Specular Maps and Specular in Arnold

What is Specular?

Specular is direct and indirect reflections which can be made glossy (blurred).

Specular maps can be used to define a surface’s shininess and highlight colour. The higher the value of a pixel (black to white), the shinier the in game object. Therefore surfaces such as dry stone or cotton fabric would have a very dark specular map, while surfaces like polished chrome or plastic would tend to have lighter maps.

The pixel colour is also used to calculated the resulting colour of the surface; a very saturated specular map will have very different visual effect than a grey specular map. If you need a more “neutral” highlight on a surface, your specular map should use the inverse of the diffuse map’s colour. Using the same colour on the specular as on the diffuse will result in a more saturated highlight when viewed in the game. (Wiki.splashdamage.com, 2017).

 

Specularity in Arnold

Weight

Increasing the weight, influences the highlight in the material.

standard_specular_spheres.png

Roughness

This controls the glossiness of the specular reflections- the lower the value, the sharper the reflection.  In the limit, a value of 0 will give you a perfectly sharp mirror reflection, whilst 1.0 will create reflections that are close to a diffuse reflection. You should connect a map here in order to get variation in the specular highlight.

standard_spec_roughness_teapots.png

The microscopic features of a surface alter the effect of the diffusion and reflection of the light. The microsurface detail has the most noticable effect on the specular reflections. In the diagram below, you can view parallel lines of incoming light commence to diverge when reflected from rougher surfaces, when each ray hits a part of the surface with a different orientation. In summary, the rougher the surface becomes, the more the reflected light will diverge or appear ‘blurred’.

image2014-2-25 10-31-13.png

In short- the higher the roughness, the more the light is reflected, and the more blurred the object becomes.

The brightness of the highlight is linked to its size, due to the Standard shader’s energy conserving nature. To get variation in the highlights of the surface, a map should be connected to the Specular Roughness. This will influence not only the brightness of the highlight but also it’s size and the sharpness of the environmental reflection.

Anisotrophy

Anisotrophy reflects and transmits light with a directional bias and causes materials to appear rougher or glossier in certain directions. The default value for Anisotropy is 0.5, which means ‘isotropic’. As you move this control towards 0.0, the surface is made more anisotropic in the U axis, and as you move the control towards 1.0 the surface is made more anisotropic in the the V axis.

standard_anisotropy_spheres.png

Anisotrophic 0-1. (Support.solidangle.com, 2017).

References

Wiki.splashdamage.com. (2017). Specular Maps – Mod Wiki. [online] Available at: http://wiki.splashdamage.com/index.php/Specular_Maps [Accessed 21 Mar. 2017].

Support.solidangle.com. (2017). Specular – Arnold for Maya User Guide – Solid Angle. [online] Available at: https://support.solidangle.com/display/AFMUG/Specular [Accessed 21 Mar. 2017].

 

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