3D modeling: definition, methods and free software

Everything you see in an animated film, a video game, a virtual tour or an architect's model was first modeled. 3D modeling is the first stage of the pipeline: before textures, lighting, animation and rendering, you need a shape. This guide explains what a 3D model is, the main methods for creating one, the free software to get started with, and how to progress.

What is 3D modeling?

Modeling in 3D means describing an object by its geometry in a three-dimensional space. The most common form is the polygon mesh: vertices (points in space), connected by edges, which bound faces. A cube has 8 vertices, 12 edges and 6 faces; a game character has thousands of them, a film character hundreds of thousands.

Other representations exist: the mathematical surfaces (NURBS curves and surfaces) of industrial design software, the solids of CAD software, the point clouds produced by a scanner. But for images, animation and video games, the mesh remains the basis, and it is the mesh that gets textured, animated and rendered.

The main modeling methods

Polygonal modeling

You start from a simple shape, a cube or a cylinder, and transform it: extruding a face, adding edge loops, bevelling, moving vertices. It is the most widespread method for objects, sets and game characters. Quality depends on topology: four-sided faces (quads), well distributed, which deform cleanly when animated. The low poly style is a deliberately pared-down version of it.

Digital sculpting

You work a very dense mesh like clay, with brushes: you dig, inflate and smooth. It is the method for organic characters and creatures. The sculpted model is then often redrawn as a lightweight version, a process called retopology (in French), and its details are transferred into a normal map (in French).

Parametric modeling (CAD)

You build the object from dimensions and constraints: a dimensioned sketch, a 20 mm extrusion, a 5 mm hole. Each step remains editable in the history. It is the method used in engineering, in mechanics and in the 3D printing of functional objects, where precision matters more than appearance.

Procedural modeling

You describe rules rather than shapes: a staircase whose number of steps is a setting, a forest whose trees spread themselves out. In Blender, this is the role of Geometry Nodes, covered in detail in the tutorial on procedural modeling with Geometry Nodes (in French).

Capture: photogrammetry and scanning

You reconstruct a real object from photos taken from every angle, or with a 3D scanner. The result is realistic but heavy and irregular; it is cleaned up afterwards. The photogrammetry in Blender tutorial (in French) shows this step.

Free 3D modeling software

Blender is free software, distributed under the GNU GPL licence: it is free for any use, including commercial use, and covers the whole pipeline, from modeling to rendering. It is the most complete choice for images and animation, and the one whose community publishes the most tutorials.

FreeCAD is an open-source parametric 3D modeler, designed primarily to design real-life objects of any size, with no licence fees. It suits mechanical parts, enclosures and printed objects that have to fit together.

SketchUp Free runs in the browser, with no installation. It is popular for sketching a building or an interior layout, gives access to the 3D Warehouse model library and exports to STL, among other formats. Its terms of use should be read on the publisher's website before a professional project.

Free online 3D modeling and 3D drawing

For a first try without installing any software, an online 3D modeling site such as SketchUp Free is enough to assemble simple volumes, make a first 3D drawing for free and export it. Browser-based tools are, however, more limited than installed software, and they depend on your connection. As soon as you need to sculpt, unwrap UVs or render a realistic image, it is better to move on to Blender.

Getting started with 3D modeling in Blender

1. Learn to navigate in the 3D Viewport and remember a few keys: the Blender shortcuts guide sorts them by editor.
2. Model simple objects in Edit Mode: a mug, a chair, a lamp. Extrude (E), edge loop (Ctrl+R), bevel (Ctrl+B) and the Subdivision Surface modifier are enough for many objects.
3. Apply materials and textures, with the Blender textures guide.
4. Light and render a first image, with an HDRI.
5. Choose a speciality: characters, sets, architecture, technical objects.

The guide to learning Blender takes you through this path in seven steps with the free official resources, and the article Blender 3D, free 3D software (in French) introduces the software and its installation.

3D modeling for architecture and printing

In architecture, the model is often drawn in specialist software or in SketchUp, then imported into Blender for materials, lighting and photorealistic rendering. Keep real-world units (metres) from one application to the other to avoid scale problems.

For 3D printing, the model must be closed, with no faces passing through each other, and with sufficient wall thickness. The guide on 3D printing with Blender covers preparation and STL export in detail.

Training in 3D modeling

Courses at a school or online range from a few days to several years, depending on the target job: video game modeler, character artist, architectural 3D artist. Before committing, try it for free: Blender's official resources and one personal project a week are enough to find out whether you enjoy modeling, and they already make the start of a portfolio. To find assets to study or to use in your scenes, the guide to free 3D models for Blender lists sources and their licences.