Since the company was formed more than 25 years ago, Pixar has used an in-house product called Renderman to help add digital effects to its films. Those blockbuster include Toy Story, A Bug's Life, and many more. Pixar also sold (and continues to sell) Renderman to anyone who wants to use it, and recently cut the price from $1300 to $495. A good reduction, but still not quite right for my loyal audience. However, as of now, the news gets even better. For non-commercial use, Renderman is totally free. Just download and install it from the link below.
Before you rush to download it, however, it's worth noting the following. You'll need a 64-bit version of Windows, and as powerful a PC as you can find, it order to get the best from it. You'll also need to dedicate some serious time to learning it, as this is not a package you can master in a weekend. Also, be aware that the free version is strictly for non-commercial use only, so you can't use it within your company. Finally, you'll need to register on Pixar's forum before you can download the installer, and their forum software is pretty much the worst I've ever encountered. But it's definitely worth persevering.
The download is only 10 MB, and is malware-free according to VirusTotal and Web of Trust. However, the installer will subsequently download between 500 and 1000 MB of additional files when you run it, so take care if your broadband connection has a monthly allowance of less than that.