RenderAttachmentDescriptor
{
AZ_TYPE_INFO(RenderAttachmentDescriptor, "{2855E1D2-BDA1-45A8-ABB9-5D8FB1E78EF4}");
static void Reflect(ReflectContext* context);
bool IsValid() const;
bool operator==(const RenderAttachmentDescriptor& other) const;
bool operator!=(const RenderAttachmentDescriptor& other) const;
bool IsEqual(const RenderAttachmentDescriptor& other, const bool compareLoadStoreAction) const;
//! Position of the attachment in the layout.
uint32_t m_attachmentIndex = InvalidRenderAttachmentIndex;
//! Position of the resolve attachment in layout (if it resolves).
uint32_t m_resolveAttachmentIndex = InvalidRenderAttachmentIndex;
//! Load and store action of the attachment.
AttachmentLoadStoreAction m_loadStoreAction = AttachmentLoadStoreAction();
//! The following two flags are only relevant when there are more than one subpasses
//! that will be merged.
//! The scope attachment access as defined in the pass template, which will be used
//! to accurately define the subpass dependencies.
AZ::RHI::ScopeAttachmentAccess m_scopeAttachmentAccess = AZ::RHI::ScopeAttachmentAccess::Unknown;
//! The scope attachment stage as defined in the pass template, which will be used
//! to accurately define the subpass dependencies.
AZ::RHI::ScopeAttachmentStage m_scopeAttachmentStage = AZ::RHI::ScopeAttachmentStage::Uninitialized;
//! Extra data that can be passed for platform specific operations.
RenderAttachmentExtras* m_extras = nullptr;
};描述一个附件在某个 subpass 中的用法（颜色/深度/解析/着色率等）。
| 成员 | 含义 | Vulkan 大致对应 |
|---|---|---|
m_attachmentIndex | 该附件在全局附件列表中的索引 | VkAttachmentReference.attachment |
m_resolveAttachmentIndex | 解析目标附件索引（MSAA resolve） | VkSubpassDescription.pResolveAttachments[] 中的 attachment index |
m_loadStoreAction | Load/Store 行为 | VkAttachmentDescription.loadOp/storeOp（以及 stencil） |
m_scopeAttachmentAccess | 读/写访问 | 用于推导 VkSubpassDependency 的 srcAccessMask/dstAccessMask |
m_scopeAttachmentStage | 使用阶段 | 用于推导 VkSubpassDependency 的 srcStageMask/dstStageMask |
m_extras | 平台扩展 | 可映射到 Vulkan 扩展结构 |
SubpassInputDescriptor
//! Describes a subpass input attachment.
struct ATOM_RHI_REFLECT_API SubpassInputDescriptor
{
AZ_TYPE_INFO(SubpassInputDescriptor, "{5E5B933D-8209-4722-8AC5-C3FEA1D75BB3}");
static void Reflect(ReflectContext* context);
bool operator==(const SubpassInputDescriptor& other) const;
bool operator!=(const SubpassInputDescriptor& other) const;
//! Attachment index that this subpass input references.
uint32_t m_attachmentIndex = 0;
//! Aspects that are used by the input (needed by some implementations, like Vulkan, when creating a renderpass with a subpass input)
RHI::ImageAspectFlags m_aspectFlags = RHI::ImageAspectFlags::None;
//! The following two flags are only relevant when there are more than one subpasses
//! that will be merged.
//! The scope attachment access as defined in the pass template, which will be used
//! to accurately define the subpass dependencies.
AZ::RHI::ScopeAttachmentAccess m_scopeAttachmentAccess = AZ::RHI::ScopeAttachmentAccess::Unknown;
//! The scope attachment stage as defined in the pass template, which will be used
//! to accurately define the subpass dependencies.
AZ::RHI::ScopeAttachmentStage m_scopeAttachmentStage = AZ::RHI::ScopeAttachmentStage::Uninitialized;
//! Load and store action of the attachment.
AttachmentLoadStoreAction m_loadStoreAction = AttachmentLoadStoreAction();
//! Extra data that can be passed for platform specific operations.
RenderAttachmentExtras* m_extras = nullptr;
};描述本 subpass 内以“input attachment”方式引用的附件（只读，通常用于同一 render pass 内前一 subpass 的输出）。
| 成员 | 含义 | Vulkan 大致对应 |
|---|---|---|
m_attachmentIndex | 引用的附件在全局列表中的索引 | VkAttachmentReference.attachment（在 pInputAttachments 中） |
m_aspectFlags | 使用的 image aspect | VkAttachmentReference.aspectMask（Vulkan 创建带 input attachment 的 render pass 时需要） |
m_scopeAttachmentAccess/Stage | 访问与阶段 | 用于 subpass dependency 的 access/stage mask |
m_loadStoreAction | Load/Store | 对应该附件的 load/store |
m_extras | 平台扩展 | 同上 |
SubpassRenderAttachmentLayout
描述一个 subpass 用到的所有附件种类和数量。
//! Describes the attachments of one subpass as part of a render target layout.
//! It include descriptions about the render targets, subpass inputs and depth/stencil attachment.
struct ATOM_RHI_REFLECT_API SubpassRenderAttachmentLayout
{
AZ_TYPE_INFO(SubpassRenderAttachmentLayout, "{7AF04EC1-D835-4F97-8433-0D445C0D6F5B}");
static void Reflect(ReflectContext* context);
bool operator==(const SubpassRenderAttachmentLayout& other) const;
bool operator!=(const SubpassRenderAttachmentLayout& other) const;
bool IsEqual(const SubpassRenderAttachmentLayout& other, const bool compareLoadStoreAction) const;
//! Number of render targets in the subpass.
uint32_t m_rendertargetCount = 0;
//! Number of subpass input attachments in the subpass.
uint32_t m_subpassInputCount = 0;
//! List of render targets used by the subpass.
AZStd::array<RenderAttachmentDescriptor, Limits::Pipeline::AttachmentColorCountMax> m_rendertargetDescriptors = { {} };
//! List of subpass inputs used by the subpass.
AZStd::array<SubpassInputDescriptor, Limits::Pipeline::AttachmentColorCountMax> m_subpassInputDescriptors = { {} };
//! Descriptor of the depth/stencil attachment. If not used, the attachment index is InvalidRenderAttachmentIndex.
RenderAttachmentDescriptor m_depthStencilDescriptor;
//! Descriptor of the shading rate attachment. If not used, the attachment index is InvalidRenderAttachmentIndex.
RenderAttachmentDescriptor m_shadingRateDescriptor;
};| 成员 | 含义 | Vulkan 大致对应 |
|---|---|---|
m_rendertargetCount | 颜色附件数量 | VkSubpassDescription.colorAttachmentCount |
m_rendertargetDescriptors | 颜色（及 resolve）附件 | pColorAttachments / pResolveAttachments |
m_subpassInputCount | Input 附件数量 | inputAttachmentCount |
m_subpassInputDescriptors | Input 附件 | pInputAttachments |
m_depthStencilDescriptor | 深度/模板 | pDepthStencilAttachment |
m_shadingRateDescriptor | 着色率附件 | VK_KHR_fragment_shading_rate 的 attachment |
用途：对应 VkSubpassDescription（不含 dependency，dependency 由 access/stage 等信息在别处推导）。
RenderAttachmentLayout（整个 Render Pass 的布局）
描述整个 render pass：有多少个附件、每个附件的格式、有多少个 subpass、每个 subpass 的布局。
//! A RenderAttachmentLayout consist of a description of one or more subpasses.
//! Each subpass is a collection of render targets, subpass inputs and depth stencil attachments.
//! Each subpass corresponds to a phase in the rendering of a Pipeline.
//! Subpass outputs can be read by other subpasses as inputs.
//! A RenderAttachmentLayout may be implemented by the platform using native functionality, achieving a
//! performance gain for that specific platform. On other platforms, it may be emulated to achieve the same result
//! but without the performance benefits. For example, Vulkan supports the concept of subpass natively.
class ATOM_RHI_REFLECT_API RenderAttachmentLayout
{
public:
AZ_TYPE_INFO(RenderAttachmentLayout, "{5ED96982-BFB0-4EFF-ABBE-1552CECE707D}");
static void Reflect(ReflectContext* context);
HashValue64 GetHash() const;
bool operator==(const RenderAttachmentLayout& other) const;
bool IsEqual(const RenderAttachmentLayout& other, const bool compareLoadStoreAction) const;
//! Number of total attachments in the list.
uint32_t m_attachmentCount = 0;
//! List with all attachments (renderAttachments, resolveAttachments and depth/stencil attachment).
AZStd::array<Format, Limits::Pipeline::RenderAttachmentCountMax> m_attachmentFormats = { {} };
//! Number of subpasses.
uint32_t m_subpassCount = 0;
//! List with the layout of each subpass.
AZStd::array<SubpassRenderAttachmentLayout, Limits::Pipeline::SubpassCountMax> m_subpassLayouts;
};| 成员 | 含义 | Vulkan 大致对应 |
|---|---|---|
m_attachmentCount | 附件总数 | VkRenderPassCreateInfo.attachmentCount |
m_attachmentFormats | 每个附件的格式 | VkAttachmentDescription[].format（其他 loadOp/storeOp 等可从各 subpass 的 descriptor 汇总） |
m_subpassCount | Subpass 数量 | VkRenderPassCreateInfo.subpassCount |
m_subpassLayouts | 每个 subpass 的布局 | VkRenderPassCreateInfo.pSubpasses → 每个 VkSubpassDescription |
用途：对应 VkRenderPassCreateInfo 的主干数据（attachment 列表 + subpass 数组）。
RenderAttachmentConfiguration（“当前用哪个 Subpass”的配置）
在已有 RenderAttachmentLayout（可能包含多个 subpass）的基础上，表示当前管线/Pass 实际使用的是哪一个 subpass，并对外提供该 subpass 的格式、数量等查询接口。
//! Describes the layout of a collection of subpasses and it defines which of the subpasses this
//! configuration will be using.
struct ATOM_RHI_REFLECT_API RenderAttachmentConfiguration
{
AZ_TYPE_INFO(RenderAttachmentConfiguration, "{037F27A5-B568-439B-81D4-928DFA3A74F2}");
static void Reflect(ReflectContext* context);
HashValue64 GetHash() const;
bool operator==(const RenderAttachmentConfiguration& other) const;
bool IsEqual(const RenderAttachmentConfiguration& other, const bool compareLoadStoreAction) const;
//! Returns the format of a render target in the subpass being used.
Format GetRenderTargetFormat(uint32_t index) const;
//! Returns the format of a subpass input in the subpass being used.
Format GetSubpassInputFormat(uint32_t index) const;
//! Returns the format of resolve attachment in the subpass being used.
Format GetRenderTargetResolveFormat(uint32_t index) const;
//! Returns the format of a depth/stencil in the subpass being used.
//! Will return Format::Unkwon if the depth/stencil is not being used.
Format GetDepthStencilFormat() const;
//! Returns the number of render targets in the subpass being used.
uint32_t GetRenderTargetCount() const;
//! Returns the number of subpass inputs in the subpass being used.
uint32_t GetSubpassInputCount() const;
//! Returns true if the render target is resolving in the subpass being used.
bool DoesRenderTargetResolve(uint32_t index) const;
//! Layout of the render target attachments.
RenderAttachmentLayout m_renderAttachmentLayout;
//! Index of the subpass being used.
uint32_t m_subpassIndex = 0;
};| 成员 | 含义 | Vulkan 对应 |
|---|---|---|
m_renderAttachmentLayout | 完整 render pass 布局 | 同上，用于创建 VkRenderPass |
m_subpassIndex | 当前使用的 subpass 索引 | 创建 VkGraphicsPipeline 时传入的 subpass 索引 |
GetRenderTargetFormat、GetDepthStencilFormat、GetRenderTargetCount 等接口都是针对 m_subpassLayouts[m_subpassIndex] 的便捷访问，便于管线和 framebuffer 绑定阶段使用。