I found on the net a great lesson on creating realistic micro-scratches with Vray (and 3ds Max) . And I decided to post the translation. I fixed some wrong places in the original article, and also added.
The principles of creating such a shader are universal, which means you can apply them not only in V-Ray + 3d Max, but also in any other 3D package (Maya, Houdini …)
The radial “spider web” around the reflection flare is caused by micro-scratches reflecting light from different angles. We often see this effect on worn, scratched, worn surfaces.
For quite some time I tried to achieve this effect in VRay, but … to no avail.I looked for solutions in the forums, and also experimented and I think I found a method that gives good results. Naturally – made a lesson.
First of all, forget about using the normal bump texture; I’ll say from experience that it will not produce the desired effect. To simulate these extremely tiny scratches, you need to use the Normal Bump (Normal Map).
It’s better to draw it in Photoshop, as there you can easily make it tileable (seamless).
Draw a bunch of scratches in the center of the image, make sure that none of them touch the borders of the image. Then use the Offset filter (Filter -> Other -> Offset). Using it, move your texture exactly half in both axes and draw a few more scratches in the white areas. Continue until you “scratch” everything. [ there is a video in the original article where the author shows how he does it]
Here is the map I received (if you click, it can be downloaded in high resolution):
Now using NVidia Normal Map filter (a free plugin for Photoshop), we will generate a normal map.
Important! Do not use the normal map above. It is provided here as an example only. You need to create a map in 4k resolution yourself.
Great, now that we have a normal map, we can create a VRay shader.
The material will be created perfectly reflective. We take VrayMtl, the color in the Diffuse slot is pure black, in the Reflection slot it is pure white, we DO NOT put a tick next to Fresnel reflections .
In the Bump slot, we throw the standard Max Normal Bump and load our resulting normal map there. Make sure that Gamma for the loaded normal map is set to 1.0 and Filtering is disabled (on the Bitmap Parameters scroll). In the field opposite the Normal slot, I will set the normal force to 1.5.
Now convert the material to VrayBlend (leave the existing material as a submaterial) and duplicate the first layer several times.
For each subsequent coat layer (Coat Material), make the force of the normals a little less. This will create a smoother transition around glare on micro scuffs.
For example, I used 1.5 for the base material, 1.0 for the first layer, 0.5 for the second, and finally 0 for the third. The last layer will give a clean reflection without scratches. By changing the Blend amount for this (third) layer, you control the strength of the scratches. To make the surface less worn out, you can wind up the mixing force (make the mixing color whiter) for the third layer:
As a result, we get this
In principle, that’s all!
If you need such scratches on polished plastic – no problem. Create a new VrayMtl, customize the color of Diffuse, etc. and use this material as the Base material in the new VrayBlend.
Now add our scratched reflection shader to the Coat slot. And in the Blend slot we assign the Falloff card and set the Falloff Type – Fresnel, in the parameters we specify the IoR value that we need (usually from 1.4 to 3).
TA-dah! Your shabby plastic!
In the same way, you can make scratches on any material. True, you should pay attention to the base material – if it has strong glossy reflections, then it is better to turn them off, and use reflections from the coating material.
Naturally, behind the scenes there were such moments as a careful selection of the strength of normal maps on different layers or a change in the very number of layers … But this will be more than enough for a start.
I have a series of chic articles about what makes a 3D picture realistic .
Perhaps you know a different method to achieve a similar result. If so, please share it in the comments.