Circular ‘spiderweb’ around bright highlights in the reflections, caused by microscratches catching light at different angles. We see this effect quite often on real world surfaces that have been scuffed, scratched and worn out for a while.
Over the years, I’ve tried to achieve this effect in VRay for quite a few times… unsuccessfully
After finding some leads on how to approach this on VRay forums, finally I think I’ve got a method that gives good looking results, naturally I also made a tutorial :)
First of all, forget about using a regular Bump map, it simply doesn’t look right in my experience. You need to use a Normal map to simulate those extremely tiny scratches.
This sort of map is best hand drawn in Photoshop, since you can easily make it tileable. Draw a bunch of scratches in the center of the image, making sure none of them approach the borders. Then, use Offset filter and draw a few more in the white areas. Keep doing until everything is well covered up in scratches.
Here’s a quick video on how I do it and my resulting map.
Now using the NVidia Normal Map filter, generate a Normal map.
Ok, now that we got the map, we can create our shader.
The shader we are creating is going to be pure reflection. So start with a Vray mat with pure black Diffuse, pure White Reflection and no Fresnel.
Add Normal Bump to the Bump slot and load in the map. Make sure it’s Gamma is set to 1.0 and filtering is disabled. I’ll use the strength of the Normals at 1.5
Now convert the material to VrayBlend and duplicate this first layer a few times.
For each subsequent coat layer, lower the Normal strength a bit. This will create a more gradual falloff around the highlights.
So in my example I used 1.5 for the first layer, 1.0 for the second, 0.5 for the third, and finally 0 for the fourth. This last layer gives pure, smooth reflections, without the scratches. You can adjust the blend amount of the last layer to control the strength of the scratches. Just make the pure reflection stronger to make it less worn.
So far the result looks like this:
This is basically our completed Reflection coat.
If you want to add these scratches to a material like polished plastic – it’s easy.
Create a new material, set up your diffuse color/etc and use it as the base layer in a new VrayBlend.
Now add our scratched reflection shader to the Coat slot and use a Falloff map in the blend amount slot, set it to Fresnel (1.4~3)
Ta-da! Your plastic now has a scratched up clear coat.
Same technique can be used to add these scratches to any other material. Just look out for the ones that already have strong glossy reflections – it’s best to disable them altogether and just use the coat.
Obviously there are still some things to tweak, like adjusting the normal strength in different layers or increasing the number of layers and so on, but I think this is a pretty good starting point!
Perhaps you use a different method to achieve this result? If you do, please share in the comments!