If you need a tools that will help you to model / draw 3d reinforcement with Grasshopper then check out T-Rex plugin. It’s open-source (MIT License). Right now it’s beta version, so any feedback would be really helpful.
Introduction video: https://www.youtube.com/watch?v=r2GVTfjJHdA
Manual / instructions: https://code-structures.com/T_Rex_Manual/Manual%20for%20T-Rex.html