Using KeyShot 8's Geometry Flakes for Stochastic Flakes. Possible?

[monson67]

For a more detailed explanation as to what stochastic flakes are: https://www.fxguide.com/quicktakes/v-rays-practical-stochastic-rendering-of-spec-y-things/

Essentially, Stochastic Flakes are physical flakes with random rotation, distributed over/into a surface. The random rotation is what makes individual flakes glisten depending on the angle of view. As a couple examples, think about freshly fallen snow or metallic paint.





This sparkly effect is dependant on the flakes having that random rotation. It's what makes some flakes reflect light at only certain angles.

I was really hopeful that the addition of flake geometry in KeyShot 8 would allow me to add this. However, as the flakes are generated/populated inside of a 3D object, and the bounds of the 3D object become invisible, it doesn't seem possible to add the flake to an existing metallic paint material.

I tried duplicating the original object, moving the copy slightly above the original, and applying the flake geometry to the elevated copy.

But as I feared, and as you can see below, because the flakes are above the original paint material, they are also above the clear coat. This makes it appear as if they've been sprayed on top of the clear coat, not mixed into the base coat.



More critical though, is that I need to be able to have the base color, flake and clear coat all part of the same material. Duplicating and offsetting parts is not at all feasible for how these materials will be used on a day-to-day basis.

Any input/suggestions would be greatly appreciated.

[KeyShot]

For metallic paint KeyShot introduced flakes back many years ago. The new flakes geometry is intended for volumetric materials - like flakes inside a translucent or transparent. For snow the bright lights is caused by surface reflections and as such should be created with a normal map.

[monson67]

I'm aware of the Flake feature nested under Metal Roughness in the Metallic Paint material, but I've never had any success with it. I think the Metallic Paint material has a lot of potential, and it accomplishes a look that other materials can't, in terms of blending paint colors with metal to varying degrees. But when it comes to the stochastic microfacet specular highlights from the flakes that you find embedded in actual automotive metallic paint, KeyShot falls quite short.

Here is a sample metallic paint material, alternating between turning flake on and off.

Rather lackluster, right?

I know I can apply noise bitmaps to the metal color texture, but this does not come close to replicating true metallic flake.

Esben Oxholm shared a fantastic project he worked on for Fender a couple years ago.
https://www.youtube.com/watch?v=bXElJ3139Vs
https://blog.keyshot.com/2016/animation-week-fender-pro-ear-monitors-esben-oxholm
As you can see in the material graphs (in the link above), he put a lot into giving them a metallic paint look, but without being able to produce stochastic microfacets, there are still limitations. (This is not meant to disparage Esben's work in any way. I'm just trying to find examples that best illustrate my point.)

I've also tried using normal maps to create these specular highlights, but this doesn't achieve the proper effect either.

V-Ray introduced stochastic microfacet flakes a little while back.

Look at this V-Ray example from the article I linked to earlier.
https://www.fxguide.com/wp-content/uploads/2016/10/stochastic_flakes_video.mp4
The look I really want to recreate starts at 0:40 in the video. It's got the realistic flake, but it's underneath the smooth, glossy clearcoat.

Another great, realistic example.
https://www.youtube.com/watch?v=f-xRsCWynco

Here's a study from Cornell University I found about Stochastic Microfacets.
http://www.cs.cornell.edu/projects/stochastic-sg14/stochastic.pdf
Once I got past the Abstract and Introduction, it was nothing but gibberish to me. But maybe there's something helpful there for people smarter than myself.

The point is, the new flake geometry feature in KS8 seemed like it was the missing ingredient in realistic looking metallic paint. I have no idea what it takes to develop the materials KeyShot comes up with, but I would think if you could start with the Metallic Paint material, and replace its current flake option with a thin "coating" of the new flake geometry, it could be a huge improvement.

[KeyShot]

The flakes in the metallic paint in KeyShot are absolutely capable of that. You probably need to adjust the flake size to make them visible.

[Esben Oxholm]

Hi monson.
Thanks for referring to my project. Don't mind the comments on the lacking flakes. I'm painfully aware of that today

With that said, I think that, at least from KeyShot 7 (maybe earlier too), the flakes in the metallic paint work quite well.
What are your metal coverage value in your example? That influences the visibility of the flakes as well.

Here's an (probably too extreme) example of the flakes:
https://www.youtube.com/watch?v=EWZ1DlouzW0&feature=youtu.be

Is it closer to the look you are asking for?

Cheers,

[DriesV]

It will not match the V-Ray example exactly, but I think Metallic Paint can produce pretty convincing flakes.
Here is an example scene and renderings thereof.
Click here to download the scene.

Two important considerations:

• Flakes will show more clearly with high-contrast lighting. Having a small, bright light source (e.g. sun) will help as well.
• The Photographic Image Styles in KeyShot 8 will allow to further accentuate the flakes.

I hope that helps.

Dries

[monson67]

It appears lighting was the main reason why I couldn't get the results I was looking for - both in this scenario and in the past. For the work that I do, most of the images I create will have a consistent lighting, so as to match the other product images on our website. This lighting almost always uses large light sources in the HDRI for an evenly-lit shot.

In this scenario, I was testing KS8's new Spotlight material, along with other new features, and I was confused about the results I was getting. It appears to me that physical lights don't react well at all with the flakes in the metallic paint material (I was getting the same issue with Area Light as well). I don't know if it's a known limitation or a bug, but it doesn't seem right. When I turned off the physical light and turned the HDRI back on, the flakes appeared again. I tried your suggestion, Dries, and I added a small but bright highlight to the HDRI, and got a much better looking effect from the flake. Adding that small, bright highlight explains why I never got satisfactory results from my standard large-light-source HDRIs. Though it still is not to the level of V-Ray's stochastic flakes, it is much, much better.

I attached a side-by-side image below. The only difference between them is lighting - I made no changes to the Metallic Paint material (To be clear, both have a Clear-Coat Roughness value of 0. I don't know why the one on the right appears matte). The left is only HDRI, and the right is only physical lighting.

Unfortunately, I don't know if this will work for my standard workflow/lighting environments. I do really appreciate your responses, though. And Esben, sorry if I poured salt in an old wound . The tutorials you post on YouTube are phenomenal, and you do excellent work.

[bharris]

I've also had issues with the metallic paint flakes appearing 'matte', almost like a rough anodizing. I've never thought to change lighting types, that is good to know.

[DriesV]

Hi Will,

Good find with the physical light issue. It has been filed as a bug.

Dries