123D Design is a free software from Autodesk that is easy to use and is a powerful tool for creating and the imagination. You can use it on a Mac, PC, iPhone, and iPad.
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PC Requirements:
- Windows 7 (32-bit or 64-bit)
- Intel® Pentium® 4 or AMD Athlon® 64 or later with 2 GHz or faster processor; or compatible
- 2+ GB RAM (1.5 GB minimum)
- 1.5+ GB free disk space (for installation)
- Direct3D® 9 or 10 graphics support with 64+ MB
Mac Requirements:
- Apple® Mac OS® X, version 10.7 or later with 64-bit Intel processor
- Apple® Mac® Pro 4.1 or later; MacBook® Pro 5.1 or later (MacBook Pro 6.1 or later recommended); iMac® 8.1 or later (iMac 11.1 or later recommended)
- 3 GB of RAM (4 GB recommended)
- 2.5 GB free disk space for download and installation (3 GB recommended)
- 1280×800 display with true color (1600×1200 with true color recommended)
- All Mac OS X supported operating system languages
tutorials:
Creating Objects
Moving, Snapping, and Cruising
Grouping Objects
Edges, Faces, and Points
123D Design for iPad
Add, Subtract, and Intersect Objects