What is implicit modeling?

Implicit modeling describes a shape by a function over all of space instead of by its surface. For every point p the function answers one number, f(p): negative inside the part, positive outside, zero on the surface. When that number is the distance to the surface, the function is a signed-distance field (SDF), and the shape is everything where f(p) ≤ 0. Implicit CAD is CAD built on such fields; FieldCAD is one, and it runs in your browser.

Boundary CAD and implicit CAD

Conventional CAD stores a solid as its boundary: faces trimmed by curves, stitched together within a tolerance. Every operation has to compute where surfaces meet and rebuild that stitching, and that is where it breaks — a boolean that leaves a sliver, a fillet that fails on one edge, a shell that cannot offset a tight corner, a feature that loses its reference when an earlier one changes.

A field stores no boundary, so none of that work exists. The operations are arithmetic on numbers, the same at every point:

• Union is the smaller of two fields, min(f₁, f₂); subtraction is max(f₁, −f₂); intersection is max(f₁, f₂).
• Offset by a thickness t is f − t; a shell of wall t is |f| − t/2.
• Blends are a smooth minimum: a rounded joint between any two parts, whatever they touch.

None of these can fail: there is no intersection to compute and no topology to repair. The cost of a design grows with the number of operations, not with how many faces they touch, so a part filled with thousands of lattice cells is as easy to cut, shell or blend as a cube.

Fields drive the geometry

Because everything is a field, any field can steer any operation. A wall thickness can follow the distance to a hole, a measured stress, or a formula; a lattice cell can grow along the load path; a pattern can follow a surface. This is field-driven design, and it is what makes implicit modeling strong where conventional CAD is weak:

• Lattices and infill — gyroids and other triply periodic minimal surfaces (TPMS), beam lattices, Voronoi structures, graded by any field, for parts printed light and stiff.
• Lightweighting — cut a window into a part and fill it with a lattice blended into the rest (a crank arm).
• Scans and organic shapes — a scanned mesh becomes a field you can offset and shell (a wrist brace on an arm scan).
• Analysis-driven parts — a stress analysis on the part sets the infill's wall thickness (a bicycle stem), and topology optimization finds where material belongs (a cantilever).

How fieldCAD does it

A FieldCAD design is a graph of blocks: shapes, booleans, offsets, lattices, fields, analysis and optimization. Change a number anywhere and everything after it follows. The kernel runs in the browser tab, on your own graphics card, so there is nothing to install and the geometry is computed on your machine. STEP files import with their faces and edges kept, so an implicit operation can start from a real CAD part; meshes for printing export as STL, OBJ or 3MF, and a solid can export as the field itself, a 3MF level set. An AI assistant can read and write the same graph from a description of the part.

Open a demo to see it at work, or start a document — it is free.