Rainbow flake effect - facing ratio to control Hue based on camera angle?

[stevesideas]

Is there any way to reproduce this effect using 3dsmax & vray? Basically I need to create a rainbow effect in the flakes that are controlled by the camera viewing angle. I guess the setup would be similar to a pearlescent type shader.

https://www.youtube.com/watch?app=de...ArvidSchneider

A real life example of the effect I'm trying to achieve.

https://www.youtube.com/watch?v=TYSv...ustomzwarriorz

[vladimir_krastev]

Hi, thanks for posting. This effect is caused by the light reflecting from the flakes and passing trough thick layer of lacquer.
I tried using a car paint material as a base layer in a blend material. The coat layer is a glass but with enabled abbe number checker. This is what I got:

I am not sure if this is the same or usefull but just an idea to consider.

[stevesideas]

Hi, thanks for posting. This effect is caused by the light reflecting from the flakes and passing trough thick layer of lacquer.
I tried using a car paint material as a base layer in a blend material. The coat layer is a glass but with enabled abbe number checker. This is what I got:

I am not sure if this is the same or usefull but just an idea to consider.

Hey. Thanks for trying this out but I'm not sure the result looks like the car paint featured in the video. Although it is producing a rainbow effect it seems that it is not over a wide surface area and only on very specific areas of the surface, creating those lines. Maybe it's an IOR thing, not sure.

[dlparisi]

I tried using a simple falloff to control the flake colors but I couldn't get a way to do that without using an OSL gradient ramp for the rainbow colors.



It kind of works like the 2nd video but I think that might be based on the angle of the surface to the light source, not the camera (I'm not sure). Regardless, scene attached. You can play with the Falloff Map's "Color Map" graph to control how the rainbow spreads across the curved surface. It's a little harsh as it's even along the curve from blue to green to red - I couldn't figure out a way to introduce some noise to colors so some of the flakes in the green area are red, etc.. I tried adding a gradient ramp to the "Flake Random Color" which helped a little but not as much as I hoped. Maybe this will help you along.

EDIT: I also wish there was a way to control the color of the flake reflections, not just the color of the flakes (as in the standard vraymtl). Ideally I think the flakes should all be the same color except where the rainbow effect is.

[stevesideas]

Those looks rather good actually. I really appreciate you spending time to have a look at this and thanks also for the file. I'll have a little play around

[kosso_olli]

Hi, thanks for posting. This effect is caused by the light reflecting from the flakes and passing trough thick layer of lacquer.
I tried using a car paint material as a base layer in a blend material. The coat layer is a glass but with enabled abbe number checker. This is what I got:

I am not sure if this is the same or usefull but just an idea to consider.

No.
The properties of the pigments create the effect. As seen in the second video, the clear coat is not involved. The rainbow effect is also visible without clearcoat.
Also, the rainbow effect is defined by the light sources, not by the camera position. In overcast lighting scenarios, the effect will not be visible. It works best in direct sunlight or at night with artificial light sources.

[Joelaff]

Can’t you set the falloff direction to “object” and then put a null where the light is (or even select the light if it lets you)?

[dlparisi]

Can’t you set the falloff direction to “object” and then put a null where the light is (or even select the light if it lets you)?

Unfortunately this doesn't seem to center the rainbow effect on the specular reflection area since this is always changing depending on the camera angle and surface normal.

[Joelaff]

From the images above it does look like the rainbow is driven by the camera based falloff. Maybe you use the light based falloff for the intensity and the camera based for the color.

[dlparisi]

I think it's all focused around the specular/light location based on this image:

If it was camera based I'd expect the rainbow to be centered a bit to the left as that looks to be pointed towards the camera a little more than the area where the specular highlight is.

If anyone knows OSL maybe this is a better route. I have no idea how to write that though.

[Joelaff]

I guess I would have to see it in person. The other two images looked more camera based. But it is hard to tell from stills. I am not familiar with this paint style, and would never put it on anything I own

[kosso_olli]

I think it's all focused around the specular/light location based on this image:

It is focused on the specular location, most definitely.