Car paint and flakes trouble (mental ray)

[Ibuilder]

Hi all,

I'm having some trouble in making a realistic metallic paint for my model. With some light colors it's not so obvious, but with this deep blue, that I'm trying on now, the flakes make the car look dirty instead of metallic.

I've tried bringing down the density as well as a tighter exponent but nothing seems to clear out that dust/dirt look on the hood. I even tried the decay distance, but the dull gray highlight still sticks on the car. What am I missing here? is it related to the reflectivity/specularity settings?

In the screen shot, the area on the right (car's left side) is ok-ish, although I could do with less dense flakes. But the real problem is the hood - as you can see it's almost completely gray.

The scene is lighted by 2 photometric lights, uniform diffuse with quite large rectangles for light source. Both diffuse and specular components are on. The hdr is currently not lighting the scene, it's there just for reflections.

Photographic exposure control is also in use.

[Domino]

wazuuuuuuuup
her eit is
the best tut ever
http://www.dmmultimedia.com/3dtips_06e4b.htm

[Ibuilder]

Hi,

Thanks, I should have mentioned that I was looking at that page already - they are very good tips indeed, but for some reason I'm not getting the same look with the flakes in my scene. I have tried copying the settings of course, but when I apply the material on the car, it only looks correct in some (viewing) angles.

So I think I have either a bad mix of light facing and edge color or something is not quite right with my specular/reflection settings - considering my lighting setup (which in turn could be the problem here).

Here are the settings for the paint in the screenshots (it's not the tutorials settings anymore, though):

[Ibuilder]

Hello,

I realized something - it's the specular component of the light that creates that "dust cover". I watched a tutorial from Jeff Patton, where he actually just turns the specular component off.

The problem is if I do that, I will get a shiny surface, but no flakes at all! How do you get both goodies? Do you actually need to setup separate lights for diffuse and specular?

[Domino]

show some renders for explanation if you can

[Ibuilder]

Ok,

Here's some:

1. both diffuse and specular components, lights are a little smaller than in the previous screens and the intensity is a little smaller too, 200 cd for each. Also the hdr giving the reflections is now also illuminating the scene, but it's a night shot, so it's a rather subtle addition.

2. same as first, but with specular turned off for all lights. The car gets really shiny, but loses the flake effect completely. They wont show even in close-ups.

3. same with diffuse turned off and specular back on. I guess this is closer to the lighting in DM Multimedia's tutorial. In my scene, the hdr lighting is not that strong so it looks a little desaturated.

Also tried: Increasing the hdr light with the multiplier and using a separate spot for the diffuse light - neither worked superbly, but I guess some sort of combination must be used. Another idea would be to use Composite to combine the effects - it might be mandatory, because the rest of the car looks best with the first option.


The hdr used in these shots is from EdenFX, supplied by 3D World Magazine.

[Ibuilder]

Something funny happened with my pngs - they look as if I had a double gamma on them in the browser. Here's a jpg version.

[Ibuilder]

Not related to paint, but the same scene - here's an example how the wheels turn out with the same lights.

At least for them, I think the diffuse and specular combined (left) wins hands down - I was having trouble getting the thread pattern to show up in the first place and messing with the lights makes it almost invisible. Of course, this is also a material issue and even a geometry issue as my thread pattern is not quite deep enough.

[Domino]

lighting problem

hdri + flakes are not good idea, dorget flakes if you are using hdri
and find some tuts about hdri light, thi is bad lighting setup, you will need only one "sky" light with hdri map in it to iluminate scene and in bg slot the same hdri map

the 3rd one looks good, try to workning on it, or have like start to next work on lights

you can upload a scene ad i can put an eye on this, maybe i will help you a little

[Ibuilder]

Thanks,

This car will be part of my portfolio - eventually - so I think I can't really upload the scene - just so that I can honestly say it was made by me from start to end, even though I have received a lot of tips from other people - but big thanks for offering your help!


I'm not sure why you say hdri and flakes are a bad idea, I don't really see a problem there. Here's a close-up of the front showing the flakes.

The hdri-lighting is based on smartIBL, although I'm not directly using it in this scene, but it's a very similar setup: The environment has a ray switcher node in it, giving a jpg for the background, crisp hi-res hdri for the reflections, and a blurred one for the FG. I plugged the "checker" (really just white) for the fall-back default, because for some reason the specular reflections of the lights (white squares) won't show up without it.

The hdri is also contributing for the lighting via skylight, which is using the environment.

I should mention that the first screen shots show up incorrectly - the thumbnails are ok, but if I open them, they look really washed out - couple of posts ago I started using jpg instead of png, so the more recent images should be ok.

[Domino]

wow i never saw this setup or what is it, i cant help with this

upload scene: i dont need your car, i just need scene setup with material and lights and model will be simple sphere, or teapot
BUT you are using Maya? i dont have Maya so can help in this way

try to play with settings you will go to your goal, dot worry you are on good way

[Ibuilder]

Thanks!

I really recommend to check out the sIBL, it's a great way to light scenes in general, although the Max version of the implementation is not as complete as some others (XSI for example). It's also free.

I'm not using Maya - I'm doing this in Max 2011. Was it the environment setup screen that made you think so? That's from the new slate material editor that comes with Max 2011. It makes it easier to see what is connected and where - although for simple materials I find the traditional material editor faster to use.

Actually, I modeled the car in XSI last summer, but I switched over to Max in the beginning of the year and imported the XSI-model over to a max scene.

I'm currently changing the direct lights in the scene - I will post some pics later!

[Domino]

Thanks!

... Was it the environment setup screen that made you think so? ...

yeah

[Ibuilder]

Alright, I'm pretty much done with this car - gotta stop tweaking at some point

Here's how it turned out, there's now just two lights with both diffuse and specular on and the hdri lighting the scene.
One light is on the side and the other in front of the car - you can tell by the flakes, which are only visible where the direct light hits them. I also tweaked the tyre material quite a bit - but it was worth it, there's no need for Composite job now.

Well, it's not quite what I wanted, but at least it's better than the starting point. Maybe I'll take another shot at it later

[Ibuilder]

Alright, I'm pretty much done with this car - gotta stop tweaking at some point

Here's how it turned out, there's now just two lights with both diffuse and specular on and the hdri lighting the scene.
One light is on the side and the other in front of the car - you can tell by the flakes, which are only visible where the direct light hits them. I also tweaked the tyre material quite a bit - but it was worth it, there's no need for Composite job now.

Well, it's not quite what I wanted, but at least it's better than the starting point. Maybe I'll take another shot at it later