Image to STL workflow: choose the job before the converter

A relief starts from a height field. The front surface varies with brightness or estimated distance, and the back is flat. It is the right workflow for portraits, plaques, lithophanes, carved panels, and decorative tiles. It needs one view and a clear subject, and it accepts the fact that hidden geometry is not recoverable.

A silhouette extrusion starts from a mask. The shape is extruded to a constant thickness. It is the right workflow for logos, signs, badges, and simple flat parts. It needs a clean vector or a high-contrast raster, not a depth model. A full reconstruction starts from multiple views or a scan and tries to recover the whole object. It needs more input and a different toolchain.

A height image is a surface sample. A slicer needs a closed volume. If you import a grayscale image directly, most slicers either refuse it or create a zero-thickness sheet. A useful relief mesh needs a top surface, side walls, and a bottom face, and the walls must meet both surfaces without gaps.

The free preview STL is a low-resolution closed mesh for scale and orientation checks. The production bundle builds a denser watertight mesh from the raw depth field and validates the closed topology before export. Neither is G-code, and neither chooses print orientation, supports, or toolpaths for you.

Automatic repair is not a substitute for construction. A repair tool can close a hole, but it can also remove a thin feature or flip a normal. If the mesh needs repair, inspect the repaired result against the preview and keep the original file. A repaired mesh that no longer matches the approved preview is a different part, even if the filename is the same.

For a relief, use a sharp photograph with one clear subject and a quiet border. Front-facing portraits, pets, products, and architectural details are easier than groups, glass, smoke, and fine hair. Crop before depth estimation so the subject occupies the useful range.

For a silhouette, use a high-contrast image or a vector. Anti-aliased edges, JPEG halos, and thin lines become manufacturing problems. Check the smallest feature against the nozzle or cutter before converting. For a full reconstruction, use several views with overlapping coverage and consistent lighting; one photo is not enough.

A model that looks good in a viewer can be the wrong size in the slicer. Set the finished width, relief height, base thickness, and mesh grid deliberately. A 120 mm plaque and a 300 mm wall panel need different relief heights and base thicknesses even when they use the same image.

The mesh grid controls how much detail the geometry can carry. Too little and faces become facets; too much and the file grows without adding information. Compare the grid with the nozzle or cutter and inspect the preview before choosing a dense production mesh.

STL has no unit metadata. The slicer or CAM package decides whether a number means millimeters or inches. Write the intended unit in the filename or the job record, and confirm the bounding box after import. A model that is correct in one program can be ten times too large in another. If the target program has a unit setting, confirm it explicitly before scaling the mesh.

The free path includes source checks, shaping, a 3D preview, an 8-bit PNG, a compatibility 16-bit container, and a preview STL. It proves that the scene interpretation and the dimensions are worth continuing. It does not prove production precision, because the compatibility file derives from the 8-bit preview.

One approved production job re-encodes from raw float depth and returns the source EXR, verified true 16-bit forward and inverse PNGs, a preview, a watertight STL, and a manifest. A confirmed provider failure refunds the credit. A completed estimate you decide not to use is not a technical failure.

Confirm the workflow, the direction, the subject order, the background, the finished size, the relief height, the base, the mesh grid, and the target process. Open the STL in the slicer or CAM package at real size. Check the bounding box, the closed topology, and the smallest feature.

If the preview already shows a flat subject, a broken border, or an impossible slope, do not buy a denser mesh. Fix the source or the range first. The cheapest failure is the preview you reject.