I'm considering attempting a game built using Panda3D where no objects are built using a 3D editor. It would all be made and rendered using geometric functions. This includes multiple characters running around, spells being cast and buildings and other objects being around.
How viable of an idea is this? Would rendering all of that in real-time be too inefficient?
I have a very vague idea myself of what the game will consist of at this point or else I'd give more details, but I'm really just wondering if the general idea is possible.
Have a look at other games made with Panda3D. see the tutorials, demos, etc. That will give you a good overview of what can be possibly made. Check for the keyword technologies that you need - SSAO, Skeletal-Animation, Physics, etc.
In general, you might want to detalise your idea and see how other games implement parts of it. If there are some unique things that nowhere to be found - then ask about how to make them. Otherwise they are certainly viable (as someone already made them)
Without much more info in the original question, the answer can be only this detailed.
Real-time Geometry Rendering with Panda3D -- Efficient?