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By comparing visual results from both LayerWeight's Fresnel and Fresnel Node on a test sphere I concluded that these settings give similar results:

Blend:  0.00  0.10  0.50  0.70  0.80  0.90  0.95  0.98  1.00
  IOR:  1.00  1.10  1.70  3.30  5.10  10.0  20.0  50.0  1000

The Y scale is logarithmic

Layer Weight node:

• Layer Weight Facing output mixes the two shaders based of angle of incidence.

• The Fresnel output mixes them based on fresnel formula (Dielectric fresnel weight), which is a function of angle of incidence. The exact math is here: Wiki

• The Blend slider adds additional blending between the two shaders: at 0 it will be green and at 1 it will be red.

  

On the other hand the Fresnel node allows for proper IOR input:

I use Fresnel node when dealing with glass-like materials, where the light goes through - where it bends at the interface. I can set proper IOR for the interface this way.

I use Layer Weight node when dealing with reflectivity, it allows for better control over the transition on the surface (how smooth it is) and over how the materials are mixed (with that blend slider). This suits artistic approach better when you are eye-balling stuff.

By comparing visual results from both LayerWeight's Fresnel and Fresnel Node on a test sphere I concluded that these settings give similar results:

Blend:  0.00  0.10  0.50  0.70  0.80  0.90  0.95  0.98  1.00
  IOR:  1.00  1.10  1.70  3.30  5.10  10.0  20.0  50.0  1000

The Y scale is logarithmic

Confirmed by Brecht (thanks) the conversion formula is:

• IOR = 1/(1 - Blend)

• Blend = 1 - 1/IOR

Layer Weight node:

• Layer Weight Facing output mixes the two shaders based of angle of incidence.

• The Fresnel output mixes them based on fresnel formula (Dielectric fresnel weight), which is a function of angle of incidence. The exact math is here: Wiki

• The Blend slider adds additional blending between the two shaders: at 0 it will be green and at 1 it will be red.

  

On the other hand the Fresnel node allows for proper IOR input:

I use Fresnel node when dealing with glass-like materials, where the light goes through - where it bends at the interface. I can set proper IOR for the interface this way.

I use Layer Weight node when dealing with reflectivity, it allows for better control over the transition on the surface (how smooth it is) and over how the materials are mixed (with that blend slider). This suits artistic approach better when you are eye-balling stuff.

By comparing visual results from both LayerWeight's Fresnel and Fresnel Node on a test sphere I concluded that these settings give similar results:

Blend:  0.00  0.10  0.50  0.70  0.80  0.90  0.95  0.98  1.00
  IOR:  1.00  1.10  1.70  3.30  5.10  10.0  20.0  50.0  1000

Layer Weight node:

• Layer Weight Facing output mixes the two shaders based of angle of incidence.

• The Fresnel output mixes them based on fresnel formula (Dielectric fresnel weight), which is a function of angle of incidence. The exact math is here: Wiki

• The Blend slider adds additional blending between the two shaders: at 0 it will be green and at 1 it will be red.

  

On the other hand the Fresnel node allows for proper IOR input:

I use Fresnel node when dealing with glass-like materials, where the light goes through - where it bends at the interface. I can set proper IOR for the interface this way.

I use Layer Weight node when dealing with reflectivity, it allows for better control over the transition on the surface (how smooth it is) and over how the materials are mixed (with that blend slider). This suits artistic approach better when you are eye-balling stuff.

By comparing visual results from both LayerWeight's Fresnel and Fresnel Node on a test sphere I concluded that these settings give similar results:

Blend:  0.00  0.10  0.50  0.70  0.80  0.90  0.95  0.98  1.00
  IOR:  1.00  1.10  1.70  3.30  5.10  10.0  20.0  50.0  1000

The Y scale is logarithmic

Layer Weight node:

• Layer Weight Facing output mixes the two shaders based of angle of incidence.

• The Fresnel output mixes them based on fresnel formula (Dielectric fresnel weight), which is a function of angle of incidence. The exact math is here: Wiki

• The Blend slider adds additional blending between the two shaders: at 0 it will be green and at 1 it will be red.

  

On the other hand the Fresnel node allows for proper IOR input:

I use Fresnel node when dealing with glass-like materials, where the light goes through - where it bends at the interface. I can set proper IOR for the interface this way.

I use Layer Weight node when dealing with reflectivity, it allows for better control over the transition on the surface (how smooth it is) and over how the materials are mixed (with that blend slider). This suits artistic approach better when you are eye-balling stuff.

Here is how Layer Weight works- the setup:

The Facing output mixes the two shaders based of angle of incidence.

The Fresnel output mixes them based of fresnel formula (Dielectric fresnel weight), which is a function of angle of incidence. The exact math is here: Wiki

The Blend slider adds additional blending between the two shaders: at 0 it will be green and at 1 it will be red, it's a fake effect.

On the other hand the Fresnel node is physically correct. It also allows for proper IOR input:

I use Fresnel node when dealing with glass-like materials, where the light goes through - where it bends at the interface. I can set proper IOR for the interface this way.

I use Layer Weight node when dealing with reflectivity, it allows for better control over the transition on the surface (how smooth it is) and over how the materials are mixed (with that blend slider). This suits artistic approach better when you are eye-balling stuff.

By comparing results from both on a test sphere I concluded that:

• Blend = 0 looks the same as IOR = 1
• Blend = 1 looks the same as IOR = 1000 (infinity)

Therefore the conversion formulas would be:

IOR = 1 - log(1 - Blend)

Blend = 1 - e^(1 - IOR)

By comparing visual results from both LayerWeight's Fresnel and Fresnel Node on a test sphere I concluded that these settings give similar results:

Blend:  0.00  0.10  0.50  0.70  0.80  0.90  0.95  0.98  1.00
  IOR:  1.00  1.10  1.70  3.30  5.10  10.0  20.0  50.0  1000

Layer Weight node:

• Layer Weight Facing output mixes the two shaders based of angle of incidence.

• The Fresnel output mixes them based on fresnel formula (Dielectric fresnel weight), which is a function of angle of incidence. The exact math is here: Wiki

• The Blend slider adds additional blending between the two shaders: at 0 it will be green and at 1 it will be red.

  

On the other hand the Fresnel node allows for proper IOR input:

I use Fresnel node when dealing with glass-like materials, where the light goes through - where it bends at the interface. I can set proper IOR for the interface this way.

I use Layer Weight node when dealing with reflectivity, it allows for better control over the transition on the surface (how smooth it is) and over how the materials are mixed (with that blend slider). This suits artistic approach better when you are eye-balling stuff.