Are there any good open source .NET chart components out there that are good for large data plotting and real-time charting? I saw some related topics but they were since 2010 and older, so I'm not sure if they are still valid.
Syncfusion provides a Chart library for all .NET platforms. While not open source, the libraries are available under a community license as well (see details below).
The whole product is available for free through the community license if you qualify (less than 1 million USD in revenue).
Note: I work for Syncfusion.
So, even though this is quite an old question, it has popped up on recent google searches so I am posting this here so that it may help anyone still searching for something similar!
A good option is LightningChart Ultimate! LightningChart provides an entire suite of hardware-accelerated charting components that can be especially useful if real-time performance matters to your application. With the support of real-time rendering of upwards of 15+ Billion data points, 2D and 3D chart support, along with a comprehensive API for theming and customization and a very shallow learning curve, LightningChart can help your project deal with any data visualization challenge that crops up! We also have various licensing options for students and teams of any size.
I work as a senior dev for LightningChart, so if you have some queries, please don't hesitate to ping me.