Rendering Micro Scratches for Glossy Surfaces

[kweechy]

Been doing some R&D on how to really achieve this effect in a believable way. Last night I painted a 4K map with a Wacom and 1px brush in Photoshop. I tried every way possible of applying it, played with varying bump values, even tried to tile it 9 times to make sure the detail was uber fine...nothing really got close to that look though.

Has anyone here experimented with this and found a decent cheat for getting those radial scratch patterns to form under heavy spec/reflection points on the surface?

Attached a real life example of this effect, look at the bottom of the image at the reflection and how all the micro scratches end up appearing to be radiating around the highlight due to how they catch the spec.

[instinct]

I assume the problem is not in generating detailed enough source maps, but that the detail is lost in filtering. You'd have to render with REALLY crazy quality settings to preserve that kind of detail without flickering/noise i'd say. I remember reading in a making of for some "plane movie" that they had a proprietary fake shader for microscratches on the cockpit glass. I wonder if something similar to the VRayFlakeMtl would be able to do the trick, as it seems to serve a similar purpose (preserving microdetail without making rendertimes explode)

Regards,
Thorsten

[Dariusz Makowski (Dadal)]

I think in order to do it u would need to set up ur texture blur from 1.0 to 0.0000001.

Also use a very high AA filter to actually render them. Can u share texture u made ? I'd like to have a play with it see what we can get.

[kweechy]

Sure I'll post the texture when I get home tonight.

I was using 0 texture blur and even tried rendering with DMC settings of min = 24, max = 100, threshold = 0.002 but it was still just looking sloppy and loose. This was with a 4096 texture, painted with a 1px pressure mapped hard brush, and I even tried repeating U and V upwards of 9 times to attempt to crank the detail.

Someone I work with is trying as well, but with the scratches mapped to the reflection glossiness. The only problem I can see with that is it will illuminate all scratches indiscriminately and not necessarily give you that radial pattern. In the real life effect, any scratches than radiate out from the specular highlight will not really illuminate, while the ones that radiate WITH the highlight end up glimmering slightly...so it always appears you've got scratches flowing circularly around specs, but the real reason is they only catch that spec when they're perpendicular to it.

[kweechy]

Got this figured out with really nice results. I'll post later on, right now I'm using studio assets and can't attach images.

[Dariusz Makowski (Dadal)]

Cant wait to see it

[kweechy]

Heading out the door and don't have time to go into the details, but I'll make a post when I get a sec to explain the setup.

[waaazoo]

wonderful ! this is looking perfect.

[super gnu]

very nice effect youve achieved thre.. veeery interested to see how you managed it, and if it was without intergalactic render settings

[kweechy]

Updated image after playing around more last night...added paint flakes for the hell of it too. I'll get a chance to walk you guys through the setup today.

Render times aren't horrible. 10m for half HD with FULL production settings 8-24 DMC samples, 0.04 threshold, etc.



Basically the solution in the end was to use a bump map setup, but it got pretty tweaky and finicky. It's quite literally just a very fine scratch map that I've painted, made @ 4K resolution, tiled 5 times for mega detail. This is applied to a 100% reflective material to use as a cleacoat in a VRay BlendMtl with a Fresnel map to control the contribution.

For the master clearcoat Mtl, I'm using 3 layers of this effect. One with a high bump value, medium and low, all in a VRay BlendMtl @ varying opacities. On top of them all is a standard, non-bumped 100% reflective material, and its blend amount is controlled with an HSV remap on the scratch map I painted (so that the pure reflection doesn't replace the scratched parts too much).

I think what I might do is create a 3D Ocean account and put up all of this work (textures, lighting file, shaders, etc) for people to grab a copy if they want. I know free stuff is better, but this way I can support my hobby/development work on the side a little as well...not sure how people feel about that yet.

[Dariusz Makowski (Dadal)]

Looking great! But shouldnt flakes be a lot more dense?

[kweechy]

Absolutely, I just got fed up of waiting for the flake tex to bake on every test render

I think my density is at 5 or so right now, should probably go to maybe 15.

[jasonhuang1115]

Hi kweechy,

Please give us a heads-up whenever you have the stuff up at 3D Ocean. I for one am interested in checking it out.

Thanks.

[kweechy]

Sure thing, I'm just compiling a solid controller setup for ease of use on this thing. That way you just apply the final clearcoat to a BlendMtl and have all the controls lying inside the clearcoat, rather than scattered all over the various nodes in the Hypershade.

[DPGrafik]

any news on the shader upload?