glslViewer Shader Debug

Use this skill to turn shader math into repeatable headless previews.

Workflow

1. Confirm glslViewer is available with command -v glslViewer || command -v glslviewer.
2. Create a scratch .frag file, usually by copying assets/sdf-contour-template.frag.
3. Translate the source shader into standard GLSL.
4. Render the shader with scripts/render_headless.sh.
5. Inspect the generated PNGs and compare the contour or mask shape against expectations.

Translation Rules

• For runtime-shader or SkSL-like snippets, read references/runtime-effect-to-glsl.md.
• Keep the math identical first. Change syntax before changing behavior.
• Replace non-standard types such as half4 or float2 with GLSL equivalents.
• Rewrite main(vec2 fragCoord) into standard fragment entrypoint form: