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mental ray comes with a special shader that's designed to simulate the look of CarPaint. This is found in the Hypershade, under mental ray Materials > mi_car_paint_phen. Phen stands for phenomenon. I generally like to start with the mi_car_paint_phen_x shader. So I am going to click on this button to create the shader and then expand the Car group. I'll select the body subgroup. Right-click over the shader and choose Assign Material To Selection. Next thing, I'm going to do is I want to select the mi_car_paint_phen_x material and rename it to CarPaint.
Let's do a rRender and see how the default settings look. So this is what we end up with. It looks a little bit weird because we have some strange stuff going on here in the specular highlight, but if you understand a little bit about how CarPaint works it will help to explain what's going on. The way CarPaint is designed is we have a base color applied to the surface and then above that several layers and the topmost layer is a transparent coating. And within the transparent coating, they suspend little flakes of metal that are meant to reflect sunlight and this is what gives CarPaint its sparkling quality.
So the problem with this particular shader is that the flake size is way too big, relative to the scale of the car. So a simple way to fix that is just to reduce the size of the flakes, and this setting is found in the attributes for the CarPaint material. So I'm going to store this image and minimize the render view and in the CarPaint attributes in the Attribute Editor, I m going to scroll down to the Flake Parameters. Let me close the Hypershades, so we can see what's going on here. And the Flake Parameters determine of the quality of the flake suspended in that coding.
So the first thing I want to do is reduce the Flake Scale. The default settings 0.12. I'm going to set this to 0.002 to make it nice and small. The Flake Strength, this sets the orientation of the flakes suspended in liquid. So as this value approaches 1, the flakes become more randomly oriented so you get a little more variation in the color. You set this down to zero, all the flakes are parallel to the surface of the car and you get a kind of a different quality. So I will leave that at 0.8. Flake Decay is meant to optimize render times by not rendering the flakes that are farther away from the camera.
I'm going to leave that at zero for the moment and let's increase the Flake Density to 0.8, so we have more flakes suspended in a liquid. And the other thing I'd like to adjust is the Flake Reflect. This adds a little bit of the environment reflection to the flakes themselves. So I am just going to put this at 0.1. It isn't very strong. Let's do another render and see how it looks. So there we go. It's a little bit over the top, but you know this is a hot-rod so I think over-the-top is appropriate. So I kind of like the way that looks.
So let's store that image and take a look at some of the other settings. If I wanted to create a duller look or maybe for an older car, I might bring down the Flake Color to make it a little bit duller, and adjust some of these settings, so that they're not as present, but this is nice new sparkly paint so let's leave it that way. I want to go to the Diffuse Parameters and start adjusting the colors for the car itself. I'm of the firm belief that a hot rod should be purple so I'm going to click on the Base Color to open up color chooser and select a nice dark purple color. You can see that the preview here updates.
This is basically a more apparent on the edges that face away from the camera, leaving this at a darker color will make the car look a little bit newer. So if I raise this is going to kind of flatten out the color and make it look duller, but I want a nice new car. So the only thing I am going to do to this is click on this, and may be bring up the blue a little bit just a touch. And then the Lit Color, this is, as you can see from the preview, visible in the parts of the car that face towards the camera and it adds sort of a secondary color to it. And this can add a nice kind of variation to the color.
And you know what I think I am actually going to leave it the way it is at this kind of dark fuchsia because I like the way that looks. It should look like a good hot rod. And then of course we have to adjust the way this looks, you can adjust the Lit Color Bias. A lower diffuse weight is going to kind of flatten out the color a little bit, so I want to leave that at 1, just to keep it nice and intense. And then down under the Specular Parameters, this is going to adjust the overall shininess of the car. The default settings make this look fairly new so I am going to leave them the way they are, but you can adjust this to make the car look shinier or duller as needed.
Depending on whether you want to make a newer looking car or an older looking car. That's what we have so far. A few adjustments I think I can make it a look a little bit newer. I want to point out that the Spec Exponent and this Specular Secondary Exponent, these higher values will produce tighter highlights. So right now I have a fairly broad highlight. If I raise these values, it's going to make a tighter highlight. So I think I'd like to do that so I want to set this to 80 and this up to about 40. This secondary exponent should be a lower value than the spec exponent.
And then I think I want to bring down at the Base Color a little bit and maybe the Edge Weight. At this point it's just a matter of messing with these settings until you get what you like. Of course there is also Reflection Parameters which determine how the carPaint reflects the environment. And these are similar to Reflection Parameters found in setting in materials like the mia_material. We have Glossy Spreads. So if I increase this, it's going to spread out or blur the reflections, making it look a little bit duller. We have a Reflection Color, which is going to add a certain amount of color to the reflections seen in the surface, but I think we're going to stick with the default values and do one more render and see how it looks. There u go.
It's looking pretty good. The last thing I'd like to point out is if you encounter a situation or where you find the size of the flakes at one part of the car are a completely different from the size of the flakes in another part of the car, even though the same material is applied to all the parts of the car, you want to make sure that the scale of the car is consistent. In another words, the size of the flakes is dependent on the scale of the object. So this surface has a scale of let's say 1, 1, 1 in X, Y, and Z and maybe this part of the car has a different scaling because of something going on during the modeling process. All you need to do is remember to freeze the transformations on all the different surfaces that make up your car.
So that everything has a scale setting of 1, 1, and 1 in X, Y, Z and that should fix any problems that you have in the scaling of the flakes on the car. But there you go. That's the basics of setting up a carPaint shader. It's a lot of fun to play with, as you design your own vehicles. So try it out and see how you like it.
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