Is there such a thing as Stochastic Scratches?

[Ihno]

Looks awesome!
Do you use the color to bump map for the scratches?
And what res has the texture?
I'm doing an old guitar in my sparetime and tried alot of stuff to get the micro scraches right.

[stevejjd]

Thats sick bro -

[kosso_olli]

Do you use the color to bump map for the scratches?
And what res has the texture?

Yes, the map is plugged into a color2bump node. The texture has a resolution of 1024x1024. Sounds small, but it tiles quite well.
You have to experiment though, so the effect is not overdone. Otherwise you will start to see scratches everywhere, not just around the highlights. Thats already the case in the image above the headlight cover.
Also, sampling is getting hard with super bright lightsources. Which I had, because the images are all night-shots. I needed to crank up the render settings quite a lot.

[MANUEL_MOUSIOL]

Problem with these scratches is you can still see them in other angles, not just from camera direction, know what I mean? Usually they appear only around harsh highlights. I couldn't achieve that look just with Bill and a Fresnel falloff

[stevejjd]

Problem with these scratches is you can still see them in other angles, not just from camera direction, know what I mean? Usually they appear only around harsh highlights. I couldn't achieve that look just with Bill and a Fresnel falloff

Is that because it needs to be done with a Normal Map? - I think the bump map may be too simple. It should be done with a normal map because the glints react better to the direction of light sources ---- I think.

- Should the scratches be anisotropic as well?
- Should the scratches affect the Reflection Glossiness by making it more rough?

I would like to hear what Vlado has to say - Or some other really advanced CGI artists.

[stevejjd]

The other thing I notive about micro scratches on car paint is that there are so many colors in the valley of the scratches. I would be good to plug a multi-coloured texture into the reflection map, masked to only be colourful in the valleys of the scratches.

[MANUEL_MOUSIOL]

Maybe that's the car paints flakes being it in the open?
Maybe the thin film shader osl could help...

[kosso_olli]

From my experience, a scratch doesn't show any color. The scratch itself basically lightens the color beneath it.
For the work I do, somehow a simple bump map always did the trick.

[fraggle]

I support the idea to get the micro-scratch implemented. It's impossible to get them only in the bright area.
Could a vrayextratex with scratch texture combine with specular renderelement be a good post prod workarround?
Or even better, combined with a curvaturemap, if and only if it exist (doesn't exit on my setup with vray next)

[fraggle]

can't see it because VrayCurvature is not compatible with VrayGPU

[MANUEL_MOUSIOL]

How would you use curvature for that?

[fraggle]

Push the vray curvature as well as the scratch as extratext renderelement then used the curvature as mask?

[MANUEL_MOUSIOL]

but what does curvature have to do with where the scratches would be visible (i.e. bright highlights)...

[fraggle]

Curvature map output concave/convex surface of the model and highlight happens on convex shape. A Dirt map (AO) could probably do the same, but it will have to be combine to something elese to be as efficient as curvature, so it won't be compatible with render element once combine to another shader.

[super gnu]

Curvature map output concave/convex surface of the model and highlight happens on convex shape. A Dirt map (AO) could probably do the same, but it will have to be combine to something elese to be as efficient as curvature, so it won't be compatible with render element once combine to another shader.

dont highlights happen on convex shapes,and flat surfaces too !?