Invisible Faces

Okay so I have made some models for a golf game I am designing but I can’t seem to import them into UE4 without some faces being invisible. I use blender and I know when I look online for a solution it comes up with being one-sided polygon error but I can’t see online on how to actually fix this.

Two sided materials can be a fix, but first you should check the models in blender to make sure there aren’t any reversed normals. If needed, below are the steps to view normals in Blender:

Select your model in blender.

In the properties shelf, find the Mesh Display panel. There you will find the settings for viewing Normals. click on the highlighted face icon in the Normals options.

Now you should see green spikes coming up off each face in your model. If you can see the spike in Blender, you’ll be able to see the face in UE4. If you have any faces where the green spike is facing the wrong direction, such as facing into the model, those faces also won’t be visible unless you’re inside the model.

Select any faces with incorrect normals and use “Flip normals” to fix them. Export the model and bring it back into Unreal and it should be fixed.

NOTE: If you want to be able to see both sides of a face, as in the case of a curtain made of a single plane, hair made out of planes, etc, then you’ll have to use two sided materials as Redbox advised.

Use TwoSided materials.

Stop giving this as an answer, its not a proper solution and has a negative performance impact.
Always suggest to double check if there are flipped normals.