Shard

Shard is a CLI program for offscreen rendering WGSL pixel (fragment) shaders into images (PNG) or animations (GIF).

Shard can be considered as alternative to Shadertoy and similar projects, but for local image and animation generation.

Goals:

• Write only shader code - no C/C++/Rust/JS/... wrappers for rendering
• Single-file specification due to WGSL
• Reproducible - ability to integrate with reproducible research instruments like Jupyter, R Markdown, or your notes/articles writing system
• Only one, small and working fast (~13 MB) binary file without external dependencies and footprint
• Cross-platform

Installation

Shard can be installed using Cargo.

cargo install shard\
  --index sparse+https://gitea.zarux.ru/api/packages/deverte/cargo/

First steps

Write WGSL shader wave.wgsl:

@group(0) @binding(0) var<uniform> in_res: vec2<u32>;
@group(0) @binding(1) var<uniform> in_frame: u32;

const FRAMES = 10.0;

@vertex
fn vs_main(
    @builtin(vertex_index) in_vertex_index: u32,
) -> @builtin(position) vec4<f32> {
    var vertices = array<vec4<f32>, 6>(
        vec4<f32>(-1.0, 1.0, 0.0, 1.0),
        vec4<f32>(1.0, 1.0, 0.0, 1.0),
        vec4<f32>(-1.0, -1.0, 0.0, 1.0),
        vec4<f32>(1.0, 1.0, 0.0, 1.0),
        vec4<f32>(-1.0, -1.0, 0.0, 1.0),
        vec4<f32>(1.0, -1.0, 0.0, 1.0),
    );
    return vertices[in_vertex_index];
}

fn palette(
    t: f32, a: vec3<f32>,
    b: vec3<f32>,
    c: vec3<f32>,
    d: vec3<f32>,
) -> vec3<f32> {
    return a + b * abs(cos(6.28318 * (c * t + d)));
}

fn ocean(t: f32) -> vec3<f32> {
    let a = vec3<f32>(0.0, 0.5, 0.5);
    let b = vec3<f32>(0.1, 0.3, 0.5);
    let c = vec3<f32>(0.0, 0.5, 0.333);
    let d = vec3<f32>(0.0, 0.5, 0.667);
    return palette(t, a, b, c, d);
}

@fragment
fn fs_main(
    @builtin(position) in_pos: vec4<f32>,
) -> @location(0) vec4<f32> {
    let uv = in_pos.xy / vec2(f32(in_res.x), f32(in_res.y));
    let step = 3.14159 / FRAMES;
    return vec4<f32>(ocean(uv.x * 4 * sin(f32(in_frame) * step)), 1.0);
}

Compile:

shard wave.wgsl -f 10 -x 128 -y 128 -o wave.gif

Result:

Documentation

CLI

Usage: shard [OPTIONS] <INPUT>

Arguments:

• <INPUT> - Input WGSL (.wgsl) fragment (pixel) shader

Options:

• -o, --output <OUTPUT> - Output file (with .png or .gif extension) [default: image.png]
• -x, --width <WIDTH> - Image width (must be multiple of [256 / 4]) [default: 512]
• -y, --height <HEIGHT> - Image height [default: 512]
• -f, --frames-count <FRAMES_COUNT> - Number of frames (for GIF output) [default: 60]
• -h, --help - Print help
• -v, --version - Print version

Shader

Shard provides two uniforms for fragment shader:

• @group(0) @binding(0) var<uniform> in_res: vec2<u32>; - screen resolution
• @group(0) @binding(1) var<uniform> in_frame: u32; - frame number (for GIF)

License

• License: GPL-3
• Author: Artem Shepelin