# What's the point of mixing the same shader types?

Many time I've seen some material using mixing of two same nodes like this:

Is there any difference from using this?

• The roughness value is different Nov 9, 2015 at 20:36
• @Alexander Pukhalski think it's in case of altering the other shader at a later on (a normal map on the bottom one, for example). Or when you change the shader in the materials panel, some settings are preserved from the old one and this is a good example of that. Nov 9, 2015 at 20:44

They are not equivalent. Mixing two different roughnesses produces a subtly different distribution of angles at which light can be scattered:

Note the shaper highlights on the right hand example (mixed roughness).

To visualize what is going on, take this (very approximate) example:

The length of the arrows represents the amount of light that gets scattered in that direction.

• Thanks! There's a lot to learn. Where can I read about commonly used shaders and their node setups? Nov 9, 2015 at 20:45
• blenderguru.com explains each shader node option, while the pay for cycles encyclopedia goes into more detail. Nov 10, 2015 at 3:40

Late to the party but the example with suzanne is not very clear.

Let me over-exaggerate and demonstrate - these are the 2 shaders that will participate - glossy sphere with a perfect point light in front (0.0 size):

Now let's mix the roughnesses into 1 shader ((0.01+0.91)/2 = 0.465) and also mix the shaders to see the difference:

The mixed shaders doesn't produce a single "material" (no physically correct material has this roughness distribution), but they produce (simulate) two materials - a material with a glossy clear coat. That's what it is used for.

In your given example the roughness value is different. This is a common method to add two otherwise identical shaders that have different values.

• Yes, I see it. But wouldn't that be identical to just using the shader with "middle" roughness value (gloss shaders in example use .6 and .2 values, can we replace them with one shader with .4 value)? Nov 9, 2015 at 20:40
• You can use a texture to mix them Nov 9, 2015 at 20:40