FluidCAD-from-drawing

Modeling a part from a drawing

This skill layers on top of the FluidCAD skill. That one owns everything generic: the MCP loop (read the docs, write the file, check render.state, screenshot), parallel doc research with sub-agents, what a build plan contains and how to write it, building in small increments, when a feature earns a verification screenshot, and rolling the scene back to debug. Follow it. This skill covers only what is specific to working from a drawing: reading it correctly, turning it into that plan, and checking the result back against the sheet.

The governing principle: a drawing is a specification you are transcribing, not a picture you are approximating. Every number in the model should trace back to a number on the sheet.

1. Every read of the drawing is whole — no cropping, ever

Open the drawing with whatever file/image reading tool your client provides — and for a multi-page PDF, read every page, not just the first.

Whoever reads the sheet reads the original image, whole — you and every transcriber alike. Do not crop it, tile it into quadrants, split out a region, zoom-and-slice, or otherwise preprocess it into sub-images to pull the dimensions out. It feels like it should help; it does not:

• Cropping strips the context that gives a number its meaning. A dimension is defined by the extension lines it spans, the arrowheads at its ends, and the view it sits in. Isolated in a tile, 24 is just a number with no referent — and that is exactly how a width gets modeled as a depth.
• Splitting causes both double-counting and omission. The same dimension shows up in two tiles and gets modeled twice, or it lands on a seam and vanishes from both. Neither failure announces itself.
• Re-encoding adds no information. Enlarging a blurry region does not recover pixels the original never had; it produces confident-looking digits that were never on the sheet. A misread you invented this way is indistinguishable from a real reading.