Iso Angle shader is a very useful tool for fine-tuning surface highlights. Iso Angles are simply bands/curves connecting the points on a surface, where the normal direction at those points make a constant angle to a defined vector. In automotive design, the Z vector (vertical direction) is usually taken as the reference, as it is perpendicular to the horizon plane. Alias and ICEM Surf users are quite familiar with such diagnostic shading tools and is an invaluable part of creating high quality surfaces.

Although Blender has many "Matcap" materials to evaluate shapes, they are all view dependent. As more and more automotive designers are now using Blender, there is a need for an iso_angle tool similar to ICEM Surf/Alias.

The following is an implementation of such a Material in Blender. Thanks to the node based shaders, it is straight forward to calculate the angle between the surface normals and a perdefined axis. If N is the normal vector of a point on surface and V the direction vector, the angle θ between them can be defined as
θ = arccos( N.V/|N||V|)


The node Iso Angle Shader can be plugged to any material output.


Click here to download the .blend file.


GPL v3


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