Buffers are required to build acceleration structures

Error message

Buffers are required to build acceleration structures

What it means

When building acceleration structures (Vulkan ray tracing), wgpu-hal needs the device address of the source buffer holding the build geometry data. If the buffer reference is `None` at this point, the backend panics, because a build command without an underlying buffer cannot produce the required `vk::AccelerationStructureBuildGeometryInfoKHR` device addresses. In normal operation wgpu-core always supplies a buffer; hitting this indicates the internal invariant was broken.

Source

Thrown at wgpu-hal/src/vulkan/command.rs:587

        const CAPACITY_OUTER: usize = 8;
        const CAPACITY_INNER: usize = 1;
        let descriptor_count = descriptor_count as usize;

        let ray_tracing_functions = self
            .device
            .extension_fns
            .ray_tracing
            .as_ref()
            .expect("Feature `RAY_TRACING` not enabled");

        let get_device_address = |buffer: Option<&super::Buffer>| unsafe {
            match buffer {
                Some(buffer) => ray_tracing_functions
                    .buffer_device_address
                    .get_buffer_device_address(
                        &vk::BufferDeviceAddressInfo::default().buffer(buffer.raw),
                    ),
                None => panic!("Buffers are required to build acceleration structures"),
            }
        };

        // storage to all the data required for cmd_build_acceleration_structures
        let mut ranges_storage = smallvec::SmallVec::<
            [smallvec::SmallVec<[vk::AccelerationStructureBuildRangeInfoKHR; CAPACITY_INNER]>;
                CAPACITY_OUTER],
        >::with_capacity(descriptor_count);
        let mut geometries_storage = smallvec::SmallVec::<
            [smallvec::SmallVec<[vk::AccelerationStructureGeometryKHR; CAPACITY_INNER]>;
                CAPACITY_OUTER],
        >::with_capacity(descriptor_count);

        // pointers to all the data required for cmd_build_acceleration_structures
        let mut geometry_infos = smallvec::SmallVec::<
            [vk::AccelerationStructureBuildGeometryInfoKHR; CAPACITY_OUTER],
        >::with_capacity(descriptor_count);
        let mut ranges_ptrs = smallvec::SmallVec::<

View on GitHub (pinned to 3e11ff59bf)

Solutions

Ensure every acceleration structure build descriptor has a valid, live buffer before calling build_acceleration_structures
Hold the buffer (keep the wgpu::Buffer/Arc alive) until the build has been submitted and completed
Update wgpu — this may be an internal lifetime bug; report with a backtrace if reproducible with standard wgpu APIs
If using wgpu-hal directly, pass Some(buffer) with correct usage ACCELERATION_STRUCTURE_BUILD_INPUT_READ_ONLY

Example fix

// before
encoder.build_acceleration_structures(&[BuildAccelerationStructureDescriptor { buffer: None, .. }]);
// after
let blas_buffer = device.create_buffer(&BufferDescriptor { usage: BufferUses::ACCELERATION_STRUCTURE_BUILD_INPUT_READ_ONLY, .. });
encoder.build_acceleration_structures(&[BuildAccelerationStructureDescriptor { buffer: Some(&blas_buffer), .. }]);

Defensive patterns

Strategy: validation

Validate before calling

assert!(blas_buffer.is_some(), "acceleration structure build requires a buffer");

Try / catch

std::panic::catch_unwind(|| encoder.build_acceleration_structures(&descs))

Prevention

Keep buffers alive until build submission completes
Always attach a buffer to every BuildAccelerationStructureDescriptor
Validate ray-tracing descriptors before encoding

When it happens

Trigger: Invoking `command_encoder.build_acceleration_structures` on the Vulkan backend where an entry in the build descriptors has no acceleration structure buffer backing it — e.g. a descriptor whose buffer was dropped, never set, or built by an internal caller passing `None` as the buffer.

Common situations: Using experimental ray-tracing APIs or internal wgpu-hal APIs directly; a wgpu-core/HAL desynchronization bug where buffer lifetime management dropped the buffer before the build; custom engines integrating wgpu-hal Vulkan ray tracing by hand.

Related errors

AI-assisted analysis of gfx-rs/wgpu@3e11ff59bf (2026-09-03). Data as JSON: /api/errors/b9827a105d323b2b. Report an issue: GitHub.