SLIM's CORE FUNCTIONS

Layer & LayerOptimo

Description: 
Layer 
A Better Layering function that supports Maya's standard layer blend modes. Since BetterLayer is a shadingmodel template, you can connect an element to another instance of Better Layer. The implications are mind-boggling!
Layer Optimo
An efficient layering template. Shaders are much more efficient when created with LayerOptimo, however "over" is the only compositing operation available. For shaders that do not require a variety of mixes, LayerOptimo is the better solution.

Add Layer
Add additional layers for connections. The first layer will be the top level of the layered shader. Lower layers will be beneath those above them.

Connection
Reorder layers with the gray "layer" icon. 
Delete layers with the "delete" icon. 
Toggle layer visibility with the check box. 
Connect a shading model from the pull-down menu.
Mix layers in a variety of ways from the "Mix" pull-down menu, shown with all various mix types on the right.

Glass

Description:  Ray traced glass effects are simple to create with this function. Both reflections and refractions can be controlled.

Incandescence
Controls the amount of glow. Default is none.

Specular Tint
Adds a specular tint which can simulate everything from metalness to iridescence.

Specular Model
Pick from standard or glossy types of highlights.

Sharpness 
Sharpness controls the sharpness of the highlight associated with the Glossy specular model. 

Roughness
Controls the falloff of the specularity.

Index of Refraction
Controls the physical property that results in light bending when entering and leaving the material. When non-zero, this value also modulates the intensities of the reflection and refraction contributions so they sum to 1. Setting this value to zero results in no intensity modulation and allows you to control the inter-relationships of the reflection and refraction strengths entirely through the respective parameters. 

Two Sided
If your primitives have outward facing normals, you can speed up rendering by turning this switch off. If you are missing reflections, turn this switch on. 

Trace Set
A trace set expression indicating which collection of objects should be visible to reflections and refractions. 

Max Distance
The maximum distance to consider when calculating ray intersections. Setting this parameter to a negative number is effectively equivalent to setting the distance to infinity. (And a lot easier). 

Reflection Strength
Independently adjust the strength of the effect.

Reflection Tint
Adds a specular tint which can simulate everything from metalness to iridescence.

Reflection Samples
Control how many rays are shot into the scene. High quality blurred reflections required increased samples.

Reflection Blur
Blurs the ray traced effect by sending off rays within a cone, as measured in radians. Larger values create more blur, and require more samples. 

Refraction Strength
Independently adjust the strength of the effect.

Refraction Tint
Adds a specular tint which can simulate everything from metalness to iridescence.

Refraction Samples
Control how many rays are shot into the scene, when blurring refractions higher samples are required.

Refraction Blur
Blurs the ray traced effect by sending off rays within a cone, as measured in radians. Larger values create more blur, and require more samples. 

IBI

Description: 
 IBI (Image Based Illumination) uses an image in the form of an environment map as a source of illumination information. This function can be used in conjunction with a global Environment Light or independent of all other lighting conditions. IBI is designed to work with HDR (high dynamic range) images.

SurfaceColor
The coloration of the surface.

SurfaceOpacity
The surface opacity. 

Luminosity
The degree to which the surface color appears independent of lighting conditions.

Light Source
Select between an environment light or environment map for the source image. To use an environment light, attach it to objects or name it "world" to have a global effect. One environment light can effect many different shaders. For environment maps, enter the name of the particular map below.

Environment Map
Enter the name of the image for use as the environment. This will be used only if the "Light Source" parameter is set to "Environment Map."

Coordinate System
The coordinate system used to access the environment map. 

Diffuse Texture Filter
Filter of diffuse effect.

Reflection Texture Filter
Filter of reflection effect.

Lerp
Enable to smooth the transition between resolutions.

Reflection Blur
The amount of blur for the reflection.

Min Reflection
The minimum reflectivity of the surface. If your refraction index is non-zero, the reflectivity of a point on your surface will take on this value when looking down the surface normal.

Max Reflection
The maximum reflectivity of the surface. If your refraction index is non-zero, the reflectivity of a point on your surface will take on this value when looking perpendicular to the surface normal.

Refraction Index
Describes the material properties that govern the manner in which reflectivity changes with the acuteness of the angle between viewer and surface normal. If you set this value to 0 this phenomenon will be ignored and the surface will be uniformly reflective.

Reflection Coloration
Define the coloration for reflections.

Coloration Weight
The degree to which the effects of the coloration are applied.

Diffuse Blur
A value used to blur the image map. Higher values increase the "roughness" of the surface. 

Diffuse Strength
The contribution of the environment map in the direction centered on the surface normal. Generally diffuse light should be extremely blurred.

Diffuse Coloration
Define the coloration of the diffuse values..

Coloration Weight
The degree to which the effects of the coloration are applied.

Shadows
Controls shadowing effects. Shadows can come from standard direct lightsources. Direct light shadows are very efficient, but may inaccurately represent real shadowing in your scene. Indirect shadows are accurate, but can be quite expensive or, alternatively, noisy. For efficiency, you should use light links to limit the number of lights associated with IBI surfaces. If you require indirect shadows, you can speed up the shadow tests by specifying a trace subset and a maximum distance.

Shadow Filter
Takes a value for the colorization of the shadows.

Indirect Shadow Samples
When selecting indirect shadowing, this controls the quality versus speed tradeoff. More samples is slower but reduces noise artifacts. 

Trace Subset
Controls which objects participate in Indirect shadow generation. 

Max Distance
Specifies the maximum distance to consider when looking for Indirect shadows. Setting this distance to a negative number causes the renderer to consider intersections at any distance. 

For More Information:
See the tutorial -- IBI -- Image Based Illumination

Image File

Description: 
Access to an image file with an alpha channel.

File 
Choose an image file.

Associated Alpha 
If the alpha channel of your image file has an alpha that was computed with the color it is said to be associated. If the alpha channel contains an un-associated alpha, this switch will cause the color value to be premultiplied by the alpha value.

Opacity Mode
Choose between Normal and Stained Glass. If you are creating ray traced shadows through a semi-transparent colored object, switch this parameter to Stained Glass. 

S Filtering 
The amount to overfilter in the S direction.

T Filtering 
The amount to overfilter in the T direction.

Lerp
Selects whether to interpolate between adjacent resolutions of a multi-resolution texture in order to smooth the transition between resolutions. 

Mainifold 
Select an appropriate manifold.

Skin

Description: A shading model that should have a visual appearence generally similar to that of skin. Based on phenomenological information about skin reflectance from Hanrahan and Krueger, "Reflection from layered surfaces due to subsurface scattering", proceedings of Siggraph 1993. Based on the work of Matt Pharr.

SkinColor
Provides the surface color.

SheenColor
Provides the color of sheen.

Opacity
Defines the opacity of the surface.

Ka
Set the ambient value.

Kd
Set the diffuse value.

Ks
Set the specularity.

Thickness
Adjust the simulation of skin thickness. More thickness, the more the light will caught by the skin. 

eta
Control the amount of skin sheen.

Swiss Army

 Description:  Swiss Army is well suited for many ray tracing needs: reflections, refractions, sub-surface scattering, indirect illumination, caustics, etc. That's why it's called Swiss Army; it's got it all. Notice you only pay for the extra ray tracing functionality when you need to. If the intensity of a particular ray tracing operation is set to zero, no ray tracing for the operation will occur. If the intensity of a ray traced parameter is set above zero then that effect will be evaluated. That way you can create reflections via tracing, but you don't pay for any other computations like refractions, indirect illumination, etc.  

Surface Color
Set the surface color

Opacity
Set the opacity

Incandescence
Controls the amount of glow. Default is none.

Ambient Strength
Controls the effect of ambient scene lights

Diffuse Strength
Controls the effect of direct lights on the diffuse channel, Kd.

Diffuse Filter
Add additional effects to the diffuse values

Specular Strength
Controls the intensity of highlights on the surface.

Specular Filter
Adds a specular tint which can simulate everything from metalness to iridescence.

Metalness
Higher values increase "metalness" which means specular highlights will be filtered throught the surface color. Plastic objects tend to have white highlights.

Roughness
Controls the falloff of the specularity.

Reflections & Refractions
These are some typical parameters that control ray tracing from a generic shader's perspective. 

Two Sided 
If your primitives have outward facing normals, you can speed up ray tracing by leaving this switch disabled. If you are missing reflections, turn this switch on. 

Max Distance
The maximum distance to consider when calculating ray intersections. Setting this parameter to a negative number is effectively equivalent to setting the distance to infinity. (And a lot easier, heh.) An appropriate Max Distance setting can significantly speed up a scene by only doing as much work as needs to be done. Those rays that don't hit anything can reference an environment map. 

Environment Map
Add an environment map which will be used when a ray doesn't hit anything. 

Index of Refraction
You can make the index of refraction different for reflections and refractions. For the physically correct result, set these two parameters to the same value.

Strength 
When set to zero no tracing occurs. This parameter controls the intensity of the reflection. Different functions can be added here (such as a fractal function) to create interesting effects.

Reflection Filter
Filter reflections through this color. Good for creating metallic objects and other interesting looks. 

Blur
You can create interesting effects by blurring reflections. Increase this setting to get more blur, or connect a function here for special effects. Remember when creating blurry reflections you'll also want to increase the "Samples" parameter to at least 4. Larger blurs require more samples.

Samples 
For use with blurry reflections. Controls the amount of rays sampled at any given point. Higher samples increase the quality of the blur, but render slow, appropriate for final quality. Lower samples render faster and are useful for preliminary images. 

Trace Set
Trace Sets can be used to define what objects a shader will consider for ray tracing calculations. Careful use of Trace Sets can not only be extremely efficient, it can also be used for special effects, by specifying which objects are visible to any given collection of objects. Manage Trace Sets using the familiar Maya sets, with an added Trace Set attribute. 

Refractions
Refractions are like reflections only gathered from a different direction. The parameters provided for reflections are also available for refractions and can be indepedently controlled.

Sub Surface
These parameters control subsurface scattering effects. This method takes a brute force approach. You have been warned.

Strength
Control the strength of the effect. Set to zero for no ray tracing to occur.

Filter
Filters the color of the effect

Density
A control describing transport of light through an object and limited by the range defined by Max Distance. This has an exponential effect.

Max Distance
A control for the overall depth of an object. Increasing this value increases how for light penetrates an object. This value is measured in world units. 

Trace Subset
Trace Sets can be used to define what objects a shader will consider for ray tracing calculations. Careful use of Trace Sets can not only be extremely efficient, it can also be used for special effects, by specifying which objects are visible to any given collection of objects. Manage Trace Sets using the familiar Maya sets, with an added Trace Set attribute. 

Samples 
Controls the amount of rays sampled at any given point. Higher samples increase the quality of the blur, but render slow, appropriate for final quality. Lower samples render faster and are useful for preliminary images. 

Blur
The default "1" is probably a wise setting for this effect. Larger blurs, like "1," require more samples. 

Indirect Diffuse
Connect an indirect illumination function here to enable indirect illumination calculations.

Caustic Strength
Multiplier for the caustic light contribution.

Caustic Filter
Filter for the caustic light contribution.