@truedxf/render

Draws DXF exactly like an AutoCAD plot. Fast, renderer-agnostic display lists, pixel-tested against thousands of AutoCAD plots.

It walks a model-space or paper-space layout of a DxfDocument and emits a display list that any renderer can draw, such as @truedxf/three.

Install

pnpm add @truedxf/render

ESM only. No DOM and no Node.js APIs: runs in browsers, workers and Node.

What it does

• renderPlot(doc, request, env) returns PlotResult { displayList, view, unsupported, notes? }. PlotRequest picks the layout, the plot area (window with Fit + Center, extents, layout at 1 px per paper unit or an explicit scale) and the canvas in device pixels.
• All geometry work happens here: tessellation, linetypes (including complex linetypes with shapes and text), lineweight widening, hatch fills, clipping. The DisplayList holds batches of Triangles, Lines (1 px), Points and textured Image triangles in strict draw order, float32 positions relative to a float64 origin, clip regions and pick ranges back to entity handles. transferables(list) lists its buffers for postMessage.
• raster: "autocad" (default) computes pixel spans on the CPU with AutoCAD's raster rules for thin lines, arcs, lineweight polygons and fills (PixelGrid, linePixels, arcVertices, fillPolygon) at the driver's 100 dpi. raster: "smooth" gives plain geometry for viewers.
• Properties (PropertyResolver): ByLayer/ByBlock, layer on/off/frozen/no-plot/Defpoints, per-viewport freeze, the plotted ACI palette (PLOT_ACI_RGB), plotted transparency (PLOTTRANSPARENCYOVERRIDE), draw order (SORTENTSTABLE with $SORTENTS).
• Plot styles (@truedxf/plot): CTB pens by resolved ACI, STB styles by name; pen colour, grayscale, screening, lineweight, end / join styles, pen linetypes (fixed and adaptive) and raster fill styles. PlotRequest.styleTable names the table; its bytes come from plotStyleTable, env.loadPlotStyleTable, or the built-in equivalents of the stock tables.
• Stored page setups: PlotRequest.pageSetup plots a layout's PLOTSETTINGS like a non-detailed -PLOT (area, scale, rotation, margins, offsets, style table, switches); PlotResult.canvas is then the printable area.
• Entities: LINE, CIRCLE, ARC, ELLIPSE, SPLINE, LWPOLYLINE, POLYLINE, POINT (PDMODE), SOLID, TRACE, 3DFACE, RAY, XLINE, INSERT/MINSERT with ATTRIBs and XCLIP, TEXT, MTEXT, ATTDEF, SHAPE, HATCH, MPOLYGON, DIMENSION (regenerated with generateDimension when the *D block is missing), LEADER, MULTILEADER, TOLERANCE, MLINE, MESH, HELIX, ACAD_TABLE (its block), IMAGE and WIPEOUT (PNG, JPEG, TIFF, BMP), REGION/3DSOLID/BODY/surfaces as ACIS wireframe (SAT and SAB), proxy graphics, VIEWPORT, PDF underlays (content through env.pdf, e.g. @truedxf/pdf with PDF.js), DWF / DGN underlays (frames only) and OLE frames.
• Fonts and images come from the host through env.loadFont / env.loadImage. Text is laid out by @truedxf/text. env.text.missingFont chooses AutoCAD's missing-font behaviour or a fallback font. Missing fonts show up in PlotResult.notes (font-missing, bigfont-missing).

Importing the package registers every drawer (side effects in src/draw/*.ts). registerDrawer and registerPreparer add more.

Usage

import { readFile } from "node:fs/promises";
import { loadDxf } from "@truedxf/model";
import { type PlotRequest, renderPlot } from "@truedxf/render";

const doc = loadDxf(new Uint8Array(await readFile("drawing.dxf")));
const request: PlotRequest = { layout: "Model", area: { type: "extents" }, canvas: [1600, 1200] };
const { displayList, view, unsupported, notes } = await renderPlot(doc, request, {
  // font bytes by lower-cased file name ("txt.shx", "arial.ttf"); undefined = missing
  loadFont: (name) => readFile(`fonts/${name}`).then((b) => new Uint8Array(b), () => undefined),
});
// view: the world window that maps onto the canvas; draw the batches in order without depth testing
console.log(displayList.batches.length, view, unsupported, notes);

For a paper-space layout pass its name and area: { type: "layout" } (or a window in paper units). Viewers pass raster: "smooth", visibility: "display" and layerVisibility, as viewer/src/protocol.ts does.

Limitations

• Plot styles: pen linetypes on wide polylines and the exact outline of wide pen-linetype dots are approximations; fill styles follow the raster driver only (no PDF tiling).
• Page setups: display and view plot areas are plotted as extents; PLOTROTMODE 0/1 (not in the DXF) is not modelled. Without pageSetup the caller supplies the plot area and canvas (PlotRequest, docs/fixtures.md). Extents plots miss AutoCAD's padding (extents suite 9/18 at F1(r=1) ≥ 0.99).
• Model space is drawn in plan view (the *ACTIVE VPORT view direction is not applied). Perspective viewports are not supported.
• Open features: wide polylines with linetypes, some MULTILEADER variants, XCLIP of ATTRIBs. Raster gaps: exact-pixel ties, spline tessellation, hatch islands, clipped huge arcs (docs/TODO.md).

License

MIT. AutoCAD and DXF are trademarks of Autodesk, Inc. truedxf is not affiliated with or endorsed by Autodesk.