dsh-cad-preview: View Real CAD 3D Models in the DeepSeek Harness Sidebar

What Does It Do?

It is a DSH plugin for DeepSeek Harness that turns the sidebar file tree into a 3D viewer for real CAD geometry you can orbit, zoom and inspect. It solves the problem of opening STEP, IGES or BREP files inside DSH and seeing only text, letting you verify part shapes and dimensions right next to the chat. It parses both B-rep and mesh formats and reports bounding-box size, triangle count and parse time.

Core Features

• Multi-format parsing: .step / .stp / .iges / .igs / .brep go through OpenCascade WASM for true B-rep tessellation, while .stl / .3mf / .obj / .ply use mesh loaders.
• Off-main-thread parsing: B-rep work runs in a Web Worker, so the page bundle carries no kernel and heavy models cannot freeze the whole DSH interface or crash the renderer.
• Interactive camera: left-drag to orbit, right-drag or Shift plus left-drag to pan, wheel to zoom, with toolbar actions for wireframe, Z/Y up, grid, fit and reset.
• Structural edges and wireframe: the default look combines ambient occlusion with 30° structural edges, while wireframe hides faces and keeps 1° edges so cylinder sides stay visible.
• Axis gizmo: three colored lettered arrows in the lower right rotate with the view to show the model coordinate system without blocking pointer input.
• Normal fallback: missing, mismatched, all-zero or NaN normals are derived from faces, preventing models from rendering completely black.

How to Use This Plugin?

After enabling it in DSH, open a CAD file from the sidebar file tree and the viewer tessellates it into triangles and renders it with WebGL. The top bar shows file size, bounding-box dimensions, triangle count and parse time so you can tell whether the model loaded fully. Drag or scroll to change the view, press the wireframe button to inspect internal structure, and use fit to reframe the model. It works with dsh-better-sidebar or the built-in document preview, is maintained by RichardYZLu, and was last updated on 2026-10-08.

How to Troubleshoot This Plugin?

A model rendering completely black is usually not a viewer defect but an STL file whose facet normals are all zero; the plugin applies a usable-normal fallback and keeps valid normals untouched. If heavy models make the interface stutter or the renderer misbehave, parsing is not running on its own thread, so follow the official notes to confirm the Worker path is active. Flickering seams at architectural scale come from a fixed near/far clip ratio, which the plugin now updates adaptively per frame; check the clipping settings as described in the official notes.