Jorijn van der Graaf
852ae8abe3
DescriptorHeapVulkan - The buffer region started at images * imageDescriptorSize / bufferDescriptorSize, rounded down. A descriptor_heap array indexes the heap from byte 0 in strides of its descriptor size, so buffer slot 0 has to sit on a whole buffer descriptor past the images. Where the image descriptors were not a whole number of buffer descriptors, the first buffer descriptors overwrote the last image descriptors. Where they were less than one, the start was bumped to descriptor 1, but the heap was still sized as if the buffers began right after the images, so the last buffer descriptors went into the implementation's reserved range. Every descriptor size is a power of two, so both cases need image descriptors smaller than buffer descriptors, which NVIDIA (32 and 16 bytes) and llvmpipe (64 and 16) do not have. The start now rounds up and the heap is sized from it (#163). - The reserved range sat at a multiple of imageDescriptorAlignment only, where vkCmdBindResourceHeapEXT also wants bufferDescriptorAlignment (VUID-vkCmdBindResourceHeapEXT-pBindInfo-11435 and -11436). It now starts on a multiple of the larger. The buffer descriptors need no more than the rounding: each alignment is at most its descriptor size, so a whole number of descriptors is aligned. - bufferStartElement is 16 bits and took the division unchecked, so an image region past 65535 buffer descriptors (16384 images on llvmpipe) wrapped the buffer region around onto the images. Slot counts whose buffer indices do not fit 16 bits, 0xFFFF being the empty slot, now throw, naming the counts. A heap without buffer slots has no buffer region, which starts at 0 as in descriptor-set mode, so image-only heaps have no index to fit. - On a driver that reserves nothing (llvmpipe), a heap without sampler slots was a zero-size buffer, which every Initialize(1, 1, 0) made, and Window::Render bound its address each frame. Each heap now holds at least one descriptor, as each binding does in descriptor-set mode. That grows NVIDIA's sampler heap by one descriptor when no sampler slots are asked for; the resource heaps of the slot counts in the tree keep their layouts byte for byte. - ComputeLayout holds the arithmetic, pure over the descriptor-heap properties, and Initialize goes through it. GetBufferOffset and GetBufferOffsetElement, which had their own copies of the old arithmetic and never had a caller, are gone. - Bind(cmd, frame) binds a frame's heaps with the reserved ranges Initialize stored, or in descriptor-set mode the frame's descriptor set. Window::Render and the RTVolume example worked the reserved-range offset out from the heap's size with the image-alignment mask, and call Bind now. The window's per-heap cache of bind structs goes with it: keyed on the heap pointer, it kept binding the old buffers after a re-Initialize that reallocated them. The heap still ends with its reserved range, so code that derives the offset from the size keeps getting the right one. Tests - DescriptorHeapLayout: the issue's two layouts, the reserved range where buffer descriptors are aligned more strictly than image ones, every legal combination of descriptor sizes and alignments up to 256 bytes, no heap empty, the NVIDIA and llvmpipe layouts, the 16-bit limit and image-only heaps. Pure CPU, no device. Against the old arithmetic it fails 12 of its 18 checks. Docs - README.md's heap bullet and AGENTS.consumer.md say how to bind the heap outside the frame loop, and the consumer notes that Initialize throws when buffer indices would pass 16 bits. AGENTS.md lists ComputeLayout among the functions the pure-logic tests drive. Closes #163. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
320 lines
17 KiB
Markdown
320 lines
17 KiB
Markdown
# Crafter.Graphics
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Vulkan + WebGPU graphics library built around C++20 modules and
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bindless heaps. Provides window management, ray tracing, and a
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compute-shader-driven UI on a single, opinionated stack. Native
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builds use Vulkan with `VK_EXT_descriptor_heap` (the compute/UI path
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also runs without it, see
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[below](#drivers-without-vk_ext_descriptor_heap)); `wasm32-*` builds
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target the browser via WebGPU and a DOM window backend.
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## Backends
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Backends are chosen at build time by the target triple:
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| Target | Window | Renderer | Shaders |
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|---------------------|------------------------|---------------------|---------|
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| native Linux | Wayland | Vulkan (heap-bound) | GLSL → SPIR-V |
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| native Windows | Win32 | Vulkan (heap-bound) | GLSL → SPIR-V |
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| `wasm32-*` (any) | DOM (canvas + JS env) | WebGPU | WGSL (loaded at runtime) |
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The two backends share the same C++ surface for the high-level pieces
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(`UIRenderer`, `Mesh`, `RenderingElement3D`, `RTPass`, item structs,
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`FontAtlas`, `Image2D`, `ComputeShader`). Backend-typed pieces
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(`*Vulkan` vs `*WebGPU`) live behind `#ifdef CRAFTER_GRAPHICS_WINDOW_DOM`.
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Vulkan ray tracing is hardware (`VK_KHR_ray_tracing_pipeline`); WebGPU
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ray tracing is a library-built software path (BVH + traceRay in a
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compute pipeline composed from user-supplied WGSL stages). The WebGPU
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path supports triangle and AABB (procedural, `VK_GEOMETRY_TYPE_AABBS_KHR`)
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geometry, closest-hit / miss / any-hit / intersection shaders — see
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[examples/RTVolume](examples/RTVolume/README.md) for procedural spheres
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shaded through an intersection shader with an any-hit cut-out.
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> **Native RT status:** reading an acceleration structure through
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> `VK_EXT_descriptor_heap` aborts with `VK_ERROR_DEVICE_LOST` on NVIDIA
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> driver `610.43.02` — a driver-side fault in the brand-new descriptor-heap
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> acceleration-structure path, not an engine bug (the setup is correct and
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> validation-clean; images/buffers through the same heap work). The engine
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> **works around it transparently** (issue #15): on the NVIDIA driver only,
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> `VulkanShader` rewrites the compiled SPIR-V so heap AS reads become a
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> TLAS-device-address + `OpConvertUToAccelerationStructureKHR` path (which
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> reads no descriptor), and `RTPass` supplies the address as push data.
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> Shaders and example code are unchanged, and it's a single fenced block
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> gated on `Device::workaroundDescriptorHeapAS`, removable once a fixed
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> driver ships. **Still present on `615.78.08`**: with the rewrite off,
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> `traceRayEXT` still loses the device and an inline ray query renders
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> nothing. `tests/HeapASRead` covers the engine path; run
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> `HeapASRead --no-workaround` to check a newer driver (it tries both paths
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> with the rewrite off). Any app runs with the rewrite off while
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> `CRAFTER_GRAPHICS_NO_AS_WORKAROUND` is set, to any value. See
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> [examples/VulkanTriangle/README.md](examples/VulkanTriangle/README.md)
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> for the full investigation. WebGPU RT is unaffected.
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> **Native RT limitation (fixed in NVIDIA `615.78.08`) — dynamic
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> `descriptor_heap` indexing in hit shaders:** on NVIDIA `610.43.02`, indexing
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> a `descriptor_heap` array with a **runtime (non-constant)** index inside a
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> ray-tracing **hit** shader also device-losts (`VK_ERROR_DEVICE_LOST`), for
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> plain SSBO **and** sampled-image descriptors. On `615.78.08` it works:
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> `tests/HeapDynamicIndexHit` picks a buffer and a texture by a runtime index
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> in a closest-hit, including different descriptors in neighbouring lanes of
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> a wave. The rest of this note applies to the older drivers. A **constant / spec-constant**
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> index is fine (that's why [Sponza](examples/Sponza/README.md)'s
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> closest-hit reads `textures[albedoSlot]` and `samplers[samplerSlot]`
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> through spec constants), and
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> the identical dynamic pattern works in fragment shaders (the UI
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> renderer indexes `uiTextures[]` by per-item runtime slots) — so this
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> is **RT-stage-specific**, not a general heap problem. Unlike the
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> AS-read fault above this **cannot** be worked around transparently:
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> sampled images have no device-address escape hatch the way an
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> acceleration structure does (`OpConvertUToAccelerationStructureKHR`).
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> The recommended pattern for bindless per-mesh geometry/material is to
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> **bind one resource and index *within* it dynamically** rather than
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> selecting a descriptor dynamically: pack geometry into a single SSBO
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> (or reach it via `buffer_reference`) at a spec-constant slot and index
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> by element offset, and put materials in one `texture2DArray` indexed
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> by layer. Dynamic addressing *inside* a bound resource is ordinary
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> memory/layer addressing and is unaffected; only dynamic selection of a
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> *descriptor* faults. This is exactly what the WebGPU path already does
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> (bucketed texture arrays + a single buffer). Full investigation and
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> GLSL in [examples/Sponza/README.md](examples/Sponza/README.md) (issue
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> #23). WebGPU RT is unaffected.
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## What's in here
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- **Window** — Wayland, Win32, and DOM backends, swapchain ring / canvas
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framing, input events. Pick a backend at build time via the target
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triple. The DOM backend routes every dynamic symbol through
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[additional/dom-env.js](additional/dom-env.js) and
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[additional/dom-webgpu.js](additional/dom-webgpu.js). On Wayland the
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window needs `wl_compositor`, `wl_shm` and `xdg_wm_base`, and uses
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`xdg-decoration`, `wp_viewporter` and `wp_fractional_scale_v1` where the
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compositor has them. Without xdg-decoration (GNOME) the window has no
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title bar, as the library draws no client-side decorations; when either
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of the other two is missing it draws at scale 1, and the compositor
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scales it up on a HiDPI output.
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- **Device** *(Vulkan only)* — single-instance bring-up targeting
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`VK_EXT_descriptor_heap`; pipelines are created with
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`VK_PIPELINE_CREATE_2_DESCRIPTOR_HEAP_BIT_EXT` so there are no
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descriptor-set layouts and push constants travel via
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`vkCmdPushDataEXT`. Needs Vulkan 1.3. The heap, ray tracing and
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device-fault extensions are optional groups, detected at start-up
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(`Device::descriptorHeapSupported`, `rayTracingSupported`,
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`deviceFaultSupported`). Device features split by who uses them: the
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ones the binding model and the library's own shaders need are the
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library's to enable; arithmetic, storage and layout features an
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application's shaders use (`shaderInt16` for a `uint16_t` spec
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constant, `scalarBlockLayout`, fp16, 16-bit storage) are the
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application's to ask for, as core feature structs:
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`Device::Initialize({.vulkan10 = {.shaderInt16 = VK_TRUE}})`. A second
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argument takes features to use where the GPU has them, and
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`Device::enabledFeatures` says which it got. A GPU that can't run the
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application is skipped. `VulkanShader` refuses a module that declares,
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directly or implicitly, a capability whose core feature, subgroup
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operation or optional group (ray tracing, the descriptor heap) is off,
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naming the field to pass or saying the GPU lacks it. Capabilities only
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an extension the library never enables could allow are left to the
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driver and the validation layer, as are layout rules
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(`scalarBlockLayout`), which have no capability.
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- **DescriptorHeapVulkan / DescriptorHeapWebGPU** — bindless slot
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allocators. Vulkan side allocates image/buffer/sampler slots in a
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`VK_EXT_descriptor_heap`; WebGPU side resolves slots to JS-side
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handle-table cookies that the dispatch bridge binds per pass. The
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window binds the Vulkan heap in every frame it records; a command
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buffer recorded outside the frame loop that dispatches against it
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calls `heap.Bind(cmd, frame)`, which binds the frame's heaps, or its
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descriptor set on a driver without `VK_EXT_descriptor_heap`.
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- **VulkanBuffer\<T, Mapped\> / WebGPUBuffer\<T\>** — typed buffer.
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Vulkan variant has optional host mapping and a `FlushDevice` that
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issues the right host-write barrier; WebGPU variant goes through
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`queue.writeBuffer` over the JS bridge.
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- **ImageVulkan\<Pixel\> / Image2D\<Pixel\> / Image2DArray\<Pixel\>** —
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image + staging buffer with mip-chain support on Vulkan; on WebGPU,
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`rgba8unorm` 2D / 2D-array textures created and written via the
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bridge. Atlas (`r8unorm`, sub-region writes) is a separate path.
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- **PipelineRTVulkan / PipelineRTWebGPU / ShaderBindingTableVulkan /
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ShaderBindingTableWebGPU / RTPass** — ray-tracing pipelines. Vulkan
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uses native RT pipelines + SBTs; WebGPU compiles a **wavefront /
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streaming** software tracer — five `@compute` kernels
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(`GENERATE → PREP → TRACE → SHADE → RESOLVE`) sharing one module,
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connected by GPU ray/hit/payload buffers and a GPU-driven indirect
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bounce loop (`dispatchWorkgroupsIndirect`). TRACE carries zero user
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code (traversal + intersection only); user raygen calls
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`rtEmitPrimaryRay`, and closesthit / miss run in SHADE where they
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`rtEmitRay` continuation/shadow rays and `rtAccumulate` radiance
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(atomic — any number of rays per pixel per bounce, e.g. one shadow
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ray per light). An
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optional Resolve shader tonemaps the linear accumulator. See
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[WAVEFRONT-DESIGN.md](WAVEFRONT-DESIGN.md).
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- **ComputeShader / WebGPUComputeShader** — Tier 1 wrapper used by the
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UI system. Vulkan loads a `.spv` and dispatches with
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`vkCmdPushDataEXT` (or the `.sets.spv` build and `vkCmdPushConstants`
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without the heap); WebGPU loads a user-supplied `.wgsl` blob at
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runtime via `wgpuLoadCustomShader`. Use it directly for any custom
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compute.
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- **UI** — three-tier UI system; see below. The standard shaders (four
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kernels plus the fused one) ship as `.spv` / `.sets.spv` pairs on
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native and as WGSL strings baked into the WebGPU dispatcher.
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- **FontAtlas** — single-channel SDF atlas (1024×1024, 32pt base,
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shelf-packed, lazy `Ensure` per codepoint, dirty-flush via `Update`).
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Backend-agnostic.
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- **Mesh / RenderingElement3D / Animation** — BLAS/TLAS construction
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and 3D scene plumbing. Vulkan calls `vkCmdBuildAccelerationStructures`;
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WebGPU registers BLAS data (verts, idx, BVH nodes, primRemap, optional
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per-vertex attribs) into global mesh heaps and builds the TLAS in a
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library compute pass.
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- **Clipboard / Input / Gamepad / Router / Dom** — input plumbing.
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Gamepad uses libudev+libevdev on Linux (libevdev is vendored in
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`lib/libevdev`) and WGI on Windows; the DOM
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backend exposes the host page DOM (`Dom::HtmlElement`) and a router
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for hash-routed wasm apps.
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## UI system (three tiers)
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The UI is *deliberately* layered to balance no-boilerplate against
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no-lock-in:
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- **Tier 1 — `ComputeShader`.** Load any `.spv`, dispatch with push
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constants, library inserts inter-dispatch barriers. The escape hatch:
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if the standard shaders don't fit, write your own compute and
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dispatch it next to them.
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- **Tier 2 — `UIRenderer` + standard shaders.** Four shipped compute
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shaders (`drawQuads`, `drawCircles`, `drawImages`, `drawText`), POD
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item structs (`QuadItem`, `CircleItem`, `ImageItem`, `GlyphItem`), a
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shared GLSL contract in [shaders/ui-shared.glsl](shaders/ui-shared.glsl),
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and helpers (`RegisterBuffer`, `RegisterImage`, `RegisterSampler`,
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`FillHeader`, `Dispatch*`, `ShapeText`). You build your own per-shader
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SSBOs (manual batching) and call one `Dispatch*` per shader type per
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frame. Item array order = draw order.
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- **Tier 3 — stateless presentation functions.** `DrawButton`,
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`DrawCheckbox`, `DrawSlider`, `DrawProgressBar`. Each is a small
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function that *appends* items to your buffers — they don't dispatch.
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Colors come in as small inline `*Colors` aggregates, no library
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`Theme` type. **The source is the customization API**: if a
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component doesn't fit, copy its body and edit it. No virtual hooks,
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no extension points.
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What's *not* in the UI: widget tree, layout engine (just a `Rect::SubRect`
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carving helper), theming, hit-testing, focus management. State for
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interactive components (hover, drag, focus) lives in user-owned POD
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structs, not the library.
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### UI dispatch model
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Standard shaders dispatch one workgroup per 8×8 *screen tile* — each
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thread iterates every item in the SSBO in array order, accumulating
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into a local `dst`, and stores once. Total cost is `O(W·H·N)`; works
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well up to a few hundred items at 1080p. Splitting one buffer into
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multiple dispatches doesn't help — the same total work plus barrier
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overhead. If you need to render thousands of UI items, you want a
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different shader (tile binning, per-item-list resolve), not more
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dispatches.
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### Drivers without `VK_EXT_descriptor_heap`
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The compute/UI path also runs on Vulkan drivers that lack
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`VK_EXT_descriptor_heap` (Mesa Turnip on Qualcomm Adreno, for one).
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`Device::Initialize` detects this and sets
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`Device::descriptorHeapSupported = false`. The same slots then live in
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one bindless descriptor set per frame instead of the heap, and push
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constants go through `vkCmdPushConstants`. Slot handles, item structs,
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`UIDispatchHeader` and the `UIRenderer` API are unchanged, so
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application code does not branch on it. Ray tracing is heap-only: on
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such a driver `Device::rayTracingSupported` is false and the RT entry
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points throw.
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Each compute shader is shipped in two builds of the same source:
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`<name>.spv` for the heap and `<name>.sets.spv` for descriptor sets.
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`ComputeShader::Load(path, heap)` takes the `.spv` path and picks the
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right file itself. For a custom shader that means three things:
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- Declare bindless resources with the `UI_HEAP_*` macros from
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[shaders/ui-shared.glsl](shaders/ui-shared.glsl), not with a literal
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`descriptor_heap`:
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```glsl
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layout(UI_HEAP_BUFFERS, std430) readonly buffer MyBuf { MyItem items[]; } myHeap[];
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```
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- Register the shader twice in `project.cpp`, the second time with the
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define and the variant name:
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```cpp
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cfg.shaders.emplace_back(fs::path("my.comp.glsl"), std::string("main"), ShaderType::Compute);
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Shader& sets = cfg.shaders.emplace_back(fs::path("my.comp.glsl"), std::string("main"), ShaderType::Compute);
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sets.defines = {"CRAFTER_GRAPHICS_DESCRIPTOR_SETS"};
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sets.variant = "sets";
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```
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- Keep the push-constant block within the device's
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`maxPushConstantsSize` (256 bytes on common drivers). Without the
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heap a larger payload throws in `ComputeShader::Dispatch`.
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Set the environment variable `CRAFTER_GRAPHICS_NO_DESCRIPTOR_HEAP` to
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force the descriptor-set path on a driver that does have the heap; the
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`UIFallbackParity` test uses it to compare the two paths frame for
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frame.
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## Build
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The repository is built with `crafter-build` (a project-config based
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build system; the project description lives in `project.cpp`):
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```bash
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crafter-build # native: Wayland on Linux, Win32 on Windows
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crafter-build --target=wasm32-wasip1 # browser: DOM window + WebGPU renderer
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crafter-build -r # build and run (in an example directory)
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```
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The build picks the window + renderer pair automatically from the
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target triple: any `wasm32-*` triple flips to DOM + WebGPU (no Vulkan
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loader linked), everything else stays on the native Vulkan path. Each
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example with both backends ships GLSL *and* WGSL copies of its shaders
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side-by-side (e.g. [raygen.glsl](examples/Sponza/raygen.glsl) +
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[raygen.wgsl](examples/Sponza/raygen.wgsl)); `project.cpp` selects the
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right set per target.
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## Examples
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See [examples/](examples/). Quick map:
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- [HelloWindow](examples/HelloWindow/) — minimal native window, no rendering.
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- [HelloDom](examples/HelloDom/) — wasm-only smoke test of the DOM
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partition: page-level events, `HtmlElement::CreateInBody`, and
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`Router::PushState`-driven SPA navigation. No GPU work.
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- [VulkanTriangle](examples/VulkanTriangle/) — ray-traced triangle on
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both Vulkan and WebGPU. The smallest test of the bindless + RT path
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on each backend.
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- [RTStress](examples/RTStress/) — wavefront RT benchmark: an N×N×N grid
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of a cube mesh (instance-count knob `kGrid`, 512 → 8000) shaded with
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primary + shadow rays. Prints a GPU timestamp-query per-pass breakdown
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each second. WebGPU/DOM only.
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- [Sponza](examples/Sponza/) — ray-traced Sponza atrium on both
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backends. Exercises `.cmesh` / `.ctex` decompression (GPU
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`VK_EXT_memory_decompression` on Vulkan, CPU on WebGPU) and a
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textured closest-hit. See [its README](examples/Sponza/README.md)
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for asset provenance.
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- [HelloUI](examples/HelloUI/) — UI smoke test using all three tiers
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(background quad, slider, progress bar, button with text label,
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cursor-tracking circle).
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- [CustomShader](examples/CustomShader/) — Tier 1 demo: a user-authored
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compute shader inverting RGB under a list of item-circles, dispatched
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alongside the standard `drawQuads`. Shipped as both
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[`.comp.glsl`](examples/CustomShader/inverse-circle.comp.glsl) and
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[`.comp.wgsl`](examples/CustomShader/inverse-circle.comp.wgsl).
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- [Decompression](examples/Decompression/) — `Crafter::Compression`
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CPU round-trip smoke test (used by the WebGPU asset path).
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- [InputSystem](examples/InputSystem/) — keyboard / mouse / gamepad
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event surface check.
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## License
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This library is licensed under the GNU Lesser General Public License, version 3 only (LGPL-3.0-only). See [LICENSE](LICENSE) for the license text. The LGPL supplements the GNU General Public License version 3, a copy of which is included as [LICENSE.GPL](LICENSE.GPL).
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The example code under [examples/](examples/) is licensed under the MIT license (see [examples/LICENSE](examples/LICENSE)), so it can be freely copied into your own projects.
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The [lib/](lib/) directory contains vendored third-party code (stb, Wayland protocol bindings) that remains under its own permissive licenses; see the headers of those files.
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## Copyright
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||
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Copyright (C) 2026 Catcrafts®
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catcrafts.net
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