Tag

webgpu

9 posts

rendering

7 min read Jul 15, 2026

Draped at the wrong tile: a deferred write turned a shared uniform pool into a data race

A draped landcover polygon rendered hundreds of kilometres offshore — but only on WebGPU. Every vector slice of one source shares one Material uniform pool, and each slice resets the pool cursor to 0, so a later slice's tile i overwrote an earlier slice's tile-i buffer. WebGPU's queue.writeBuffer defers to submit (last-writer-wins), so every draw read the final bytes; WebGL2's immediate bufferSubData never showed it — and the differential test was structurally blind, because both frames aliased identically.

webgpu debugging globe

testing

5 min read Jul 11, 2026

The pixel test that passed on the wrong GPU

The same render test passed twice: once at 38.5% painted pixels on real WebGPU, once at 93.6% on a silent WebGL2 fallback the assertion never noticed. Why a designed-in fallback chain turns every green output test ambiguous — until the test also pins which backend produced the frame.

webgpu playwright e2e

webgpu

7 min read Jul 8, 2026

The unused binding that silently dropped the draw

A shader drew correctly on one GPU and returned the clear colour on another — not precision, but layout:auto deleting a binding it declared but never read. When an interface is derived from usage, an unused declaration is a mismatch only the strict backend reveals.

graphics api-design debugging

rhi

7 min read Jul 8, 2026

Swapping the command encoder without stopping the frame

Moving map's render passes behind the RHI one at a time meant two encoders — native and RHI — had to share a single frame and a single submit. Why createCommandEncoder was the wrong tool, and the wrapper that let a native encoder be driven through the RHI interface for one pass at a time.

architecture webgpu refactoring

shader-dsl

6 min read Jul 8, 2026

Your bundler minifies everything except your shaders

Emitted WGSL/GLSL ships to gl.shaderSource with its authored vocabulary intact — no JS minifier reaches it. A Vite/Webpack-style emit-plugin pass (mangle + minify) that compacts and obfuscates the shader text, the ABI boundary it must never cross, and why compile-and-link is not enough to trust it.

compiler tooling webgpu

shader-dsl

6 min read Jul 7, 2026

Emulated double precision in the shader DSL

f64 and vecN<f64> as first-class shader-dsl types, emulated as two-f32 double-float pairs — same authoring syntax as f32, one lowering pass, ~48 significand bits.

precision compiler webgpu

testing

4 min read Jul 7, 2026

What a software GPU can and cannot verify

Our CI runs real shaders on SwiftShader — but only some render claims survive a CPU rasterizer. The dividing line we use (compute parity and shader compilation: yes; full-pipeline pixel parity: no), and the red-baseline incident that taught us to blame the software GPU last.

ci webgpu gpu-drivers

compiler

6 min read Jul 7, 2026

The .xgis compiler pipeline: from style text to GPU programs

How a declarative map style becomes GPU work: lexer → parser → a Scene IR → optimization passes → codegen that emits typed shader-dsl IR (never WGSL strings), per-feature compute kernels for match(), and a gradient atlas for zoom-dependent paint.

engine webgpu shader-dsl

engine

2 min read Jun 26, 2026

Why we built a GPU-first map engine

X-GIS compiles a declarative style language into optimized WebGPU shaders — through a real compiler and a typed shader IR. Here's the shape of the system and why each layer exists.

webgpu compiler intro