Showcase Tuning: A Visual Debugging Workflow for AI-Assisted Rendering Code

Rendering code has a testing problem that most developers quietly accept: you can write all the unit tests you want, but none of them tell you whether the output actually looks right . Unit tests verify logic. They can't catch inverted normals, clipped sprites, washed-out colors, or a balloon shape that looks like a UFO. So I built a workflow called Showcase Tuning to solve this - and packaged it as a Claude Code skill so AI can run the entire loop autonomously. The Core Idea The workflow is a tight loop: Write a harness → Run it → Look at what came out → Fix the renderer → Repeat The harness is a small, standalone program that calls your actual rendering code with deterministic inputs and saves the output as a PNG. It's not a mock or reimplementation - it's a camera pointed at your real code. A few rules keep the loop honest: Deterministic inputs - fixed seeds and hardcoded data so every run is comparable Fix the renderer, not the harness - the harness is just a capture mechanism; def