Detecting edges within a Shader is fairly simple these days. We get the Rounded Edge Operator in VOP’s since some time now. I have not seen many using it for its full potential and usually it just acts as a soft edge option on the Principled Shader.
However we can use the Rounded Edge Operator to add damages to edges of geometry.
The setup is fairly simple:
We take the normal and use rounded edge operator to calculate the edges. we then subtract the original normals from the new calculated normals. This is basically the entire setup needed. After this step we need to make sure we transform the working space from Camera to Object space. This is very important and in Houdini you will need to handle the different spaces yourself. So be aware of that. It can take a while to understand it and i’m not going into detail why you have to do this here.
Once we have all this done we calculate the length of the normal and use a fit operator to give it more contrast. Think of the fit node here like a level operation in photoshop. Its taking an input value from 0-1 (or user defined) and remaps it to a new output. To add more contrast we will change the incoming min and max and bring the sliders more closer together.
In the network above we simply output the float value to our emission (Ce) and get following result with some default platonics and robby:
You can also output the absolute value of the normal which will split it into rgb accoring to XYZ direction:
However for this we can just work with float value as we’re just looking for a mask on the edge.
We can now add some noise to the incoming normal and do anything with it that you want, for example adding some edge wear mask:
At this point we put everything within a subnet so we can make it into an HDA or just save it in the gallery for reuse. The fit operation we again fir the noise between different radius:
From here its now easy to control the thickness, contrast and noise to get desired results
From here on you can experiment with different things. A few examples below:
Note that in general the Rounded Edge Operator works best with Low Poly, non beveled objects. If you have a high res modul you can replace the Rounded Edge Operator with the Curvature Operator to achieve better results.
Another note in Blender the Bevel Operator in Shaders is the same as Rounded Edge Operator in Houdini’s Shaders