STEP native preview Mesh cache warm

Saptasati presents

Free AndroidSTEP/STP viewerfor offline CAD review.

PartLens is built from scratch by Saptasati. Open STEP and STP files without upload, login, or ads. Inspect assemblies, cut sections, measure features, and join Google Play testing before wider release.

Join Google Play testing See the processing unit

Next Owned processing unit

01 / Built inside Saptasati

We are not wrapping a viewer. We are building the processing unit.

PartLens is designed around a controlled pipeline: STEP/STP intake, native model packaging, mesh caching, feature indexing, datum state, screenshot evidence, and exportable manufacturing context. Owning that layer lets us make the app faster, more practical, and less dependent on someone else's black box.

PARTLENS_UNIT v0.beta

01STEP ingestRead native files, preserve assemblies, prepare for Android.
02Native cacheReopen heavy files quickly without reprocessing every time.
03Feature indexFind holes, slots, faces, edges, and usable pick targets.
04Action layerDraft, compare, export, and convert from the same model brain.

Next Quick rendering, native files

.STEP

.STP

Native cache

Preview mesh

GPU draw

02 / Quick rendering, native files

Open STEP and STP files offline on Android.

PartLens is a free STEP viewer and free STP viewer for Android devices. Files load directly: no intermediate upload, no third-party viewer in the loop. The processing unit reads Part-21 B-rep, tessellates it on-device, and an instanced renderer turns repeated parts into one shared mesh and a GPU draw call, so assemblies with hundreds of occurrences still stay smooth.

No upload-first workflowBuilt for shop-floor trust. Android CAD viewerInspect parts where the work is happening. Instanced GPU drawsOne mesh, placed thousands of times.

Next Free STEP convertor

.STEP / .STP

PartLens ConverterLocal

.partlens

03 / Free STEP convertor

Preflight on a PC. Open instantly on the phone.

PartLens Converter is a free Windows tool that runs entirely on your own machine — no upload, no account, no server in between. Point it at a STEP/STP file and it packages a .partlens file: pre-cached and measure-ready. Heavy assemblies that would take a minute to re-tessellate every time open in a blink, because the expensive work only happens once.

Runs 100% localNo upload, no account, no internet. Outputs .partlensPre-cached and measure-ready for Android. Free, no limitsConvert as many STEP files as you need.

Next Datum drafting

04 / Drafting without ceremony

Measure STEP files on Android with usable datum context.

PartLens supports practical STEP file measurement on Android: choose a zero point, define direction, snap to centers or vertices, and produce a clear coordinate story for inspection, discussion, or first-pass manufacturing review.

Next Compare & LH/RH

05 / Iteration intelligence

Compare revisions, catch LH/RH intent, and stop guessing.

The compare layer is where PartLens gets loud. We are baking in iteration comparison, changed-feature surfacing, mirrored LH/RH awareness, and the kind of practical manufacturing deltas that help teams understand what actually changed between two files.

Rev A Mount bracket Baseline STEP

Delta 4 hole shifts 2 dia changes, 1 boss moved

Rev B Mirror candidate LH/RH intent detected

Moved face Hole pattern Slot update LH/RH check

Next Everything else, baked in

06 / Everything else, baked in

Built on-device. Your CAD files stay with you.

PartLens is not a wrapper around someone else's kernel. The STEP engine, the renderer, and the measurement system are written from scratch, in pure Kotlin, so offline STEP viewing, section view inspection, and measurement can work without a network connection.

No INTERNET permissionYour files and your IP never leave the device.

879 KB signed releaseThe whole engine, R8-minified.

Instanced GLES3 rendererOne mesh tessellated once, placed thousands of times.

NURBS & B-rep surfacesPlanar, cylindrical, conical, spherical, toroidal, B-spline.

5,000-part assembly60,000 triangles tessellated in ~120 ms.

STEP section view AndroidIndependent X/Y/Z clip planes, evaluated per-fragment on the GPU.

Magnetic snap measurementVertex, center, edge, and midpoint, colour-coded.

Device-adaptive qualityTessellation density scales to the phone's memory budget.

True STEP coloursRead from the file's presentation styles, not guessed.

Next Google Play testing access

07 / Google Play testing access

Join PartLens Google Play testing.

PartLens is preparing wider availability as a free Android CAD viewer. Join Google Play testing if you want early access, can test real STEP/STP workflows, and want to help shape offline CAD review before public launch.