FalloffMap

The Falloff Map texture controls material blending, depending on the viewing angle of the material's geometry (figure 1). The angle between the Eye Ray and the Shading Normal is mapped from [0°, 90°] to [0, 1]. For values larger than 1, the Falloff node does a gamma correction using the Falloff Skew Factor as an exponent. OctaneRender^® uses the Skew Factor to interpolate between the spectral shades resulting from the Minimum Value and Maximum Value parameters, which are based on the first and second inputs of a Mix node. You can use the Falloff Map to control the Mix node's Amount parameter. The Mix node can either be Mix Texture or Mix MaterialThe representation of the surface or volume properties of an object..

In the following illustration, the NodeGraph Editor window is used to clearly illustrate the association of the various texture nodes.

Falloff_Map_Fig01_Rhino_v2020

Figure 1: The Falloff Map used to blend two RGB Color nodes.

Falloff Map Parameters

Mode

Normal vs. Eye Ray - This is the default mode where OctaneRender^® calculates the falloff from the angle between the Surface Normal and the Eye Ray. This mode is often used for reflections. The Falloff color range affects faces directly in front of the view, and gradually falls at angled faces towards the sides as it falls away from the straight-on viewing angle. The Falloff Direction parameter does not apply.
Normal vs. Vector 90 deg - OctaneRender^® calculates the falloff from the angle between the Surface Normal and the specified direction vector, maxing out at 90 degrees. This is similar to the default mode, except that it maintains the effect of the color range according to the Falloff Direction parameter.
Normal vs. Vector 180 deg - OctaneRender^® calculates the falloff from the angle between the Surface Normal and the specified direction vector, maxing out at 180 degrees. This provides a wider color range from the minimum to the maximum values, and maintains the effect of the color range according to the Falloff Direction parameter.

Minimum Value

The visible material on the surface facing the camera. A value of 0 displays the material connected to Material pin 2, and a value of 1 displays the material connected to Material pin 1.

Maximum Value

Determines what material displays towards the grazing angles. A value of 0 displays the material connected to Material pin 2, and a value of 1 displays the material connected to Material pin 1.

Falloff Skew Factor

Balances the Normal and Grazing angles' influence. Low values result in stronger Grazing angle influence - any textures that the Maximum Value controls cover more surface. High values result in stronger Normal angle influence - any textures that the Minimum Value controls cover more surface.

Falloff Direction

This is used by the Normal vs. Vector 90 deg and Normal vs. Vector 180 deg modes. For most materials, the Fresnel effect (the default mode) is often correct, while Falloff Direction applies for exceptional cases, which can adjust relative to the camera. Changing the object rotation will not change the Falloff Direction orientation.

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