The Standard shader has a secondary layer of reflection, called simply reflection, which is perfectly sharp and mirror-like. It should only be used to replicate perfect mirrors or glass shaders. If you want blurry reflections only you should use Specular.

Reflection Color

The color of the reflection ray at the current point. 

Reflection Color 0-1


Reflection

The contribution from reflection rays (the amount of light that the surface reflects).

Reflection 0-1


You will notice in the image below, that the light source is not visible in the reflection. This is because reflectivity does not sample light sources (direct light). Therefore, it is recommended that you use Specularity with glossy materials, unless a pure 'mirror' reflection is required.

In the chrome sphere below you can see the difference between the Specular and Reflection attributes when using a SkyDome light. Notice the difference between the Specular and Reflective highlights of the window in the chrome sphere and wood surface.

Reflective Caustics

This switch in the standard shader specifies whether Indirect Diffuse rays will compute the mirror reflection component.


Fresnel Falloff

Fresnel refers to reflectivity levels that occurs at different angles. Light that hits a surface at a grazing angle will reflect more than light that hits a surface face-on. The reflection level will be dependent on the viewing angle of the surface following the Fresnel equations (which depends on the IOR value). The Fresnel effect's reflection increase as the viewer's angle of incidence with respect to the surface approaches 90º. This means that surfaces rendered with a correct Fresnel effect will have brighter reflections near the edges. All types of materials become 100% reflective at grazing angles.

Fresnel Coefficient

The Fresnel effect is more noticeable when using lower values. Increasing this value gives the material a more metallic-like specular reflection. Metals have a more uniform reflectance across all angles compared to plastics or dielectrics, which have very little normal reflectance. Note that the Fresnel effect is less evident when a surface becomes rougher (the unpredictable nature of a rough surface 'scatters' the Fresnel effect, preventing the viewer from being able to clearly see it). As visible in the images below, objects rendered with a correct Fresnel effect will appear to have brighter specular reflections near the edges. 

All types of materials tend to have full reflectivity at grazing angles, as evident in the diagram below:


The examples below show various materials which require Reflectance at Normal:

For realistic materials, reflectance at normal must be lower than the specular/reflection scale (which controls the reflectance at grazing). Otherwise, you will get a darker reflection at the edges, which is exactly the opposite of the effect seen in nature. It is also not advisable to tint speculars when using Fresnel as this is not physically correct.


Note that it is also possible to map a texture to Reflectance at Normal in order to control the intensity of the Fresnel effect:


V ramp texture connected to 'Reflectance at Normal' (1 to 0). Rollover image.

Exit Color

The color returned when a ray has reached its maximum reflection depth value. 


Environment Exit Color

Specify whether to use the environment color for reflection rays where there was insufficient ray depth (true), or the color specified by reflection_exit_color (false).

 

 

  • No labels