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Qaws (قوس) — Arabic for arc, bow, curve. A dependency-free C11 library for creating, evaluating, sampling, traversing, and inspecting parametric curves and surfaces in 2D and 3D.

One source, four backends: C · HLSL · GLSL · Halide

#include "qaws.h"

qaws_vec2 pts[] = { {0,0}, {0.3f,1}, {0.7f,1}, {1,0} };
qaws_bezier_desc desc = {
    .dimension = QAWS_DIMENSION_2D,
    .degree = 3,
    .control_points = pts,
    .control_point_count = 4
};

qaws_curve* curve = NULL;
qaws_curve_create_bezier(&desc, &curve);

qaws_eval_result_2d r;
qaws_curve_evaluate_2d(curve, 0.5f, QAWS_EVAL_FLAG_POSITION | QAWS_EVAL_FLAG_D1, &r);
// r.position = point on curve at t=0.5
// r.d1       = first derivative (tangent direction)

qaws_curve_destroy(curve);

Every family is created through a descriptor and shares the same evaluation, sampling, traversal, and inspection API after creation.

13 curve families + 5 surface types. See the curve families table above.

The core evaluation math lives in header-only files under src/qaws/core/. These compile on all four backends from the same source:

// HLSL compute shader
#include "qaws_hlsl.h"
#include "core/qaws_decasteljau_core.h"

[numthreads(256, 1, 1)]
void CSMain(uint3 id : SV_DispatchThreadID) {
    float t = (float)id.x / (float)(sample_count - 1);
    qaws_vec2 pos = qaws_bezier3_eval_2d(p0, p1, p2, p3, t);
    results[id.x * 2]     = pos.x;
    results[id.x * 2 + 1] = pos.y;
}

Backend detection is automatic (__HLSL_VERSION, GL_core_profile, HALIDE_HALIDERUNTIME_H) or forced via bootstrap headers (qaws_hlsl.h, qaws_glsl.h, qaws_halide.h).

Sharpmake (primary) or CMake (backup).

# CMake
cmake -B build -DQAWS_SCALAR_IS_FLOAT=ON
cmake --build build --config Release
ctest --build-config Release --output-on-failure

# Sharpmake
sharpmake /sources(@'buildsystem/sharpmake/src/main.sharpmake.cs')

• Zero dependencies -- C11 standard library only (<math.h>, <stdlib.h>, <string.h>)
• Immutable after creation -- qaws_curve and qaws_surface are thread-safe for concurrent reads
• Opaque handles -- all internal state is hidden behind qaws_curve* / qaws_surface*
• Status codes everywhere -- every fallible function returns qaws_status
• Custom allocators -- _ex variants accept qaws_allocator for arena/pool/tracking
• Stack-allocated curves -- qaws_curve_inline for hot paths (no malloc, degree <= 7)

src/qaws/            Public headers and C implementation
src/qaws/core/       Header-only eval kernels (all backends)
src/qaws/internal/   Private implementation details
src/qaws/simd/       SIMD abstraction (AVX2, SSE2, NEON, scalar)
src/qaws/batch/      SIMD batch evaluation
tests/               Test runner
examples/            HLSL, GLSL, Halide shader examples
docs/                Documentation
buildsystem/         Sharpmake project files

Full docs are in docs/:

• Overview -- design principles, quick start
• Backends -- C / HLSL / GLSL / Halide architecture
• Curve Families -- all 13 families in detail
• Evaluation -- eval flags, batch eval, core headers, prepare+eval
• Sampling -- uniform, adaptive, curvature-weighted, streaming
• Traversal -- motion profiles, easing, wrap modes
• Inspection -- geometry queries, intersection, analysis
• Building -- CMake and Sharpmake configuration
• Feature Matrix -- function-by-function backend support

See LICENSE.