Car Paint

Category: Illumination

Shader Family: Surface Material

Output: Color

Related mental ray shader: mi_car_paint_phen

The Car Paint shader simulates the unique characteristics of car paint:

Diffuse reflection in the pigmentation layer producing color shifts at edges due to viewing angle and incident light angle.
Specular highlights from metallic flakes suspended in the pigmentation layer. Including optional ray traced reflections in the metallic flakes.
Clearcoat layer with mirror or glossy reflections and specular highlights with an optional glazing mode.
All topped with a Lambertian dirt layer, if needed.

Surface

Ambient Color	The ambient light color component. This parameter is treated differently to the ambient/ambience parameter pair of many other base shaders in that it is influenced by the other diffuse color parameters on this property page. It represents incoming light, rather than the object's ambient color.
Base Color	The base diffuse color of the material.

Edge Color Controls

Color	Represents the color shift between the base color and the edge color. The color seen at the edges usually appears much darker. For really deep metallic paints as seen on sports cars, the edge color tends to be almost black.
Falloff	Defines the falloff rate of the color towards the edge. The useful range is 0.0 to 10.0, where the value 0.0 turns the effect off. Higher values make the edge region narrower and lower values make it wider.

Lit Region Color Controls

Region Color	Defines the color seen in the illuminated area of the object's surface.
Falloff	Defines the falloff rate of the color towards the light. The useful range is 0.0 to 10.0, where the value 0.0 turns the effect off. Higher values make the colored region facing the light smaller/narrower, while lower values makes it larger/wider.

Diffuse Controls

Weight	Modifies the overall level of the diffuse color parameters.
Falloff	Defines the falloff of the diffuse shading. The useful range is 0.5 to 2.0, where 1.0 represents standard Lambertian shading. Higher values push the diffuse peak towards the light source, and lower values flatten the diffuse peak.

Specular

Primary Highlight

Color	The color of the primary specular highlight.
Weight	Specifies the blend weight for the primary specular color.
Specular Decay	Defines the rate at which primary specularity decays outward.

Secondary Highlight

Color	The color of the secondary specular highlight.
Weight	Specifies the blend weight for the secondary specular color.
Specular Decay	Defines the rate at which secondary specularity decays outward.

Glazing

Enables a glazed surface effect by setting a threshold on the primary specular highlight. This option makes the surface appear more polished and shiny. To create the effect of a new sportscar with a highly waxed finish, turn Glazing on. For the look of an old, beat-up car, turn Glazing off.

Reflection

Surface Reflection

Color	The color of the reflections in the clearcoat layer of the car paint (generally white).
Facing Angle Weight	A multiplier defining the strength of the reflection at surfaces facing the camera. Set to low values between 0.1 and 0.3.

Edge Reflection

Factor	Defines the narrowness of the reflective edge.
Weight	A multiplier defining the strength of the reflection at surfaces perpendicular to the camera (edges). Clearcoat tends to reflect more at edges than on facing surfaces, this is known as a fresnel effect.

Glossy Reflection

Glossy Rays	Sets the number of glossy reflection rays to be traced. The value of 0 disables glossiness.
Glossiness	Sets the amount of glossiness. Car surfaces are generally almost like mirrors so this value should be kept small.

Optimization Settings

Max Ray Distance

Limits the reach of reflective rays.

If the max ray distance is set to 0.0, the reach of the reflection rays is infinite. For values greater than 0.0, the reach of the reflection rays is limited to this distance, and the color of the reflection is faded toward the environment color as the length of the ray approaches this distance. Use Max Ray Distance to improve performance and reduce excessive noise caused by high-contrast objects in the distance.

Optimize Environment Sampling

When off, an environment sample is made for each reflection ray that misses an object or needs to be mixed with the environment when using the Max Ray Distance option. When on, the environment is sampled only once for these reflection rays.

Flakes

Reflectivity	The color of the reflective flakes, which is generally white.
Color Weight	A multiplier for the above color.
Raytraced Reflection	Defines the amount of ray traced reflection in the flakes, which allows glittery reflections of an HDRI environment, for example. The value of 0.0 turns the effect off. The effect should generally be very subtle and a value of 0.1 is often enough. The final intensity of the reflections also depends on the reflectivity color and the color weight.
Specularity	Sets the specular exponent for the flakes.
Density	Sets the density of the flakes. The useful range is from 0.1 to 10.0, where lower values indicate less dense flakes (more flakes are given low color values near black) and higher values indicates denser flakes.
Decay Distance	Since flakes are inherently small, they can easily introduce rendering artifacts if their visual density becomes significantly smaller than a pixel. The flakes furthest from the camera may cause flicker in animation, or trigger unnecessary oversampling and long render times. To avoid this potential problem, set a distance at which the influence of reflective flakes fades out. Positive values reduce the Color Weight so that it reaches 0.0 at Decay Distance. A value of 0.0 disables any decay.
Strength	Sets the difference between the orientation of the flakes. The useful range is between 0.0 and 1.0, where 0.0 means that all flakes are parallel to the surface (which disables the effect) and higher values mean that the difference between each flake's orientation becomes larger and more varied.
Scale	Sets the size of the flakes. The procedural texture is calculated in object space, and will follow the object. Keep in mind that the scale is therefore influenced by any scale transformation on the object instance.

Dirt

Dirt Color	The color of the dirt.
Weight	The amount of dirt. This parameter would ideally be connected to a texture shader to get variations in the dirt across the surface. If Dirt Weight is set to 0.0 no dirt is added.

Advanced

Overall Shader Effect

Global Effect

Allows you to globally tune the entire diffuse, metallic flakes, and specular subsystems. It does not affect reflections or dirt.

Indirect Lighting

Global Weight

Modifies the influence of indirect light (photons and final gathering) on the object's surface. It is internally divided by PI. For example, a value of 1.0 means the standard 1.0/PI weight.

Render Tree Usage

This surface shader can be used almost anywhere in a render tree. Although it is most commonly connected directly to a Material node's Surface input (as well as Shadow and Photon), you can use any number or combination of surface shaders to control various parts of your effect. Surface shaders are often mixed (as the Base Color using a mixer shader) with textures to add realism to them. Also, you can use textures to control color inputs (such as Diffuse or Ambient) or scalar output nodes (such as gradients or fractals) to control refraction or translucency.

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