@Sabine Freyer It depends on the shading model you go for. The most established for realism is to not use a specular map but just the roughness instead. The amount of specularity is then just dependant on the IOR of the material. It can still be useful to modify this regardless for art direction.

But that means there is no accurate way to get a specular map out of a roughness map since they are different things. I would try incerting is and adjusting the levels until it looks right under different lighting conditions.

*@Michael Schwarz* Assuming your nodes exactly match what's in the video...you need to be in Cycles render preview mode. Material Properties>Settings>Surface>Displacement should be set to Displacement and Bump OR Displacement Only. And your plane needs a good amount of geometry by way of manual subdividing and/or a Subdivision Surface modifier. I'd also suggest not messing with with the plane's scale just to eliminate a variable. This stuff was covered in some previous lessons...might want to go back and rewatch some things.

*@Blair Martin* Thanks a lot. Render engine cycles and the render preview mode did the trick. For a beginner it is a bit difficult to understand the differences between the render engines. With evee you have just a plane with cycles you have a curved plane. That means if you like to set up a scene you'll have to decide in advance with which render engine you are going to manage the output. The workflow to create the scene would be different depending an the render engine you are working with.

*@Michael Schwarz* Yes, correct. The only way to do displacement in Eevee currently is to use the displace modifier on the mesh. But for this you cannot use the shader nodes, you have to use a texture, like a baked image. I will go over baking in the final chapter.

*@Blair Martin* Yes, that's correct, thanks for clarifying!