3D Modeling Programs

 3D modeling software is mostly used for making props and characters, but can also be used for generating textures.

• For Source Modeling, the model editor application must be able to export models in Valve's SMD format.

With Half-Life: Source model exporter

• kHED - a free and simple modeling program.
• 3DS Max - a high end suite for animation, modeling and rendering. one of the industry's best. Has a large support network and many plugins. Valve used 3DS MAX for the original Half-Life (hence the name of studiomdl.exe and .smd) there for exporters exists for all versions from 3 to 9, importers for .smd also exists for most versions as well as a .vta exporter and .vtf importer.
• Blender - a high end, free, open-source, suite for animation, modeling and rendering.
• Cinema 4D - a popular modeling program, especially in TV media. It is a powerful toolbox. It's exporter currently only support static prop exporting.
• fragMOTION - a low end modeling and animation suite, but it has tight integration with the structure of half-life models and supports weighted vertexes. FragMOTION comes with .smd importer and importer as well as .vtf importer.
• GMax - a discontinued free version of 3ds Max currently distributed by Turbo Squid. Both, an .smd exporter and importer exist for GMax.
• Maya - a high end suite for animation, modeling and rendering. An advanced .smd and .vta exporter exists as well as a limited .smd importer.
• MilkShape 3D - a low end, popular and simple to use 3D modeling program. Comes with .smd exporter and importer.
• LightWave 3D - an excellent mid range modeling and animation suite. Currently, a LightWave-only exporter supports static props.
• Autodesk Softimage - (formerly Softimage XSI) an excellent mid to high end modeling, animation and rendering suite. Valve used Softimage for most models in Half-life:Source, the Softimage Mod Tool exporter can be used with a little modification.
• Softimage Mod Tool - (formerly XSI Mod Tool) a free version of Softimage with limited capabilities compared to the full version of Softimage. Valve developed the exporter for the Softimage Mod Tool together with the Softimage developers, and as a result the exporter has full support for importing and exporting .smd and exporting of .vta.

Without Half-Life: Source model exporter

• Wings 3D - a free, open source Nendo-like natural modeling  IDE.
• Clara.io - online 3D editor - a free 3D modeling and animation package similar to 3DS Max and Maya but it runs in the web browser using WebGL.