Hi Gabriel,
You can use procedural symbols in ArcGIS Pro for creating 3D-symbols/realistic-buildings for your polygon features. Procedural symbols are created from a Esri CityEngine rule package file (.rpk).
The rules have to be authored in CityEngine and then can be exported out as rule packages for consumption in Pro. So if you want to create a very specific type of symbol then you will need to author that rule in CityEngine.
However, there are already a number of rule packages that are available to use. You can search for these here and maybe one of these will satisfy your requirements - http://www.arcgis.com/home/search.html?q=rule%20package&t=content&start=1
Additionally, you can also look at the Procedural Symbols style in ArcGIS Pro - there are a couple of symbols available there. Just add the style to your Pro project and pick a procedural symbol from the Gallery. Please take a look at Pro help for more information: Procedural symbol layers—ArcGIS Pro | ArcGIS for Desktop
Procedural symbols are highly configurable. All the symbol properties (also known as attributes) exposed by the rule can be configured in Pro. You can map the symbol properties to your feature class attributes. So for example, if a rule extrudes building footprints then you can map the 'extrusion height' symbol property to your feature class field that has height information. Now all features will be extruded to different heights based on their height field values.
You should also look into the following GP tools:
Features From CityEngine Rules—Help | ArcGIS for Desktop
Layer 3D To Feature Class—Help | ArcGIS for Desktop
Thanks,
Deepinder Deol